Since the Environmental Protection Agency determined in December 2009 that climate change is a threat to the planet and human health—and was being driven by human activity—the agency has received 10 petitions challenging its findings. On July 29, 2010, the EPA denied those petitions. In general, petitioners argued with the EPA's "Endangerment Finding," their arguments drawn largely (according to related documents) from "disclosed private communications among various scientists, a limited number of errors and claimed errors in the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report…and submissions of a limited number of additional studies not previously considered as part of the scientific record of the Endangerment Finding."
None of these were substantial enough to outweigh the decades of evidence the EPA has amassed clearly indicating that: greenhouses gases have risen to unprecedented levels; the accumulation of these gases is warming the planet; climate change is visible through shrinking Arctic ice, rising oceans and rising temperatures; the rate of climate change is increasing, and greenhouse gases are driving this increase; and that risks to public health and welfare as a result of climate change continue to increase, too.
In 2009, select leaked e-mails from the Hadley Climatic Research Unit (CRU) at Britain's University of East Anglia appeared to vindicate climate change skeptics by suggesting scientists were deleting information that contradicted climate change. But upon further scrutiny, the EPA found that these e-mails were taken out of context, and do not, when in context, reveal any sort of fraud or misconduct. Climate change is not only overwhelmingly evident, the EPA found, it poses a serious threat. For the EPA to consider petitioners" arguments, it wrote, it would have to "ignore the deep body of science that has been built up over several decades and the direction it points in, and to do so based not on a careful and comprehensive analysis of the science, but instead on what amount to assertions and leaps in logic, unsupported by a rigorous examination of the science itself."