CHOICES AMID CHANGE - A World Without Ice - Henry N. Pollack

A World Without Ice - Henry N. Pollack (2009)


If you do not change direction, you may end up where you are heading.

—LAO TZU Chinese philosopher, sixth century BC

Where indeed are we headed? The ark of humanity seems dangerously adrift in the sea of climate change, with no apparent navigational charts, or even a captain, on board. Can we prevent a world without ice? Can we avoid flooded coastlines? Are there pathways to the future that are less calamitous? These are straightforward questions, but ones that do not yield simple answers.


Unfortunately, there is no course of action that will freeze today’s status quo and forestall any further changes. Change is under way and is certain to continue because of inertia in both the climate system and the global industrial economy; it is impossible simply to pull the plug and stop these systems in their tracks. They each have momentum analogous to that of an aircraft carrier trying to change course—for several seconds after the helmsman turns the ship’s rudder to a new heading, the vessel plows ahead on its old course before slowly beginning to turn. In the global climate system, some of this inertia derives from the greenhouse gases we have already emitted into the atmosphere in times past, but with effects that extend far into the future. Carbon dioxide, the principal greenhouse gas, lingers in the atmosphere for more than a century, as it slowly dissolves into the ocean and is gradually consumed by green plants. These greenhouse gases will continue to warm the atmosphere and oceans even if new emissions could somehow be eliminated.

We have no illusions, however, that eliminating greenhouse gas emissions is within easy reach. Climate scientists have developed projections of how the climate might evolve if greenhouse gas concentrations in the atmosphere could be frozen at their current level, to see what changes might accompany a stabilized greenhouse. In climate science and policy circles, this idealized conceptualization of the future is called a “climate commitment.”109 Even after stabilizing the greenhouse, the inertia of the climate system will continue to drive climate change for several centuries into the future.

So what is it that we have already and unavoidably committed ourselves to? Were we able to immediately stabilize the atmospheric greenhouse at current concentration levels, Earth’s atmosphere would still warm by about one Fahrenheit degree by the end of this century. This warming would be followed by continued loss of Arctic sea ice, shrinking of the ice caps in Greenland and West Antarctica, ocean waters warming to greater depths, changes in the geography and intensity of storms and drought, and sea level rising at a rate almost twice that experienced in the twentieth century. Because this climate commitment is the outcome of an unachievable assumption—an immediate and complete stabilization of greenhouse gases in the atmosphere—we must recognize that the projected outcomes constitute an underestimate of the changes that will actually take place. In other words, the consequences that will actually unfold in this century, while still veiled in some uncertainty, will exceed those just mentioned. It is imperative, therefore, to begin planning for changes that are unavoidable, an endeavor broadly termed adaptation.


Adapting successfully to a changing climate will require fundamental and sweeping reassessments. We need to ask how a changing climate will affect everything we do, wherever we do it. For example, in agriculture the questions might include:

✵ What problems and opportunities will a longer growing season present?

✵ What will be the impact of warmer soil on seed germination?

✵ What problems will changes in water availability and timing create?

✵ Will different crops be better suited to the future climate than the current crops?

✵ Will different pests and weeds replace those present today?

✵ Will there be a need for more or fewer, or different, fertilizers?

Already researchers are looking to wild relatives of some domestic foodstuffs in search of the genetic makeup that has given these wild plants natural resiliency to drought, heat, and changes in the salinity of water.110 Other research has focused on building resiliency to extended flooding, with some strains of rice now able to survive up to two weeks underwater, compared to only a three-day survival of earlier varieties. And of course careful water management is an essential in any setting—researchers and farmers are always studying and testing new methods of irrigation.

In the public health arena, practitioners will need to think about how to cope with increased frequencies of extremely hot days and nights in crowded cities, how to safeguard municipal water supplies against bacterial blooms, how to modify sewage systems to cope with more extreme rainfall events, and how to prevent more frequent food contamination in a warmer world.

The list has no end. The transportation infrastructure of the Arctic region, long dependent on hard frozen ground or thick ice, must adapt to a softer, mushier foundation for much or all of the year. Emergency preparedness agencies will need to reshape their responses to more frequent floods, hurricanes, and wildfires, and make plans for refugees from rising seas. Electric utilities will face higher peak demands during the more intense and more frequent heat waves, while at the same time adjusting to different sources of electricity generation. City managers, urban planners, and architects will need to rethink what is required to build or reconstruct climate-resilient and energy-efficient cities, and governments of oceanfront municipalities will face zoning and building code issues along beaches and barrier islands, and infrastructure changes to their harbors. The private sector will find opportunities to provide new materials, products, and technologies.

The marine fishing industry will have to anticipate where the fish will be found as the temperature structure of the oceans changes. Freighters on the Great Lakes, in response to lower lake levels resulting from increased evaporation, will have to lighten their loads to access shallower harbors, and modify navigation to avoid hazards that once lay safely below the surface. The insurance industry is already facing a revision of its risk and rate tables as floods become more frequent, wildfires more widespread, hurricanes more intense, the storm season longer, and coastal areas more vulnerable to storm surges as sea level rises. Some insurance carriers have already pulled out of the home insurance market in Florida because climate-related threats—and the consequent cost of claims—are too great. And educational institutions at all levels will bear new responsibilities to prepare students for the demands of a changing world.

The unavoidable future also includes issues that humans have never had to think about in the past. Near the top of the list is open access to the Arctic Ocean. There is a very real possibility that in only a few decades the Arctic Ocean will be free of ice in the summertime, giving people unimpeded access to this vast region for the first time in human history. In 2007, the extent of summer sea ice diminished to the lowest ever recorded since comprehensive synoptic data have been available. In 2008, for the first time in at least a half century and probably much longer, a ring of open water encircled the Arctic—both the Northwest and Northeast passages were open simultaneously.

This physical opening of the Arctic Ocean leads to an opening of important geopolitical issues as well—the claiming of territory, the exploration for mineral and energy resources, and the exploitation of biological resources—issues that were more or less moot when the Arctic was inaccessible. The nations bordering the Arctic already have begun jockeying for position. In 2007, a Russian submersible planted the national flag in the ocean floor at the North Pole, an action reminiscent of when, a half century earlier, the USS Nautilus surfaced at the North Pole and the United States opened a scientific research station at the bitterly cold and windswept South Pole. While largely symbolic, occupancy of the pole with its central 360-degree range of vision is a geopolitical statement of control.

In 2008, the U.S. Geological Survey released a study of oil and gas potential in the Arctic Ocean. This study indicates possible Arctic oil reserves equal to three years of current global consumption, and perhaps a decade of natural gas reserves. The latter amount equals the vast land-based natural gas reserves in the Russian Arctic. Fortunately, from the point of view of potential conflicts, the USGS said that most of the reserves are located in areas on the continental shelf where national sovereignty is well established, principally in offshore Alaska and offshore Russia. The biggest exception is the Lomonosov Ridge, a relatively high submarine topographic feature that extends from Asia toward Arctic Canada and Greenland, bisecting the Arctic Ocean. Russia, Greenland, and Canada all have asserted that it is part of their continental shelf, and are seeking exclusive mineral rights under the provisions of the United Nations Convention on the Law of the Sea.

It is not just energy resources that can generate tension in the Arctic. At a time when the historical fisheries of the world have been severely depleted, the biological resources of the Arctic are becoming increasingly attractive and accessible. The countries and peoples bordering the Arctic Ocean have a long-standing dependence on food from the sea, and will welcome access to new resources. But so will many others; Japan, Korea, and China, nations with large fishing fleets, are sure to cast their eyes on—and their nets in—the Arctic Ocean. The European Union has already had discussions about how to oversee the development and exploitation of the Arctic, as well as to provide protection of the environment and the indigenous people.111 NATO representatives meeting in Iceland in 2009 discussed security challenges that might develop as the Arctic opens, and Canada has already revealed plans to build a deepwater port and a military training center in the high Arctic. Both the Pentagon and the United States polar research community have called for building a much larger icebreaker fleet to enable greater access to and better control of U.S. polar waters.112 Not to be outflanked, Russia, too, has announced plans to deploy military forces to protect its national interests in the Arctic.

