Visitors to Greenland’s ice sheet, 2008; photograph by Olaf Otto Becker

Bill McKibben’s new book is a passionate appeal from a writer who has dedicated his efforts to warning of the risks posed by human-driven climate change. It describes the challenges we face—whether from effects on the environment that are already occurring, or from those that will occur due to the greenhouse gases we have already emitted and are likely to emit in the coming decades—if we do not act to curb emissions. But while McKibben insists on the importance of strong action to reduce those risks, he struggles to find grounds for optimism and often tilts toward a pessimism that has characterized recent works by other environmentalists, such as James Lovelock.

The title, Eaarth: Making a Life on a Tough New Planet, sums up McKibben’s main theme: we have now altered the climate to such an extent that the planet as we knew it no longer exists, and it should have a new name, Eaarth. The idea that we should find a way of acknowledging the fundamental impact that humans have had on the earth is not new. Paul Crutzen, who shared the Nobel Prize for chemistry in 1995 for showing how chlorofluorocarbons, then common in aerosols, caused the hole in the ozone layer, suggested ten years ago that the current geological epoch should be called the “anthropocene” in order to “emphasize the central role of mankind in geology and ecology.”

In 2007, McKibben launched “350 .org,” a group that advocates the need to stabilize concentrations of carbon dioxide in the atmosphere at 350 parts per million, and thus stay as close as we can to the levels occurring over the last few thousand years during which we created our civilizations. That is compared with the preindustrialization concentration of about 280 parts per million. The trouble is that the current concentration is about 385 parts per million, according to the US government’s Carbon Dioxide Information Analysis Center. And when other greenhouse gases, such as methane, are taken into account, the overall level is about 435 parts per million of carbon-dioxide-equivalent. For this reason, many of the policies for controlling climate change that have been proposed so far focus on stabilization at 450 parts per million of carbon-dioxide- equivalent as being the best we can do to limit the great risks from climate change.

We are likely to exceed that level within the next decade but, with strong action, concentrations of greenhouse gases could peak in this decade and, over a long period of time with continued strong action, return to 450 parts per million or below. But if we carry on with something like “business as usual,” we may reach concentrations by the end of the century that would imply a significant chance, perhaps as high as 50 percent, of a rise in global temperature of 5˚C or more above its level in the nineteenth century. This would be a temperature that has not been seen on the planet for more than 30 million years (Homo sapiens has been here for only around 200,000 years). The map of where people could live would probably be radically redrawn. This could imply, for example, that some areas would become deserts, some would be inundated, and many subject to radical change in weather patterns or in the location and flows of rivers. This could mean in turn the movement of hundreds of millions or billions of people. History suggests that movements of people on such a scale would likely involve extended, severe, and global conflicts.

McKibben explains that his conclusion about climate change draws on a presentation by the distinguished NASA scientist James Hansen at a scientific conference in December 2007 in which he claimed that 350 parts per million should be the upper limit for atmospheric concentrations of carbon dioxide, and that we have already passed a level that could be described as “safe.” With not much immediate prospect for returning below 350, McKibben’s book is an attempt to outline how our lives must change because “the earth that we knew—the only earth that we ever knew—is gone.”

In the opening chapter, he assails the reader with an array of statistics and facts about changes that are already visible in an effort to counter what he sees as misguided attempts to portray climate change as a problem only for future generations. Most of his catalog of consequences is supported by extensive footnotes. McKibben, however, might be criticized for relying too heavily on media reports rather than scientific references. Some of his opponents will no doubt seek to undermine the book by disputing a figure here or a fact there. But his overall thesis that we are already seeing widespread effects of climate change is sound and supported by much robust scientific evidence.

A careful consideration of the scientific analysis and evidence indicates that there is indeed a very powerful case that the risks from unmanaged climate change are immense. It was in 1824 that Joseph Fourier observed that the surface of the earth was much warmer than it would be without its atmosphere. About 150 years ago, John Tyndall showed through a series of experiments that the presence of gases such as carbon dioxide was responsible for creating the greenhouse effect—the trapping of sunlight as heat by the atmosphere.


By the end of the nineteenth century, the Swedish scientist Svante Arrhenius had begun to calculate the potential magnitude of warming that would result from an increase in greenhouse gases in the atmosphere. And by the mid-twentieth century, some of the physical mechanisms behind the greenhouse effect had been understood. Essentially, the molecules of certain gases oscillate in a way that interferes with longer-wavelength radiation that arises when solar energy is reflected back from the earth’s surface, with the result that the solar heat is trapped in the atmosphere: in the 1940s, Walter Elsassar transferred into meteorology insights of quantum mechanics from the 1920s and 1930s concerning absorption.

