A world in which all human beings were equal, rational, and perfectly governed, when confronted with the prospect of global warming, might reach an optimal decision based on compelling climate science. That ideal world would then find effective international agreements to restrict greenhouse gas emissions and avoid harmful climate change.
We do not live in such a world. In reality, the science of climate change, no matter how advanced, will never be sufficient to tell humanity what to do. Science may be able to inform policy by forecasting how severe climate change will be, given different greenhouse gas levels. However, experience teaches that science alone is never enough. When confronting environmental challenges, considerations of fairness, equity, and justice must also inform any successful international agreement.
This is certainly true of three major ethical dilemmas now complicating the climate change debate: how to balance the rights and responsibilities of the developed and developing world; how to evaluate geo-engineering schemes designed to reverse or slow climate change; and how to assess our responsibility to future generations who must live with a climate we are shaping today.
The 1987 Montreal Protocol on Substances that Deplete the Ozone Layer, together with subsequent agreements, is often hailed as a model environmental treaty. Although replacing chlorofluorocarbons (CFCs) clearly is much easier than weaning the world off fossil fuels, the ethical dimension of the ozone treaty holds lessons for tackling global warming. In dealing with CFCs, governments, industry, and science — realizing that CFCs and related manmade chemicals caused ozone depletion — quickly developed ozone-safe substitutes. And recognizing that developed and developing countries had differing legitimate concerns, the international ozone agreements called for developed countries to take the lead in addressing the issue, because these nations had produced most of the substances implicated in destroying stratospheric ozone. A fund was established to help developing countries phase out ozone-destroying chemicals. Technology transfer was addressed.
Many different segments of society now recognize that an effective climate agreement must also have such an ethical dimension. Religious organizations have contributed to the dialogue, addressing such fundamental questions as the rights of poor people and developing nations. “Action to mitigate global climate change,” the United States Conference of Catholic Bishops has declared in a statement, “must be built upon a foundation of social and economic justice that does not put the poor at greater risk or place disproportionate and unfair burdens on developing nations.”
Nearly all the nations of the world now agree that atmospheric greenhouse gases should be kept below a level that would produce dangerous human-caused climate change. However, exactly what level is “dangerous”?
The Intergovernmental Panel on Climate Change (IPCC) is required by its mandate to be policy-neutral. As one of the authors of its 2007 Fourth Assessment Report, I can testify that IPCC scrupulously avoided all forms of policy advocacy. Its task was simply to assess the scientific research literature in a way that was policy-relevant but not policy-prescriptive.
In any case, dangerous climate change is a subjective concept, depending on one’s values and risk tolerance, among other factors. Science cannot say that a given atmospheric level of greenhouse gases is safe, and another slightly higher one is not. Expecting that degree of precision from climate science is as unrealistic as expecting medical science to declare that one level of cholesterol is surely tolerable, and any higher level is certain to lead to a heart attack. Climate is complex. Einstein once remarked that everything should be made as simple as possible, but not more simple than that.
However, science, speaking through the IPCC, can provide guidance by suggesting what degree of severity of climate change is likely to be associated with any specific amount of greenhouse gases in the atmosphere. This information is found in great detail in the IPCC reports. Mainstream climate scientists like me regard these reports as the gold standard in our field. We use IPCC reports as textbooks for our graduate students, and they have been recognized as authoritative by national academies of science, by scientific professional societies, and most recently by the award of the 2007 Nobel Peace Prize. The IPCC reports have guided the European Union in formally adopting a specific goal of holding global warming to no more than 2 degrees Celsius (3.6 degrees Fahrenheit) above the average pre-industrial temperature of the mid-19th century.
In December 2007, at a major United Nations-sponsored climate conference in Bali, I joined other climate scientists to help publicize a statement signed by more than 200 climate scientists from more than 20 countries. Many of these scientists were also IPCC authors, but all of us signed the statement strictly as individuals. Our statement declared that by 2050 global greenhouse gas emissions should be cut by at least 50 percent below 1990 levels. The goal, we scientists said, should be to stabilize greenhouse gas concentrations at a CO2-equivalent level well below 450 parts per million.
Not surprisingly, the Bali negotiators failed to reach an agreement in which nations accepted binding commitments with firm timetables and quantitative targets for greenhouse gas reductions. The problem was not that the science was unreliable or that the negotiators were incompetent. The major obstacle was that nations, like individuals, do not take major decisions solely on the basis of scientific results. This realization may seem obvious, but we scientists are often politically naïve.