To many people adaptation means planning for the long-term future, but there are some places where adaptation is already a necessity. About halfway south along the western coast of Greenland is the small town of Ilulissat, home to some five thousand residents and an equal number of sled dogs. Ilulissat, known also by its Danish name of Jakobshavn, is the third largest town on Greenland. Tom Henry, a reporter for the Toledo Blade, wanted to help his Ohio readers appreciate the consequences of climate change in the Arctic, to make sure they knew that this was as much a story about people as it was about polar bears. In 2008, Henry persuaded his publisher to send him to Ilulissat to get a look at a place where both climate change and adaptation are current realities. In the Inuit language, Ilulissat means “icebergs,” appropriately so because the town sits near the mouth of the fjord that hosts the Jakobshavn Glacier—Greenland’s most prolific ice stream. This glacier alone accounts for more than 6 percent of the ice loss from Greenland’s interior ice cap, an amount that has doubled in only the past decade.

Once in Ilulissat, in many conversations around town, Henry learned of both changes and adaptations. Most Inuits in the surrounding areas travel by dogsled over the flat surface sea ice, because much of the rugged inland topography makes for difficult, if not impassable, sledding. Unfortunately, the diminishing sea ice has effectively isolated residents of outlying settlements for much of the year. Fishermen docked in Ilulissat are finding the halibut more elusive and the catch more expensive, as the warming ocean water has driven the fish to greater, and cooler, depths. But the tourist industry is booming as visitors come to see massive icebergs break from the glaciers, and to watch whales that now cruise the area, consuming large quantities of fish species unknown around Ilulissat prior to the warming of the water.


Given that it will be effectively impossible to hold greenhouse gases in the atmosphere at current levels, what can we expect from more realistic scenarios? The answer to this question, like many other attempts to illuminate the future, are burdened by many uncertainties—uncertainties in our knowledge of how the climate system works in all its complexity, in our ability to transcribe what we do know about climate into detailed computer models, and in how we humans, major players in today’s changing climate, will respond to the challenge it presents.

The nonscientific public often has been impressed with the successes of science: the highly precise and accurate predictions of solar and lunar eclipses centuries into the future, of the comings and goings of Halley’s comet, and of the transits of Venus across the face of the Sun. Science has enabled the realization of ballistic missile intercepts far out in space, the launch and management of satellites that have revolutionized mobile communications, and the pinpoint navigation of the Phoenix Lander to Mars. Given these achievements, it’s not surprising that many people have high confidence that scientists will lead us smoothly and accurately into the future, with few surprises.

But in reality it is not an easy task to forecast the future, particularly the future of a system as complex as Earth’s climate. Such a large natural system is generally far more complicated than the relatively simple physics governing the orbits of celestial bodies and the trajectories of spacecraft. There is also a big difference between predicting the future of inanimate systems such as planetary orbits and that of a system in which humans play a very important role. When human behavior is part of the equation, the uncertainty of the outcome escalates substantially. So, when the IPCC scientists declare that global average temperature at the end of the twenty-first century will likely exceed the temperature at the beginning of the century by 3.2 to 7.2 Fahrenheit degrees, the range expresses the uncertainty not only about the climate science, but also about how the people and governments of the world will address the challenges of a warming climate.

The latter uncertainty, associated with the human responses to climate change, is sometimes called behavioral or social uncertainty. This uncertainty about the future arises first from an uncertainty about how Earth’s human population will grow over the next several decades. Over the past ten thousand years the global population has doubled almost eleven times. The most recent doubling, from four to eight billion people, began in 1975 and will probably be achieved around 2020. At the beginning of this century demographers projected the population at mid-century would reach somewhere between eight and eleven billion people, most likely around nine billion. But what a huge uncertainty that is—a difference of three billion people between the lower and upper estimates. That uncertainty is equal to the entire population of the globe in 1960. Because energy consumption is directly related to the number of people on Earth, clearly this demographic unknown casts considerable uncertainty into the mid- and end-of-century estimates of temperature increases associated with the growing use of energy.

But it is not just the number of people who will populate Earth that is uncertain—there is also uncertainty about how much energy each person will consume in the future. All peoples of the world aspire to an easier and better life, an aspiration that is usually possible via access to affordable energy. The entire history of per capita energy consumption nearly everywhere has been one of ever-increasing growth—rapid in modern industrial societies, slower in remote rural regions. The future trend, with very few exceptions, is a continuing acceleration in energy consumption. How rapidly per capita energy consumption will grow throughout the present century is another source of uncertainty in the projections of climate change.

How the energy will be generated is yet another source of uncertainty. Will it continue to come from coal, petroleum, and natural gas—the carbon-rich fossil fuels—or will it come from renewable carbon-free energy sources such as wind, solar photovoltaics, geothermal, and nuclear? A transition from fossil to renewable energy sources must traverse a minefield of politics and economics, and of regional and industrial-sector special interests. In 2009 the United States made a political transition from an administration that for almost a decade did little to move away from reliance on carbon-based energy, to an administration that appears willing to embrace non-carbon energy alternatives.


THE MOST RECENT Intergovernmental Panel on Climate Change report comprises three volumes, each about the size of the New York City telephone directory. More than two thirds of the pages are devoted to aspects of how the future might unfold. The sections of the report dealing with the consequences, impacts, and mitigation of climate change, and adaptation to it, all examine various demographic, political, economic, and technological pathways into the future. The IPCC does not have a mandate to recommend policy—its responsibility is only to make projections about the future under a variety of social scenarios.

The scenarios vary widely. At one end of the spectrum is a twenty-first century that includes high population growth, continued reliance on carbon-based energy, slow economic development and technological change, and little international integration of regional economies. This scenario, sometimes called the business-as-usual pathway, depicts an accelerating rate of greenhouse gas emissions, CO2 levels in the atmosphere that reach between three and four times the preindustrial level by the end of this century, and a range of severe climate consequences. Stephen Schneider, a climate scientist at Stanford University, calls this the “worst-case scenario.”113

At the other end of the spectrum is a scenario with a global population that peaks in mid-century at around nine billion people, and then declines slowly in the second half of the century. It depicts a rapid introduction of conservation measures and new energy-efficient technologies, widespread development of non-carbon-based energy sources, and strong growth in an integrated, globalized, and increasingly service- and information-based economy. This scenario would result in a much lower rate of greenhouse gas emissions that peak before mid-century and fall thereafter. Levels of CO2 in the atmosphere would remain below double the preindustrial level, and would produce less severe but far from trivial consequences. Several other scenarios fall between these two bookends, with variations in one or another of the demographic, economic, or technological components. The IPCC placed no probabilities on which of the scenarios, if any, will represent the way the twenty-first century will actually unfold.


For any given emissions scenario, climate scientists can project how the temperature, ice distribution, sea level, precipitation patterns, and many other aspects of climate will evolve in the future by simulating the entire climate system on a powerful computer. The radiant energy from the Sun; the aerosol and dust loading of the atmosphere; the current distribution of ice and vegetation around the globe; the equations of heat and mass transfer in the atmosphere, oceans, soil, and rocks; and how they interact and make exchanges with one another and with terrestrial life forms—all are represented in hundreds of thousands of lines of computer code. Given a particular input emissions scenario, what comes out of a simulation is the climate of the future, as envisioned by the scientists who write the computer code. In other words, the climate projections are the output of a computer “model” of the global climate system constructed by a group of climate scientists.

Many scientific groups around the world have developed such models, some with great complexity, others with less. Each model expresses the best judgment of the science team creating it—judgment about how to simplify complexity without sacrificing accuracy, about how to represent computationally awkward equations more simply, about how much regional detail to strive for without unduly increasing the time it takes the computer to do the calculations. These different judgment calls lead to different projections for the climate.

Which of these different model projections, describing conditions a century or more into the future, will prove to predict the evolution of the climate with the greatest accuracy? We cannot know, because the future has yet to unfold. To fully appreciate why projections of the future are always expressed in terms of a range of outcomes, we must assess the uncertainty not only associated with the different social scenarios, but also that arises from differences among the climate models. Blunt, definitive statements that declare “this is the way it’s going to be,” without any mention of uncertainties or probabilities, should always be viewed with suspicion.

Because models represent the real world incompletely and imperfectly, and yield predictions that are embedded in uncertainty, we must always evaluate the predictions with careful scrutiny. Following computer models with unwavering rigidity can lead to cliffs of disaster. We need only think of the highly touted financial models that failed to foresee the partial collapse of the securities and capital markets in 1998, and the near-total paralysis and failure of these markets again in 2008. Both collapses had a common theme—most banks failed to recognize the fragility of their loan portfolios. This myopia, however, can be traced to the economic models that underestimated the risks associated with all kinds of loans, and lured banks, hedge fund managers, and investors big and small onto thin economic ice. That ice eventually and dramatically gave way, sending the entire global economy to depths not experienced for many decades.

