THE battle to get the US government to accept the evidence of its own scientific advisers on how greenhouse gas emissions are warming the planet has reached the highest court in the land. Last week, a case brought by Massachusetts, other states and environmental groups against the US Environmental Protection Agency, claiming the EPA has failed to regulate pollutants that cause global warming, came before the Supreme Court.
A decision is not likely until towards June next year, but whatever the verdict, it will shine a spotlight on an issue that Washington has mostly ignored. It is also likely to make all the more apparent the need for Congress to take action to limit emissions of greenhouse gases.
As one of the climate scientists who helped write an advisory brief for the court for this case, I hope the court will weigh in on the side of Massachusetts, for two reasons. First, it would discourage government agencies from distorting science, as the EPA has done here. Second, it would give the agency an opportunity to go back and do its job properly. It would allow it to look at the scientific evidence and evaluate objectively whether 鈥� in the words of the section of the clean air act at issue here 鈥� greenhouse gas emissions 鈥渕ay reasonably be anticipated to endanger public health or welfare鈥�.
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The case dates back to 2003, when the EPA denied a petition by some US states and other groups that it regulate greenhouse gases from cars and other mobile sources. The agency cited a 2001 report by the National Academy of Sciences (NAS), requested by the Bush administration, that it said showed scientific knowledge was still too uncertain to support limits on greenhouse gases. Our brief to the court 鈥� to which many of the world鈥檚 leading experts on climate, including a majority of the authors of that NAS report, contributed 鈥� argues that the agency has misrepresented the report, making the science of climate change appear more uncertain than it is.
In its denial, the EPA did accurately summarise some of the evidence in the NAS report, including the observations that atmospheric concentrations of greenhouse gases were increasing due to human activities, that global temperatures were rising and that this rise was large compared to natural variability. However, it left out the academy鈥檚 summary of what is perhaps the past decade鈥檚 key scientific finding in climate change, and the most compelling reason why regulation might be needed: that the rise in concentrations of gases and the rise in temperatures are causally linked. As we wrote in our brief to the court, this is a fundamental omission, akin to leaving out gravity from a summary of Isaac Newton鈥檚 theory of how apples fall to Earth and planets move in the heavens.
Although the science by itself prescribes no particular policy, the law requires the EPA to ask a specific question, which it has not asked: does the scientific evidence on climate change show that greenhouse emissions 鈥渕ay reasonably be anticipated to endanger public health or welfare鈥� and thus according to the clean air act make the case for regulatory action?
This legal principle is a powerful and important means of protecting against complex environmental harms. It does not require a scientific conclusion that greenhouse gases will endanger welfare, only that it is reasonable to think that they may. It is this precautionary principle that in the 1970s allowed a more proactive EPA to start protecting Americans from the toxic consequences of lead additives in gasoline even before the scientific details of lead in the environment were fully understood. Americans are fortunate that the act permitted early action because, as it turned out, leaded gasoline had a far bigger effect on lead levels in blood than had originally been thought. The early removal of lead from gasoline in the US saved billions of dollars and protected the health of tens of millions of people.
In the case of climate change, the science has long passed the point where the law鈥檚 precautionary standard for action is met. Indeed, in many ways, the science of how greenhouse gas emissions cause climate change is clearer now than the science of how leaded gasoline affected blood lead levels was in the mid-1970s. Even though much more research has to be done and many uncertainties remain, especially on how climate will change in specific regions, the pervasive evidence supporting the basic theory is so compelling that it has crystallised a remarkable consensus within the scientific community.
Within government agencies, regulatory decisions that encompass the future of the planet should be based on a clear-eyed evaluation of the best science available, applied according to the standards prescribed by law. The Supreme Court is in a position to apply this to the EPA. For all our sakes, we hope that it does.
鈥淒ecisions that encompass the future of the planet should be based on the best science available鈥�
Scott Saleska is in the department of ecology and evolutionary biology at the University of Arizona, Tuscon. The brief to the court, along with the list of co-authors, can be found (PDF file)