We now know that the concentration of carbon dioxide in the atmosphere is more than a third higher than it was before we started to burn coal and other fossil fuels on a major scale with the advent of industrialization, and higher than it has been for at least 800,000 years. As a result, the global average temperature has started to rise, by about 0.7˚C in the past one hundred years. And temperatures will continue to rise for at least the next couple of decades purely in response to current levels of greenhouse gases, even if we stopped emitting them today. With this warming come changes not just in weather and temperature extremes, but, crucially, changes in levels and distributions of water: storms, floods, droughts, river flows, rises in sea level. In other words, changes in the fundamental historical determinants of how and where we live our lives.

Thus the greenhouse effect is not some airy and speculative attempt to explain some mysterious correlation. It is basic science built over nearly two hundred years. The evidence has been accumulating in the laboratory and by observation, reinforcing both the underlying theory and the understanding that the effects are major. This evidence includes ice core data, extending back 800,000 years, that allow approximate estimates of both carbon dioxide and temperature, more detailed instrumental temperature records for the past 150 years or so, and more precise recent measurements of greenhouse gas levels in the atmosphere.

This is no Kuhnian paradigm, teetering on the edge of acceptability and requiring constant ad hoc adjustments and add-ons to sustain it as more and more difficult evidence emerges. On the contrary, this is a scientific finding with a sound theoretical foundation that grows ever stronger as evidence of many different kinds accumulates. It is the various claims by skeptics that are clearly ad hoc and unable to explain the data, such as the claim that it is all a consequence of urban heat islands, or short-term fluctuations from El Niño and La Niña, and so on. None of these attempts can explain a strong underlying global trend.

At the same time, we must recognize that predictions must be in terms of risks, uncertainties, and probabilities. There is uncertainty about future emissions, about the possibilities of absorption of greenhouse gases by the land, forests, and oceans, about the magnitude of warming from changes in greenhouse gas levels, and about the effects on local climates around the world. The issue for policy is how to manage risk, taking account of strong scientific evidence that the risks are potentially very large. These are not small probabilities of something nasty, but large probabilities of something catastrophic.

To deny the urgency of strong action in the face of all the evidence is unscientific, irrational, and dangerous. It is unscientific because it dismisses sound science and evidence built over a long period. It is irrational because such denial would require more than just querying some aspects of the science. It would require great confidence both that the scientific findings are wrong and that the risks are small, since the consequences of being mistaken in assuming that the science is right or that it is wrong would be very different.

Acting as if the scientific evidence were wrong would lead us to concentrations of carbon dioxide carrying immense risks if the science were right. Acting as if the scientific findings were right might lead us to excessive investment in developing low-carbon technologies and protecting forests if the findings turned out to be wrong; but these actions are nevertheless likely to have very substantial other benefits in energy security, energy efficiency, biodiversity, and so on. Finally, denying the urgency of strong action is dangerous because the process by which emissions become concentrated has a ratchet effect, and delay in action results in higher concentrations and a more difficult “starting point.”


There is much more scientific work to do, and many uncertainties are likely to remain, but the evidence is overwhelming that the risks are large and that delay will be dangerous. The weight of this theory and evidence is no doubt why those who deny that greenhouse gases cause climate change have to resort to tactics similar to those used a few decades ago to dispute the impact of smoking on health. One such tactic is to find one or two weak or erroneous scientific papers among the many thousands of good ones and use them as an implied smear on all the rest. Another is to make use of the irrational argument that the remaining uncertainties imply that the best hypothesis is to assume that the risks are negligible. Another is to try to deliberately confuse trends and cycles. There will be cycles and random events but the underlying trend is strong. And as in the case of smoking, there are powerful vested interests ready to fund the sowing of the seeds of doubt.


Nancie Battaglia

Bill McKibben, 2009

In the second and third chapters of his book, McKibben lays out his analysis of how we have arrived at the current situation, and identifies the moment in the 1970s when it would have been possible to chart a different path. McKibben’s words convey genuine sorrow as he explains how the drive for economic growth based on hydrocarbons in the following decades has led the planet to the point of breakdown.

The opening three chapters of the book create an apocalyptic vision that almost begs the question why we should bother trying to reduce emissions now, and it is only in the final chapter that McKibben offers any glimpses of optimism. He blames the pursuit of “national projects” of ambitious growth for not only exacerbating climate change but also creating the prospect of an energy crisis as oil reserves dwindle. His solution is a return to local economies on a smaller scale with the objective of durability rather than expansion.