George E. P. Box, a well-known statistician at the University of Wisconsin, once stated bluntly: “All models are wrong. Some are useful.” To extract utility from models, one must always be skeptical of their structure, and strive to recognize their likely limitations. Emanuel Derman and Paul Wilmott, two experienced builders and users of economic and financial models, assert that the most important questions about any model are, What does it ignore and How wrong is it likely to be?114

These caveats about financial models apply to environmental and climate models, too. Orrin Pilkey, a coastal geologist at Duke University, says that computer models of shoreline retreat in the face of rising sea level115 don’t even approach reality. I, too, have some reservations about the way many climate models handle the heat exchange between the soil and atmosphere. And my University of Michigan colleague Joyce Penner, also a contributing author to the IPCC assessment reports, offers a well-informed opinion that most global climate models fail to represent fully the complex effects of atmospheric aerosols on the radiative forcing of the climate system. But neither Penner nor I categorically reject climate models because of their imperfections—we both recognize their utility, indeed their necessity, in spite of their current limitations.

In a wide variety of fields, computer models are extremely versatile quantitative tools used with great success. Meteorologists now employ computer models to give us very reliable forecasts of the weather up to a week in advance, and to plot the likely trajectories of hurricanes as they approach populated areas. Geologists use sophisticated numerical models to map the likely subsurface pathways of plumes of contaminated groundwater, and petroleum engineers employ computer models to determine the optimal exploitation of oil and gas resources deep beneath the Earth’s surface. Even the future reliability of stockpiled nuclear weapons is determined in part with complex computer models.

The hard reality is that computer models are the only effective tools we have to explore quantitatively the large range of possible scenarios about how future climate change will unfold. We should not be dismayed by the imperfections of the models, or distracted by the uncertainties surrounding the results. Just because scientists, demographers, economists, and policymakers don’t know everything, that doesn’t mean that they know nothing. They clearly do not operate in a state of complete ignorance; to the contrary, they have substantial knowledge in their fields of expertise. With an appropriate dose of humility that openly acknowledges uncertainties in a straightforward way, and encourages repeated probing for weaknesses in the structure of the models, climate models will continue to be very useful and instructive.


All too frequently one hears skeptics or politicians present uncertainty as an excuse to avoid making important policy decisions. It is important to recognize, though, that postponing important decisions because of uncertainty is actually just an implicit endorsement of the status quo, and often an excuse for maintaining it. It is a fundamental bulwark of the policy known as business-as-usual. Waiting for climate change uncertainties to disappear is not a feasible option, because much of the uncertainty, particularly the social uncertainty, will never go away. We cannot know with certainty what the population will be fifty years from now, nor can we know with certainty what technological innovations will emerge.

Can we expect that future research will yield a better understanding of how the climate system works? Can we anticipate bigger and faster computers that will require fewer compromises in the climate model computing codes? Yes, we certainly will see improvements over time, but they are unlikely to lead to significantly improved model projections that would make the wait worthwhile. Improved climate models that might narrow the range of policy options will be of little help if the improvements come only after the policy opportunity is no longer an option. Uncomfortable as it may be, important policy decisions about how to mitigate and adapt to climate change must be made in the face of considerable uncertainty about the future.

In my 2003 book Uncertain Science … Uncertain World, I write about how uncertainty both permeates and motivates science, and how it subtly influences people’s everyday activities as well.116 Whether we realize it or not, uncertainty is something we live with and adjust to all the time. Robert Lempert and his colleagues at the RAND Corporation, in a book with the intriguing title Shaping the Next One Hundred Years: New Methods for Quantitative Long-Term Policy Analysis,117 expand these concepts to identify bedrock principles for developing sound long-term policies in the face of deep uncertainty. They reframe the question “What will the long-term future bring?” into a different question: “How can we choose actions today that will be consistent with our long-term interests?” In other words, they provide guidelines that help decision-makers, faced with deep uncertainties, to make sound policy without having answers to every important question.

Because there is deep uncertainty about the future, Lempert and his RAND colleagues argue that we should not try to predict the long-term future with precision, because too many surprises lie beyond the horizon. Winston Churchill captured this perspective when he said, “It is a mistake to try to look too far ahead. The chain of destiny can be grasped only one link at a time.” We need to explore a wide range of scenarios about how the future might unfold, and to seek strategies that do well in many different scenarios. Finally, we must monitor the impacts of policy actions, and the changing conditions in which the policies are being implemented—and make mid-course corrections as necessary. We learn a lot about how complex systems work by watching how they behave. When the system behavior deviates from a desired pathway, it is time for a mid-course correction to realign the system behavior with our goals. This flexibility is called adaptive management, and it will be critical if the world is to confront climate change effectively.


In 2009 the concentration of carbon dioxide in the atmosphere reached 390 ppm, and was increasing by 2 to 3 ppm each year. The IPCC’s assessments of the impacts of higher temperatures due to increasing levels of CO2 and other greenhouse gases indicate that serious problems in freshwater availability, ecosystem disruption, food production, coastal erosion, and public health—already emergent today—will be very apparent when the level of atmospheric CO2 reaches 450 ppm. One does not need higher mathematics to recognize that at the current rate of emission—the business-as-usual scenario—CO2 will reach that level before mid-century, and will continue climbing to even higher levels. The clock is ticking, even as we debate the best course of action.

If we are to have a chance of averting the worst of the consequences of climate change and ice loss, policymakers must make major decisions soon, even without answers to many important questions. Serious reductions in greenhouse gas emissions, described earlier in the more aggressive alternative to the business-as-usual scenario, must take place over the next few decades. Why? Because the lifetime of carbon dioxide in the atmosphere is long, and a few decades of delay will impose centuries of consequences. After the United States squandered most of this century’s first decade with a business-as-usual climate policy, there is no time to waste in implementing new energy and climate policies that include serious emission reductions. Such a proactive step is called mitigation.


The shadow of an uncertain future, possibly one with extraordinary changes that have severe consequences, provides a motivation for a rapid reduction in and eventual elimination of the human causes of climate change. The principal focus of mitigation is to slow and then reverse the loading of the atmosphere with anthropogenic greenhouse gases. The mechanisms of mitigation are many—some make use of existing technology and are available immediately; others require development of new technologies and will come online later.

Conservation and Efficiency

At the very top of the list of mitigation options are energy conservation and efficiency measures in transportation, manufacturing, household appliances, and buildings. Benjamin Franklin famously said that “a penny saved is a penny earned,” and that concept applies to energy consumption as well—a kilowatt-hour saved is a kilowatt-hour that need not be produced, and a gallon of gasoline not used represents dollars that stay in a driver’s pocket. The cheapest energy is always the energy that one does not use.

According to researchers at the Lawrence Livermore National Laboratory, more than half of all the energy produced in the United States is wasted.118 Two thirds of the energy used to generate and distribute electricity is lost before it ever reaches a home to light a bulb or heat a stove. The personal transportation sector—cars and light trucks—wastes more than 70 percent of the energy contained in gasoline, and the American manufacturers have been notoriously slow to improve fuel efficiency. Imported vehicles have captured an increasing share of sales in the United States for almost half a century, and now account for more than half of the American market. To be sure, the causes of declining market share for American automobile manufacturers go beyond just excessive fuel consumption. But it is fair to argue that the U.S. auto companies’ long resistance to higher fuel economy standards hastened the decline of recent years. A doubling of automobile fuel efficiency of American cars is already possible utilizing existing hybrid technology. Even a tripling could be achieved by reducing the weight of vehicles through use of strong, lightweight composite materials. Today, in addition to the driver, most vehicles move at least a ton of steel down the highway. In essence, most of the fuel these vehicles consume goes toward moving themselves, and only incidentally their occupants.

If Americans, indeed people everywhere, were to drive fewer miles each year, they would accrue substantial fuel savings and emissions reductions. Less driving could be achieved in part with greatly expanded high-quality public transportation. Many cities in the United States have been slow to provide viable alternatives to driving personal vehicles. Where such alternatives exist, however, millions of people take advantage of them on a daily basis. The subway in Washington, D.C., which opened in 1976, has become the second busiest rapid transit system in the United States, trailing only the New York City subway. The success of the Washington Metro, as well as newer, well-used light-rail systems in Dallas and Minne apolis, show that a clean, reliable, frequent, and safe rapid-transit system can be a very attractive alternative for many urban and suburban commuters. Even the older, somewhat dysfunctional system in New York remains the most practical, cost-effective choice for millions of daily riders.