It is now increasingly clear that meaningful international action to limit climate change not only requires compelling scientific evidence and recognition of legitimate national interests, but also must focus on considerations of equity and ethics. The climate system is a global commons. Yet the consequences and costs of climate change do not fall equally on all nations and all parts of the globe. And with fossil fuels now supplying 80 percent of global energy, and thus enabling much of modern economic progress, nations will accept constraints on their freedom to emit greenhouse gases only when they are satisfied they are being treated fairly as part of a global response.
The differing perspectives of developed and developing nations — and the contrast between past and future actions — remain a key issue. Today, more than one out of every four molecules of carbon dioxide in the atmosphere has been put there by human actions, chiefly burning coal, oil, and natural gas. If we ask which nations are responsible for this dramatic increase in greenhouse gases, the answer is obvious — the developed nations. The United States, currently with about 5 percent of global population, has produced about a quarter of all the carbon dioxide that humankind has added to the atmosphere.
On the other hand, if we ask where the future growth in carbon dioxide emissions will originate, the answer is that the developing nations will largely be responsible. The developing nations with large populations — China foremost, followed by India, Brazil, Russia and others — are rapidly exploiting fossil fuels to power economic development. China, which now builds a new large coal-fired power plant every week or so, has already passed the United States as the nation that emits the most carbon dioxide. Is this fair? Ethical concerns demand a principled understanding of the differing rights and obligations of both developed and developing countries.
The sobering prospect of using geo-engineering to counter human-caused climate change also raises profound ethical issues. Many geo-engineering approaches are conceivable. For example, it is relatively easy to propose ways to make the Earth more reflective, in the hope that reduced absorption of sunlight might compensate for a strengthened greenhouse effect. Large mirrors might be placed in space. Sulfate particles or their chemical predecessors might be launched into the stratosphere. As the consequences of human-caused climate change become more severe and apparent, the temptation to seek a relatively simple technological remedy will surely increase.
I believe this temptation should be resisted. At best, if it worked well, geo-engineering would be addictive, committing future generations to continue it and encouraging further reliance on fossil fuels. More probably, geo-engineering would create additional problems while exacerbating existing ones. Artificially increasing the Earth’s reflectivity, for example, does nothing about the ongoing acidification of the oceans resulting from carbon dioxide being added to the atmosphere.
Research is far preferable to ignorance, and I feel about geo-engineering exactly as I do about nuclear war: Study it, by all means, but never try it. It would be highly irresponsible to conduct a massive international intervention on our planet without being virtually certain there would be no side effects making the cure worse than the disease. Such certainty is highly unlikely. Even relatively simple, small-scale plans can go wrong. If geo-engineering is the last resort in a worst-case scenario, let us do all we can to avoid that scenario. Who has the moral — and legal — right, on behalf of all nations, to tinker with the entire global environment?
Finally, the issue of intergenerational equity requires agreement on how decisions taken now may affect people not yet born. The climate system has several built-in delaying mechanisms. The consequences of a heightened greenhouse effect appear after a time lag, often decades or more. Oceans, as well as ice and snow, react slowly to the increasing burden of greenhouse gases. We have already committed our descendants to many centuries of sea-level rise. We benefit now from using cheap and abundant fossil fuels, and we use the atmosphere as a free dump for the waste products. In doing so, however, we sentence our children and grandchildren to cope with the resulting climate change.
I am convinced that a scientific community that aspires to be helpful to society must include ethics and equity as an integral part of its research agenda. We should place greater emphasis on providing quantitative information relevant to the ethical consequences of different policy options. For example, policymakers urgently need to know how climate change will affect different regions of the world and different economic sectors. The coming temperature change labeled “global warming” is simply a symptom of climate disruption. Research is required to generate specific forecasts of effects on water supply, on hurricanes and other storms, and on droughts, floods, and many other phenomena. Consequences for ecosystems and biodiversity worldwide are among the unknowns. Options and costs of adaptation to climate change will vary greatly around the globe and among developed and developing nations, and science has much to contribute to understanding these factors.
Incorporating such considerations into international negotiations on climate change is not fanciful or unrealistic. Indeed, experience in other domains teaches us that an ethical basis is essential in order to reach effective solutions. The historical development of the Montreal Protocol and follow-on agreements to deal with human-caused damage to stratospheric ozone illustrates clearly the benefits of taking ethics into account.
Let us recognize the damage we have already done to the climate system and resolve to minimize the additional damage we threaten to cause in the future. That is our moral and ethical responsibility to our neighbors on this small planet, to our descendants, and to all life on Earth.