McKibben tells a powerful story with great clarity, deep conviction, and lively prose. For someone from outside the United States, however, it is sometimes frustrating that he offers a perspective on the global challenge of climate change that is almost exclusively focused on the US. There is no doubt that action by the US, the second-largest total emitter and one of the highest per capita, is vital if the world is to collaborate in reducing emissions on the scale required. Other countries look to the US for leadership, in view of its wealth, technologies, and high current and past emissions. But action has been slowed by skepticism among the public about the magnitude, or even the existence, of the problem, a skepticism often fostered by the distorted arguments of some with powerful interests in maintaining “business as usual.” The United States is a crucial audience.

But while McKibben describes how climate change is affecting his home state of Vermont, he misses the opportunity to highlight the fact that those who are being hit hardest and soonest are poor and vulnerable people in developing countries. In this respect, his attack on economic growth, while perhaps having some appeal for those living comfortably in the rich countries, provides no realistic way forward for developing countries. For billions of people, economic development is the only way out of poverty and McKibben will alienate many with his dismissal of the concept of sustainable growth. There is no doubt that economic development must be understood as much more than rising consumption as conventionally measured. At the same time we must see that advances in education, health, environment, and other dimensions of development are, in many circumstances, much easier to realize if consumption and income are growing.

At a number of points, McKibben praises as “ahead of the curve” the 1972 publication of Limits to Growth, commissioned by the Club of Rome, with its emphasis on exponential economic growth running into fixed constraints, such as the availability of oil. Here is a basic analytical and practical issue on which I would differ from McKibben. The way forward to the low-carbon economy requires finding new ways of consuming and producing, and in particular replacing hydrocarbons. This means innovation and investment in new technologies and activities that can save resources while producing no greenhouse gases or actually removing them from the atmosphere.

The possibilities of finding substitutes for hydrocarbons and making “green” technological progress were grossly underemphasized in Limits to Growth. Thus the assumptions that allowed its authors to claim that growth can, will, and should end are precisely what we must now counter in order to create a low-carbon economy. If the economy stops growing now and we continue with existing technologies, the current level of annual global emissions of close to 50 billion metric tons of carbon-dioxide-equivalent would imply atmospheric concentrations of close to 700 parts per million within a century, and entail huge risks.

The challenge is to break the link between economic output and emissions. If we can (and indeed we can and must), then growth could continue for another few decades. That does not mean indefinitely: as Woody Allen reputedly once said, “Eternity is really long, especially near the end.” But a few decades of economic growth, with accompanying policies focused on development, particularly among the poorest groups—for the six billion people who live in poor countries (compared with one billion who live in rich countries)—would allow, in large measure, the battle against world poverty to be won.

Both the advocates of Limits to Growth and those who say that low-carbon growth is too costly, and that we can continue with high-carbon growth, make the same mistake. They embrace a view embodying “limited substitutability” and “restricted scope for investment in changing technologies”: they embrace the growth theories of the mid-twentieth century. What we need now are the growth theories of the late-twentieth and early-twenty-first centuries that show that we can invest in discovering and deploying new technologies, that such deployment itself will have strong effects on saving energy, and that technological output and the natural environment are closely bound together and mutually dependent.

We also need practical demonstrations of what is possible, which will be fundamental to generating change. For example, the capital cost of solar electricity is swiftly becoming lower, and high-voltage DC grids are drastically reducing the costs of electricity transmission. Renewable energy from dispersed areas (with different variability of sun and wind) can therefore be transmitted over long distances. With zero-carbon electricity we can have zero-carbon surface transport. And technical progress is moving rapidly—we will find many more such developments along the way. The power of examples is crucial and we must look particularly to rich countries, with their greater wealth and technologies, to offer them.

We have already embarked on what will be the most dynamic and creative energy and industrial revolution in our economic history: the transition to low-carbon growth. And this growth will be more energy-secure, safer, quieter, cleaner, and more biologically diverse. High-carbon growth would kill itself: first from the high prices of hydrocarbons that could result, and second, and more fundamentally, from the very hostile physical environment it would create.

There is no doubting McKibben’s sincerity and his ability to communicate the magnitude of the risks we face. But his dire prognosis is too pessimistic in relation to the recent advances domestically and internationally in avoiding even bigger changes to the climate by reducing greenhouse gas emissions. Although the United Nations climate change conference in Copenhagen last December was disappointing in many ways, it could have been much worse. The Copenhagen Accord put forward by Brazil, China, India, South Africa, and the US has provided a basis for discussions about an international treaty. It has its fragilities, and the process of building agreement will not be easy, but substantial progress has been made in the first months of 2010.