If the trend toward suburban housing with long commutes to work could be reversed, more fuel savings and emissions reductions could be achieved. What might promote such a reversal? A revitalization of attractive, affordable housing in city centers. The enduring success of New York as a vital city is in no small part because people live, buy their groceries, do their shopping, and go to school and work in neighborhoods throughout the city—a majority of them without even owning a car.

Fully 40 percent of America’s energy consumption is associated with the buildings in which they live and work. Efficiency and conservation measures in the heating and air-conditioning of buildings offer potentially large energy savings. Furnaces, air-conditioning units, and many household appliances are available today that operate well above 90 percent efficiency, in contrast to older units that struggled to reach 50 percent. And upgrading home and building windows and insulation to keep more of winter’s cold and summer’s heat outside is a low-tech improvement with a rapid payback.

Carbon-Free Energy

Energy sources that do not produce greenhouse gases are of course attractive mitigation options. The carbon-based fossil fuels—coal, oil, and natural gas—are in effect stored solar energy from ages past. All are derived from ancient life forms composed in part of carbon, energized by sunshine, and sequestered underground for millions of years. It should be no surprise that direct utilization of modern sunshine is a principal hope for carbon-free energy.


Solar radiation has long been used for direct heating of living spaces and domestic water, but it can also be collected at an industrial scale to produce steam to drive electrical generators. Additionally, solar radiation can be converted to electricity directly by photovoltaic devices, better known simply as solar cells. These devices already provide electrical power for myriad small applications—hand calculators, cell phones and portable radios, sailboats, road signs, remote scientific instruments, and much more. At rooftop scale, solar cells can provide a nontrivial fraction of domestic electricity, even where half the days are cloudy. Improving the efficiency of solar cells is an important and promising research area—today’s solar cells convert only about 20 percent of the incoming solar energy into electricity, leaving lots of room for improvement.


Uneven solar heating on a planetary scale creates differences in atmospheric pressure. The atmosphere responds by pushing air from high-pressure areas to places with lower pressure—a motion we call wind. In places where the wind is strong and steady, there is great potential for generating abundant electricity. Long used in windmills and water pumps, the ubiquitous wind has in recent years fostered development and deployment of modern wind turbines in large “wind farms.” Denmark produces about 20 percent of its electricity from wind, and the United States about 2 percent. The technology is improving rapidly, and cost reductions have already made wind price-competitive with carbon-based energy. Wind is the fastest-growing source of new energy-generating capacity worldwide, particularly in Europe and the United States.


Hydroelectric power generation at large dams on big rivers, the modern equivalent of hydropower from water wheels, today provides almost 20 percent of the world’s electrical energy. But its potential for growth is limited; most of the best locations already have such installations. The tidal movements of ocean water are in a few places driving electrical generators, and researchers are developing prototype devices driven by river currents. Emerging technologies will also soon capture the up-and-down motion of waves along some coastlines to generate electricity.


When atomic bombs brought World War II to a sudden end, the world witnessed the almost unimaginable energy unleashed from the nucleus of fissionable elements. In weapons, the energy is liberated in explosive fashion, but the process of splitting a nucleus can also be controlled to liberate energy in a slow and steady stream. Worldwide, nuclear energy generates about 14 percent of the global electricity. In the United States, the world’s largest producer of nuclear-generated electricity, about 20 percent of the nation’s electricity comes from nuclear installations. France generates more than three quarters of its electricity using nuclear energy, but even that large fraction of France’s electricity is less than the electricity generated by U.S. nuclear plants. The expansion of nuclear-generating capacity around the world faces several hurdles, including the very high capital costs of construction, a need for large volumes of water to cool the reactor, operational safety concerns, and the complex challenges of securely storing waste that will remain dangerously radioactive for thousands of years.


Just ten feet below the surface, Earth barely feels the seasonal oscillation of the surface temperature, from winter to summer and back again. The temperature at that depth sits stably at the year-round average of the surface temperature. In winter the underground temperature is higher than at the surface, and in summer it is lower. That characteristic, a subsurface temperature that does not change seasonally, is the basis for geothermal home heating and cooling systems. In winter, heat is extracted from the warmer soil to heat the house, and in summer heat is removed from the house and returned to the soil. Essentially the system is a two-way heat pump that exchanges heat with the surrounding soil via water circulated through a closed loop of buried piping.

Another type of geothermal energy is the heat contained in very hot rocks near volcanic magma, in places only a few hundred feet beneath the surface. This extreme subterranean heat can produce both hot water and live steam that can be captured to heat buildings or generate electricity. The Geysers Geothermal Area, seventy-five miles north of San Francisco, provides much of the electricity for coastal California north of the Golden Gate Bridge. In Iceland, the island nation located in the middle of the Atlantic Ocean just south of the Arctic Circle, geothermal waters warm most of the houses and buildings. Even without nearby magma, the temperature of rocks everywhere rises with increasing depth beneath the surface. These warm rocks are also viewed as a potential source of thermal energy to heat water for industrial and domestic use.


For millennia, people have burned wood to provide heat and light, and later to generate steam to power machinery. But trees are only one of many plants that can yield energy through combustion. It may seem counterintuitive that biomass offers possibilities for mitigation of greenhouse gas emissions—after all, plants have much the same carbon-based composition as the ancient plants that comprise coal. But the production of energy from biomass does in principle provide emissions mitigation, because it just recycles carbon dioxide—extracting it from the atmosphere as the tree or plant grows, and returning it to the atmosphere when burned as a fuel—with zero net increase in atmospheric CO2. By contrast, burning of ancient coal sends fossil carbon into today’s atmosphere, and is thus a net addition of CO2. But not all biomass has the same energy content, and not all processes to extract that energy are equally efficient. For example, ethanol produced from corn—after taking into account all the energy needed to grow the corn and produce the fuel—is barely a break-even operation. Corn-based ethanol has another downside: diversion of cropland and a primary edible grain into energy production, thereby exacerbating the daily reality of hunger for tens of millions of people around the world. Fortunately, other non-food vegetation, including some hardy weeds and even green algae growing in bodies of water, hold considerable promise as biomass fuel sources.

Capturing Carbon

With an enormous amount of coal available around the world, many ask if there could not be a way to continue using that abundant resource, but somehow prevent the combustion products, including CO2, from escaping into the atmosphere. Can we not somehow capture the CO2 and contain it harmlessly somewhere? Trapping carbon and storing it safely is the dream of the so-called “clean coal” campaign.

Storing carbon may be the easier half of this mitigation strategy. Storage, or sequestration, takes two forms: biological storage and geological storage. Plants store carbon as they grow. Hardy forests, with trees that live many decades or even centuries, are in effect warehouses holding significant carbon. About 20 percent of the CO2 growth in the atmosphere is attributed to worldwide cutting of forests; consequently, slowing or reversing deforestation could take a substantial bite out of the steady growth of atmospheric CO2. Carbon can also be stored directly in the soil, with attendant benefits to both the soil and the atmosphere.

Geologic sequestration involves pumping of CO2 underground into rock formations with sufficient tiny pore spaces to accommodate large volumes of the greenhouse gas. Natural gas companies already use underground storage to adjust supply to meet seasonal demand. Gas produced in the summer is stored underground, to be available during the peak demand of winter. This storage strategy has been well tested—nature has stored natural gas underground for millions of years. Several field tests are now under way in rock formations beneath the North Sea and at several sites in the United States and Canada, to test the practicability of large-scale CO2 storage. Deep ocean basins have also been considered as repositories, because liquefied CO2 is denser than seawater at the pressures encountered in that environment. But issues of long-term stability and of changes in ocean chemistry have yet to be resolved.

In order to store CO2 it must first be captured. The technology to pull CO2 from smokestacks where it is generated, or directly from the atmosphere where it accumulates, is still in its infancy. A joint industry-government project launched in the United States in 2003 to demonstrate the feasibility of “clean-coal” electrical generation, complete with carbon capture and storage, continues but has not yet reached a proof-of-concept stage. Small pilot projects using a variety of technologies to capture carbon show promise, but the difficulties in full-scale development and deployment remain.

Slowing Population Growth

The extraordinary growth of the human population in the twentieth century, along with each person’s ever-growing appetite for more energy, has made humans the greatest agent of change on Earth. Obviously, one approach to reducing the demand for energy would be to slow the rate of growth of Earth’s population. The number of people on Earth of course plays a big part in the human footprint on the planet, as noted in chap ter 6. But discussions of population levels have never been formal agenda items at any international conference addressing climate change. There simply are too many political and religious pressures that have kept population planning off the table for discussion or negotiation.

WILL THESE VARIOUS mitigation strategies be fast enough and comprehensive enough to rein in greenhouse gas emissions over the next two to three decades? All mitigation strategies have strengths and shortcomings, proponents and detractors. If the long debates about whether to require higher fuel efficiency in automobiles or where to store nuclear waste are any indication, the urgency of confronting climate change may be blunted by political pushing and pulling that in the end may deliver too little, too late.

Debates about which of the mitigation strategies offers the best chance of reducing emissions miss the point: we need them all. If we hope to avert the harsh consequences of climate change, we need every horse in the stable pulling together, and as hard and as fast as possible. Ironically, the severe global economic instability that began in 2008 may promote a greater willingness to take bold steps that may dramatically reshape America’s energy infrastructure and industrial economy. On the other hand, the economic distress might instead serve as an excuse for further inaction on climate change. That would be a tragedy of historical proportions, because there truly is no more time to waste.


Because the future is burdened with uncertainty, we must be particularly observant of the way the real world is behaving, and always be assessing how well the model projections compare with reality, how well the assumptions implicit in the model continue to be valid. Consider the simplest type of model projection of some quantity X into the future—one in which the rate at which X changes remains steady, and so the cumulative change in X is just proportional to the passage of time. In technical terms, this is called a linear extrapolation, because a graph of the changes in X over time will be a straight line, upward sloping if X is growing, and downward sloping if X is decreasing.

How likely is it that the processes affecting X will continue to change at the same rate? There is no rule of nature that requires such a linear relationship to continue forever. Just as a small tree branch will bend a little when a boy steps out on it, and will bend a little more when his girlfriend joins him, everyone knows that there is a limit to the loading, beyond which the branch no longer bends—it snaps. Slow, incremental change may lead to greater and more rapid change as some limit is approached or crossed.

Scientists look for evidence of changes in the rate at which things are happening—either slowing down or speeding up. Such changes are called decelerations and accelerations. Changes in rates are often the first hint that a system is no longer behaving as it did before, and may be about to change abruptly and dramatically. For example, we should be very alert to increasing rates of atmospheric and oceanic warming and ice loss.

Year-to-year observations of Earth’s vital signs are providing much evidence of accelerating changes. The average rate of warming of Earth’s atmosphere over the past 150 years has been almost 0.1 Fahrenheit degree per decade, but the rate of warming over only the past century is 60 percent higher than over the 150-year period. And over more recent intervals, the acceleration is even greater—during the past 50 years, Earth warmed 2.8 times faster than the 150-year rate, and over the past 25 years, almost 4 times faster.

The use of energy in the United States has also accelerated throughout the twentieth century. For every unit of energy consumed by a person at the beginning of the century, by 1960 the per capita consumption was four times greater, and by the end of the century it was almost seven times greater. Because the growth of population over the century is already taken into account in per capita statistics, this acceleration in energy consumption is wholly attributable to changes in standard of living and lifestyle—driving more and in bigger cars, eating more food transported over longer distances, and living in bigger houses with more electrical appliances.

On the population front, it took more than 10,000 years for the population to reach 1 billion people. But it took only 130 years more for the population to reach 2 billion, and another 32, 15, 13, and 12 years for it to reach 3, 4, 5, and 6 billion. Between 1980 and 1990, the growth in Earth’s population averaged more than 80 million each year, the highest growth rate in all of human history. But since that decade, there is a hint of deceleration. The annual population increments have begun to decline slightly—in 2004, population grew by about 75 million—and the United Nations is projecting a continuing decline in the growth rate, to roughly 30 million additional people per year by mid-century.119

Not surprisingly, the growth in atmospheric CO2 reflects both the population and energy consumption trends. The Keeling curve that shows the growth of atmospheric carbon dioxide over the past five decades (shown on page 184) also shows acceleration in the growth rate. When Keeling first started his measurements, the rate of growth was just under 1 ppm per year, but today the CO2 level is increasing at more than 2 ppm per year, a doubling of the rate of growth in just a half century. The rate at which sea level is rising is also accelerating. In the fifty-two years from 1961 through 2003, sea level rose almost four inches, one third of which occurred in the last decade alone. Sea-level changes, of course, are related to ice loss from the continents and warming of the deep oceans, so an increase in the rate at which the seas are rising implies faster rates of ice loss and ocean warming in recent decades.

The extent and thickness of Arctic sea ice are both diminishing at ever-faster rates, and although the loss of sea ice does not directly raise sea level (sea ice is already floating), there are important indirect effects that do lead to rising seas. Less Arctic sea ice in the summer means that more ocean water is exposed to absorb solar radiation, and the refreezing of this warmer water will take place later in the fall. And newly frozen sea ice, thinner than sea ice that survived the summer breakup, will also break up earlier the next summer. Earlier breakup and delayed refreezing results in a longer warming season for the open ocean water. This warming eventually mixes into the deeper ocean and leads to sea level rise through thermal expansion.

And as discussed in chapter 7, glacial ice from Greenland, the Antarctic Peninsula, and West Antarctica is being delivered to the sea at accelerating rates. The ice shelves that impeded ice loss from the continents have been disintegrating rapidly in the last decade, allowing land-based ice to spill into the sea and raise sea level. This speedup in the flow of ice to the sea came as a surprise to glaciologists 120 and led the Intergovernmental Panel on Climate Change to caution in its 2007 report that its projections of future sea level did not take into consideration the possibility of rapid changes in glacial ice dynamics. Because the 2007 IPCC estimate of twenty-first-century sea-level rise, less than three feet, did not include any contributions due to accelerated delivery of land ice to the sea, that estimate clearly must be recognized as a rock-bottom estimate, which may well be exceeded.

Only a few years have elapsed since the IPCC report appeared, and it may already be outdated. In a special 2009 assessment121 of possible sea-level changes in the twenty-first century, the U.S. Climate Change Science Program pointed out that since 1990, the global rate of ice loss has been more than double the rate observed from 1961 to 1990. If ice spillage to the sea continues throughout this century at the rate observed in its first decade, enough ice will enter the oceans to raise sea level three feet. And to that rise must be added the thermal expansion of the seawater as the oceans continue to warm—an effect that will raise sea level at least as much as the new ice does. Both effects together will raise sea level some six feet in the present century, compared to a rise of less than a foot in the twentieth century.

Are there hints of other unpleasant surprises in the near future?


Just as the international financial system surprised the world with a major collapse in 2008, the global climate system, with its human component, is equally capable of serious surprises. Lurking in the shadows of climate change is the possibility that the accelerations we now observe in the climate system are portends of approaching tipping points.

Tipping points represent changes in a system that occur when the system passes from one mode of behavior to another, sometimes imperceptibly, sometimes suddenly. A simple analogy is the process of paying off a home mortgage. Each monthly mortgage payment comprises both interest and principal. In the early years of the mortgage, the payoff of the loan principal is painfully slow and annoyingly incremental, as most of the monthly payment goes to paying the interest on the loan. In a typical thirty-year home mortgage, a homeowner, after ten years of payments, has paid off only 10 percent of the loan. After twenty-one years of payments, the monthly check is finally split evenly between interest and principal, a tipping point that typically passes without recognition or acknowledgment. But beyond that tipping point the reduction of the unpaid balance accelerates, and as the mortgage approaches payoff, there is a rapid erosion of the remaining unpaid loan. At the end there is another tipping point, impossible not to notice—a very abrupt transition to a new state in the homeowner’s personal finances, when there is no mortgage payment to make at all.

In the climate system there are several possible tipping points: major realignments of oceanic and atmospheric circulation, rapid releases of greenhouse gases now trapped in permafrost and in the ice that exists at shallow depths beneath the ocean floor, and sudden changes in sea level. All these possibilities are related to changes in Earth’s ice.

What role does ice have in taking the climate across a tipping point? The average temperature of a planet’s surface depends directly on the amount of incoming solar energy absorbed by the surface. But not all the solar radiation delivered to Earth is absorbed—some is reflected back to space. Snow and ice are both highly reflective substances, and so the fraction of Earth’s surface covered by snow and ice is a big determinant of Earth’s average surface temperature. The more radiation that is reflected away, the less energy remains to warm the planet. Currently, Earth reflects about 30 percent of the arriving solar radiation back into space.