The accord recognizes that climate policies should seek to limit the rise in global average temperature to no more than 2˚C above preindustrial levels. An analysis by my colleagues at the Grantham Research Institute on Climate Change and the Environment at the London School of Economics showed that in order to have a reasonable, or 50 percent, chance of reaching the 2˚C goal, global annual emissions of greenhouse gases should be reduced from about 47 billion metric tons of carbon-dioxide-equivalent today to about 44 billion metric tons in 2020, to much less than 35 billion metric tons in 2030, and to much less than 20 billion metric tons in 2050.

So far, more than one hundred developed and developing countries have associated themselves with the Copenhagen Accord, and seventy-five countries, which are collectively responsible for more than 80 percent of current annual global emissions of greenhouse gases, have submitted targets and intended actions that are now listed in the appendices of the accord.

If countries deliver their “high intention” reductions, the plans submitted to the Copenhagen Accord would result in global annual emissions of about 48 billion metric tons of carbon-dioxide-equivalent in 2020. While this would imply that emissions would peak before 2020, it would nevertheless fall short of a “climate responsible” target of 44 billion metric tons. Annual emissions of 48 billion metric tons could still, at a stretch, be consistent with a 2˚C goal, although they would involve more difficult and costly annual reductions of emissions during the decades after 2020. The actions that are proposed between now and 2020 in the appendices of the accord represent a reduction of 7–8 billion metric tons compared with an estimated level of emissions of 55–56 billion metric tons under “business as usual.” Thus, the planned actions would take us two thirds of the way from about 56 to 44 billion metric tons.

While we are making a start, it is only a modest one and there does not, as yet, seem to be sufficient recognition of the magnitude of the challenge of adjustment and the risks of delay. The world must emit an average of no more than four metric tons per capita of carbon-dioxide-equivalent by 2030, and about two metric tons per capita by 2050. The current average is about seven tons per capita, with the United States averaging more than twenty metric tons, Europe ten to twelve metric tons, China about six metric tons, India less than two metric tons, and much of sub-Saharan Africa less than one metric ton per capita. At the same time, we must recognize not only that change is possible but that the transition will be dynamic and creative with innovation that will drive growth. The goal of the low-carbon economy is very attractive as a way of consuming and producing. McKibben’s book will surely help to improve that understanding among the people of the United States.

When world leaders and their negotiating teams left Copenhagen last December, it was unclear how solid a platform the accord would create. That the major emitters would submit action plans by January 31 was not assured; but it has happened. Further, as indicated in the accord, a High-Level Advisory Group on Climate Change Financing has been established by the secretary-general of the United Nations, under the co-chairmanship of the prime ministers of Ethiopia and the UK, and it has begun its work. The advisory group is to suggest options for generating, by 2020, $100 billion per year, including both public and private resources, that will flow from developed to developing countries in order to support both adaptations to lower emissions and mitigation of the effects of achieving them.

Progress is being made on the structure of action for preserving and planting forests, with a constructive meeting in March led by France and Norway and with extensive participation by many other countries, including the rainforest nations. Overall, some of the building blocks for a sensible political agreement are being put in place for the next meeting of the parties to the United Nations Framework Convention on Climate Change in Cancún at the end of this year.

Before constructive negotiations can take place, the world requires that carefully assessed options be put forward to deal with the key elements of any agreement. In the cases of finance and forestry, that analysis and assessment is taking place in ways that are international and that might be trusted by the world community. Corresponding mechanisms are urgently required for developing and sharing technology and for the objective measurement of emissions by countries. If processes for the assessment of options for dealing with these two issues could be put in place quickly, then the world will have prepared itself for sound and fruitful discussions at Cancún. In the absence of such basic preparations, negotiation by international bureaucrats on issues that require technical underpinnings and the evaluation of complex policies risk being unproductive, misguided, and chaotic. But if the foundations are laid, then countries across the world can go forward with some confidence that constructive responses to the two biggest challenges of our century, overcoming poverty and managing climate change, can be found.

McKibben’s engaging and persuasive book will add greatly to the sense of urgency. It will add realism to the case for strong adaptation to the changes that our past and current actions are bringing to our natural world. But it risks undermining confidence that we can find a way forward. That is not McKibben’s intention, as he makes absolutely explicit. Nevertheless, he is too pessimistic about the ability of the world to respond. Such pessimism can be self-fulfilling. Sound analysis, educated imagination, strong leadership, and a collaborative spirit can radically reduce the immense risks we are facing. And they could chart the way to three or four decades of great innovation and creativity, and lay the foundations for a more sustainable, collaborative, and equitable world.

—May 26, 2010

This Issue

June 24, 2010