When the amount of snow and ice cover changes over time, so does the balance between reflection and absorption of solar energy. As ice increases on Earth, more solar energy is returned to space and less is absorbed, thus lowering the surface temperature. More ice promotes a cooler planet, and a cooler planet encourages the accumulation of even more ice. This interaction is called a positive feedback, and leads to an ever-faster acceleration of climate change. Diminishing ice cover also drives a similar feedback, but in the other direction: as Earth becomes darker and less reflective, more solar radiation is absorbed, the planetary surface grows warmer, and a warmer planet leads to even less ice cover and a further acceleration in warming.

How do the ice-climate feedbacks lead to tipping points in the climate? As we have just seen, the loss of sea ice in the Arctic Ocean is allowing much more solar radiation to be absorbed in the Arctic summer, causing a warming of the Arctic Ocean. But the principal circulation pattern of the Atlantic Ocean is strongly dependent on dense Arctic seawater sinking to make room for the warm surface current—the Gulf Stream—traveling northward from the tropics. Increased summertime warming of Arctic seawater, however, makes the water more buoyant and less inclined to sink. As this Arctic warming continues, eventually the Arctic seawater will not sink. When that happens, there will be no room in the Arctic for warm water coming from the south—and the Gulf Stream will weaken or shut down. The consequence? A deep and enduring chill would descend over Western Europe.

It may seem counterintuitive that warming of the Arctic could lead to a cooling of Western Europe, but Europe occupies a latitude band roughly similar to central Canada and central Asia, regions with much harsher climates. Europe is warmer than those colder regions because it draws heat from the warm waters of the Gulf Stream. A slowdown or shutdown of the Gulf Stream would again place Western Europe into the refrigerator, as during the Younger Dryas episode 12,700 years ago, when the Gulf Stream was interrupted and European temperatures dropped by about ten Fahrenheit degrees. What starts as a local phenomenon in the seawater of the high Arctic quickly affects the circulation of the entire Atlantic Ocean and the climate of Europe.

Another feedback with the potential to similarly alter Atlantic currents relates to the melting of the Arctic permafrost. Melting of this permanently frozen ground across vast expanses of Canada, Alaska, and Siberia is already under way. The melting provides more freshwater to flow into the Arctic Ocean via the Mackenzie River, which drains much of western Canada, and the Lena, Yenisei, and Ob rivers, which drain northern Asia. Because freshwater is also more buoyant than saltwater, the Arctic Ocean, already more buoyant because it is warming, is being made even more buoyant by the increased freshwater input from the melting permafrost. The warming and freshening reinforce each other to impede the sinking of Arctic Ocean water, and thereby slow the Gulf Stream.

How likely is this major change in oceanic circulation? The IPCC simulations show several scenarios projecting a 25 percent slowdown in circulation by the end of the century, but none that project a complete collapse. But even with a slower oceanic transport of heat to the high latitudes, the increased greenhouse warming of the atmosphere will likely compensate, and spare Western Europe from cooling, at least for a while.

The melting of the permafrost has the potential for yet another major impact on the climate system—the release of large volumes of the greenhouse gas methane to the atmosphere. Strengthening the greenhouse effect would lead to more atmospheric warming, which in turn would lead to continued reduction of the permafrost, more methane release, and thus an even hotter greenhouse. Another vast source of methane lies trapped in a form of ice present in sediments at shallow depths beneath the ocean floor. But if the ocean water warmed sufficiently to release the methane trapped in the ice, the methane would quickly bubble to the surface and lead to an even stronger greenhouse.

The existence of the methane-bearing seafloor deposits is well established, and the geological record hints that these deposits were destabilized around 55 million years ago,122 producing a stronger atmospheric greenhouse by an amount roughly equivalent to all the carbon that has been released to the modern atmosphere since the beginning of the industrial revolution. This intensified greenhouse caused Earth’s surface temperature to rise some nine to fifteen Fahrenheit degrees—a hot spell that lasted for more than 100,000 years. This event, which geologists call the Paleocene-Eocene Thermal Maximum, was probably the last time Earth was entirely without ice.

What is the likelihood of a sudden methane release occurring in the near future? Methane has been observed bubbling out of the continental shelf into the Arctic Ocean in many places, and out of the permafrost in Siberia as well. But the physical processes by which permafrost and subsea ice can be destabilized are generally slow, and thus large and abrupt releases seem unlikely. Submarine landslides can expose and rapidly destabilize the methane-bearing formations, but the geographic extent of landslides is usually small. Most simulations of methane liberation from the seafloor show it will not even begin until the ocean bottom water warms by a few degrees, and then the release will likely extend over tens of thousands of years. Fortunately, that is a slow process, unlikely to accelerate.

How stable is Greenland’s ice? Several computer simulations of future melting there show a temperature threshold beyond which the Greenland ice sheet passes a point of no return. Once that threshold is crossed—probably in this century—the melting will have such inertia that the Greenland Ice Sheet will likely disappear completely, in a relentless meltdown extending over several hundred years. Beyond that tipping point, the surface of Greenland will inexorably show more rock and less ice, and shorelines will relocate as sea level rises. And by then there will be nothing humans can do to stop it. To return to the nautical analogy, it would be like watching two ships at sea approaching each other, belatedly realizing they were on a collision course. Even though both may frantically try to steer a new course to avert colliding, they have passed the point when course corrections can take hold in time—their inertia will drive them on to the collision.

Those simulations assume that melting is the only way that Greenland will lose ice. They do not take into account the possibility of bulk ice loss to the sea prior to melting—an omission that is becoming increasingly questioned in the face of the current acceleration in the delivery of bulk ice to the ocean. The observed acceleration of ice loss from Greenland, the Antarctic Peninsula, and West Antarctica is putting to rest the idea that in order to raise sea level, land ice must first melt and the meltwater then flow to the sea. We are seeing the early stages of glacial ice sliding directly into the ocean at a rate much faster than it is being replenished by snowfall inland, an observation that strongly suggests another acceleration may be soon apparent—a further increase in the rate that sea level is rising. An ominous message comes from coral reefs that were living 120,000 years ago, during the very final stages of the warm interglacial interval that existed prior to the most recent ice age. These reefs experienced an eight-foot rise of sea level in only fifty years, most likely due to extremely rapid sloughing of ice into the sea.123

Greenland is undergoing both increased melting over its surface and a speedup of ice delivery to the sea. In Antarctica, save for the Antarctic Peninsula, the climate is generally much colder than in the Arctic, and surface melting rarely occurs. But much of the ice along the perimeter of East and West Antarctica sits directly on the ocean floor; with only modest thinning, some of this grounded ice could begin to float, lifting off the seafloor and admitting water beneath the ice. Glaciologists have long known that what happens at the base of a glacier affects the speed at which it flows over the land, but they are only now learning how dramatically the loss of ice can be affected by the incursion of seawater beneath. Effectively the seawater erodes the ice from below, just as warm air can melt it from above. Such an attack from below would almost assuredly lead to an acceleration of ice loss from the interior and faster rises in sea level.

The implications of a rapid acceleration in ice loss from Greenland or Antarctica are profound. The ice in each region alone could contribute more than twenty feet of global sea-level rise; together they could raise sea levels over forty feet, enough to submerge a three-story building. This incursion of seawater would flood coastal cities around the world, and transform New York into New Venice. Only 120,000 years ago, in the warm interval before the last ice age, Greenland lost half its ice and sea level rose ten to fifteen feet. Some three million years ago, during the Pliocene warm interval, sea level was one hundred feet higher. The much smaller and more mobile human progenitors living near the sea at those times adapted simply by moving to higher ground. There were no permanent structures, and certainly no cities anywhere.

But the world today is very different. Millions of people now live at the ocean’s edge, in many of the world’s largest cities, from Shanghai to New York to Buenos Aires. These modern urbanites might be able to accommodate and adapt to a twenty- to forty-foot rise in sea level over a thousand years, but they would find it nearly impossible to deal effectively with such a rise in only a century, let alone in a few decades. The differences between these scenarios are stark: on the one hand a perhaps orderly adaptation of physical and social infrastructure to an evolving global problem, versus a rapid physical and social disintegration leading to chaos the world over. And the difficulties will not be confined to the shoreline—cities farther inland at higher elevations will be spared the direct inundation, but not the flood of refugees and the resulting social stress arising from the dislocation of hundreds of millions of people fleeing the encroachment of the sea.


Confronted with rapid changes in so many of Earth’s vital signs, and well aware of the possibilities of impending tipping points and climate surprises, there are some who think that the mitigation measures now on the table will inevitably be a day late and a dollar short. They believe that only planetary-scale “climate engineering” offers hope of averting the worst of climate change consequences. Who are these people, and what do they propose?

These would-be climate engineers are not kooks from the fringes. The list includes respected scientists such as Michael MacCracken, the former director of the U.S. Global Change Research Program; Tom Wigley, a senior atmospheric scientist at the National Center for Atmospheric Research; Ken Caldeira, an atmospheric scientist at the Carnegie Institution, Gregory Benford, a physicist at the University of California-Irvine; and Paul Crutzen, co-recipient of the 1995 Nobel Prize in chemistry—all smart, serious people very worried about Earth’s changing climate. Crutzen’s Nobel-winning research illuminated the complex chemistry of how the man-made chlorofluorocarbons led to the development of the ozone hole over Antarctica. It was likely an important step in the evolution of his thinking about how humans have become the dominant agents of change on Earth—and his embrace of the term Anthropocene to describe the rapid ascendancy of humans in geological history.

So what kinds of large-scale “climate engineering” projects do these scientists have in mind? Their proposals fall into two broad categories: the first addresses ways to prevent sunshine from reaching Earth, and the second focuses on ways to speed up the processes by which Earth stores carbon. The several sunscreen schemes generally try to increase Earth’s reflectivity—by sending many millions of tiny mirrors into high orbit, or by spraying seawater into the atmosphere to nucleate more cloud cover, or by shooting sulfate aerosols into the atmosphere to simulate the Sun-blocking effects of volcanic eruptions. There has even been the tongue-in cheek suggestion that we should no longer try to curtail industrial pollution of the atmosphere, the logic being that dirty air and smog allow less sunshine to reach the Earth’s surface. Critics of these sunscreen approaches to climatic amelioration point out that these schemes do nothing to mitigate other environmental consequences of rising carbon dioxide levels, particularly in the oceans, where the trend toward acidity continues, and the marine biosphere is being stressed.

One idea for enhancing carbon storage is large-scale fertilization of the oceans with iron. Theoretically this would stimulate the growth of phytoplankton—organisms that pull CO2 out of the atmosphere for nourishment, thereby diminishing the greenhouse effect and cooling the planet. Small-scale experiments with iron fertilization do show some enhanced phytoplankton growth, but much of the additional biomass soon decays and returns the captured CO2 to the atmosphere. A second storage proposal would add calcium to the oceans to react with dissolved CO2, to promote the formation of limestone. In effect, this would amount to a speeding up of the geological weathering process that Earth’s natural thermostat uses to supply calcium to the sea. After precipitating limestone, the oceans then pull CO2 out of the atmosphere to replace the CO2 used in making the limestone, thereby reducing the strength of the greenhouse and slowing climate change.

But there is considerable and justified concern about potential unintended consequences of such global engineering. To cast a medical analogy, these proposals would be classified as experimental drugs, with unproven efficacy and perhaps unanticipated side effects. We have to be very careful that the cure is not worse than the disease. More than normal caution should be attached to these large-scale engineering schemes, with which we have little relevant experience. Recall that the problem these ideas might ameliorate, the change in Earth’s climate brought by the consumption of fossil fuels, is itself an unanticipated side effect of an inadvertent geochemical experiment—the removal of long-sequestered underground carbon to burn for energy, and allowing the resulting oxidized carbon to take up residence in the atmosphere and oceans.

IS IT THE FATE of the world to lose its ice? If an ice-free world comes to pass, future generations will gaze over vast areas of the planetary surface that have not seen the light of day or felt the warmth of sunshine for thousands or even millions of years. They will see the drab, gray rock beneath Greenland and Antarctica slowly rebound from deep topographical depressions imposed by the heavy load of glacial ice. But these same generations will also watch low-lying areas of the continents being flooded by the sea—areas that have not been submerged beneath the ocean since the Pliocene, or the Paleocene, or the Cretaceous, or perhaps ever. These generations will be forced to confront the political and social challenges of the millions of climate refugees displaced inland.

Some observers see climate change as the greatest challenge the human race has ever faced. They ask if humans, indeed the entire planet, will survive. I do not worry about planet Earth surviving—it has survived many challenges over its long history, including significant impacts by wayward meteorites, asteroids, and comets. I have little doubt that Earth will be making its annual journey around the Sun for millions if not billions of years into the future. So planet Earth itself should not be described as fragile. Rather, it is the great diversity of life that has evolved on Earth—a web that supports human civilization—that is at risk. As the great tectonic plates slowly moved continents, reconfigured oceans, and uplifted mountains, opportunities for new life emerged and the vulnerabilities of some existing life forms were exposed. Some life flourishes amid the stimulus of great geological changes, while other forms falter. The almost seven billion people constituting Homo sapiens are soon to be tested.

Imagine, as did geologist Don Eicher, all of Earth’s history as events compressed into a single calendar year:124

On that scale, the oldest rocks we know date from about [late January]. Living things first appeared in the sea [in February, and continents began to assemble and drift about the globe in early March. All of the major phyla of marine life had evolved by mid-October, and the generation of petroleum followed soon thereafter]. Land plants and animals emerged in late November and the widespread swamps that formed the great coal deposits of the world flourished for about four days in early December. Dinosaurs became dominant in mid-December, but disappeared on the 26th [shortly after the time the Rocky Mountains were first uplifted]. Manlike creatures appeared sometime during the evening of December 31st, and the most recent continental ice sheets began to recede from [the Great Lakes area] and from northern Europe about 1 minute and 15 seconds before midnight on the 31st. Rome ruled the western world for five seconds from 11:59:45 to 11:59:50. Columbus [reached the New World] three seconds before midnight, and the science of geology emerged with the writing of James Hutton just slightly more than one second before the end of our eventful year of years.

In this compressed perspective of our planet’s long 4.56-billion-year history, we humans show up only in the early evening of December 31. In our extremely brief time on Earth we can look at our achievements with some pride—but we must also look at our missteps with trepidation. What might arguably be called our greatest success—the creation and distribution of almost seven billion of us around the world—is also the root of our greatest challenge. It is not altogether clear that the human race has the vision, determination, or discipline to meet the self created challenges of climate change and rising seas, or to make the choices that will preserve the social structure that we call civilization. Will later intelligent life forms judge our brief time on Earth, the Anthropocene, only as an excessive New Year’s Eve party, which ended at midnight? Or will we humans enter a new era, perhaps with a hangover, but also with a sober resolve to find a sustainable path to the future? The choice is ours.


Peoples around the world have of course confronted challenges and made their choices in the past. As colonists in the New World, Americans decided to shape their destiny by breaking away from Great Britain to become a new nation. Only a decade later, the citizens of France rejected centuries of monarchy and chose a democratic path to the future. In the twentieth century, the people of Russia experienced a cataclysmic end to feudalism, and then embarked upon another seven-decade social experiment with communism that ultimately failed as badly as their feudal monarchy did. Today China is engaged in a great social transformation, to a new and not yet fully defined future. All of these changes followed a long and slow accumulation of seeds of instability that eventually crossed thresholds and unleashed rapid change. These all were challenges among people, within the human social structure—none was a confrontation between humans and the natural world.

Now we are immersed in another disruption of the human social fabric—the global financial crisis. It has caught the attention of the world like a whack to the head with a two-by-four. Just as in the earlier political revolutions, the financial instability that became abruptly apparent to everyone in late 2008 was preceded by decades of slow, largely unnoticed erosion that allowed the global economy to pass a threshold into painful collapse. The warnings from a few economists of an impending burst of the financial bubble went unheeded—as are the warnings of today’s climate scientists about ice loss and rising seas. As the financial crisis continues to unfold, it is exposing the many unsustainable and risky practices that slowly undermined the world of global finance. But in forcing a review of what led to financial instability, the crisis also is providing an opportunity to develop a clearer vision, one that may enable us to see the interconnectedness between the financial world and the natural world.

History may describe the collapse of the global financial system in 2008 as the meltdown of the twenty-first century. But history will also record that another and ultimately far more significant meltdown—the loss of ice the world over—was already under way. The money spent rebuilding the global financial system, as great a sum as it seems to be, will pale in comparison with the cost of adapting to the warmer world with higher seas and destabilizing human dislocations that will come, if effective and timely mitigation measures are not implemented.

Stephen Schneider describes two types of policy mistakes we can make in confronting climate change. The first, which in the world of risk analysis is called a Type A mistake, would be to spend a lot of treasure to address serious climate change, only to find that as the twenty-first century unfolds, climate change turns out to be much more benign than it first appeared. The second, a Type B mistake, would be to adopt a wait-and-see policy, and then discover too late that climate change consequences are every bit as severe or even worse than predicted, thus requiring big expenditures for adaptation and amelioration. Both will turn out to be expensive mistakes, but the second type, leading to widespread loss of life and property, is much more expensive and socially destabilizing than the first.

The rapidly diminishing cohort of business-as usual proponents is betting that taking no action is the right action. In what amounts to yet another of their trenches of denial, they assert that mitigation and adaptation measures are cures that we don’t need and can’t afford. If the consequences of climate change indeed turn out to be benign, they will be proven correct. However, the IPCC reports and even more recent assessments give very low probabilities to a benign eventuality. By contrast, the proponents of immediate and strong mitigation and adaptation strategies want to make substantial expenditures soon to forestall the worst of the consequences, and they will be proven prescient if climate change hits society very hard.

The U.S. government has for years feared making the first type of mistake, spending money on something we may not need. Only now is it beginning to refocus and think about the brutal economic and social costs of even moderate climate change, and how much greater the consequences will be if we do not address them quickly and aggressively. If indecision continues, however, and mitigation opportunities are missed, we will reach another “silent” tipping point where many more dollars will need to be shifted from mitigation to adaptation, an even more expensive proposition.

Some have called the financial crisis and the climate crisis an unfortunate juxtaposition—they lament that because each is such a large problem, the world cannot possibly afford to address both simultaneously. This is simply the latest version of the old canard that asserts that improvements to the environment will lead to lesser profits and loss of jobs. In truth, the juxtaposition of the financial and climate crises has presented an unusual opportunity to rethink the totality of how we interact with the natural world, and in so doing improve both the economy and the environment. Globalization of the economy and globalization of the environment have not developed independently, nor can breakdowns in each be effectively treated independently.

One often hears that the financial crisis may lead to the rebuilding of long-neglected physical, industrial, educational, health-care, and financial infrastructure, but unless it also stimulates new thinking about how we interact with our natural environment, the rebuilding will be incomplete and ultimately unsuccessful.

Al Gore argues that what many perceive as three separate problems—the financial perils stemming from the United States being the world’s largest debtor nation, the security risks rooted in our growing dependence on foreign oil, and the global dangers of a changing climate—are in reality three different facets of a single problem: an inadequate and misguided national energy policy. Treating each as a separate problem will slow progress in solving all of them, whereas recognizing them as manifestations of a single problem can lead us to develop a faster and more comprehensive solution. That is a multidimensional opportunity that we must not allow to pass us by.

LAO TZU, the ancient Chinese philosopher, once warned that in the absence of a change in direction, we will very likely end up where we are headed. That captures the essence of this moment in human history. The only climate policy Americans saw from their national government in the first eight years of the twenty-first century was a stubborn commitment to business-as-usual, a policy that brought the ark of humanity eight years closer to the dangerous shoals emerging from climate change. But it is not too late to steer a new course into the open sea of opportunity. Although the inertia of our ark will surely carry us closer to danger, a sharp change of heading today will steer us away from calamity at mid-century.

Although this challenge is new, history holds instructive lessons about ways people have coped with imminent danger in the past. The American response to the surprise attack on Pearl Harbor in 1941 has relevance to our current challenge of confronting climate change—it demonstrated that once a problem gets our attention, we can muster both the determination and resourcefulness to rapidly confront it. Immediately after Pearl Harbor, the United States entered World War II and quickly transformed a peacetime industrial economy into one completely focused on meeting the challenges of a global war. Domestic manufacture of consumer goods ended abruptly, and within months American industries were turning out airplanes, tanks, jeeps, and ships in astounding numbers. By the end of 1943, just two years after the United States went to war, more airplanes were built at a single factory in Michigan than in all of Japan. That should give us confidence that when people understand the severity of a situation they can refocus sharply and master the challenges they face.

But who is steering the ark of humanity today? In a sense, we all are. Just as billions of people through their individual actions have inadvertently caused Earth’s climate to warm, so can we humans reverse this dangerous trend. In truth, however, it will not be easy, and will require us all to do much more than just replacing our old incandescent light bulbs with newer energy-efficient fluorescent bulbs. If we hope to preserve the climate system that sustains us, we must revisit individual decisions about where we live and work, about how much space we require to live comfortably, about energy consumption and conservation in our homes, about our transportation choices, about how frequently we travel, and about how many children we will have. Those are all issues that we can address as individuals, as consumers, and as families.

But we need also to augment individual mitigation efforts with changes that can come only from collective action. We need to amplify our individual voices by joining with others to have larger-scale impacts. And there is no bigger megaphone for our voices than the ballot box at election time. The right to choose the people who will run our governments is the most significant tool we have to turn in a new direction. As individuals, we have little voice in determining how the electricity that comes to our homes is generated. But our collective voice can, through the actions of our government, determine how the energy we use is produced and distributed. Individually we have little control over tax incentives and regulatory controls—that playing field is the domain of government. Only governmental action can landscape that field to end the advantages long held by the coal and petroleum industries and offer incentives for investment in conservation and renewable energy. New government policies could place limits on greenhouse gas emissions and promote employment opportunities in enterprises that enhance rather than compete with the natural environment. Only government has the tools to reshape the regional development and transportation policies that would help us reintegrate into the natural world, and to abandon policies that unconsciously encourage us to live separate from it.

Government policies determine the level of support for scientific research, and for science education in our schools, both important elements in meeting the challenges of climate change. Only government can shape a foreign policy that encourages and promotes international cooperation in addressing global problems, including trade policies that set emissions reductions as a precondition of international commerce. And unless governments are willing to provide more educational opportunities for women, and address the cultural and religious taboos that encumber family planning in many places, little progress will be made in slowing population growth.

Many governments and institutions, however, are not agents of change. Instead governments often act only as custodians of stability, and strive to protect the status quo. That is the very definition of inertia. Governmental and institutional inertia, however, fundamentally derive from personal inertia. If we as individuals do not strive for new directions, our institutions will simply carry us in the direction we are headed—toward dangerous irreversible climate change. Our voices need to be aggregated in many settings—schools, universities, religious congregations, labor halls, civic service organizations, investment clubs, corporate shareholder meetings—anywhere and everywhere we can shape public debate. Government offi cials everywhere, whether elected or not, must hear that people want and need a new course—because without that message, little will happen.

There is a Native American proverb that says we did not inherit Earth from our ancestors, but have only borrowed it from our children. Will we selfishly repay our children with a degraded planet devoid of ice, with seawater washing over our great coastal cities? Or will we pass on a planet that has been rescued from that fate by its people—the same people who inadvertently initiated climate change, but who also recognized their responsibilities to reverse it before the worst of consequences had drowned their shorelines?

Climate change is an intergenerational problem, centuries in the making, yet many people around the world do not even understand that there is a problem, much less that it is rapidly reaching levels of serious consequence. They do not see the growing momentum of the climate system carrying us to unavoidable consequences, a momentum that without mitigation will make even more severe changes irreversible. People in all walks of life and in all regions of the world need a wakeup call, before rising seas lap at their doorsteps.

The world needs to chart a bold course into a new sea of sustainability. Whether Americans like it or not, the United States must provide a clear compass for the global family of nations, through direct and proactive leadership. While it is true that the problems of climate change are not solely American-made, it is also true that there will be no effective solutions without our full engagement. Much of the world is waiting to see what we do, and we must respond boldly, confidently, and quickly. Winston Churchill described a pessimist as a person who “sees difficulty in every opportunity,” and an optimist as one who “sees opportunity in every difficulty.” While our journey to the future will surely encounter some turbulent seas, we—like Magellan and Columbus centuries earlier—must never lose sight of the fact that we are sailing out onto a sea of unbounded opportunity. Let us all be Churchillian optimists in recognizing opportunity, and at the same time pragmatic realists in addressing the difficulties we will encounter along the way.

We have our work cut out for us. Carpamus diem!—Let us seize the opportunity!