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Is climate change science “real science”? Can climate change experts give expert evidence in court?

Canadian courts have not yet wrestled with this issue, but American courts have. The leading case is Green Mountain Chrysler v. Crombie. In 2007, the auto industry tried to prevent leading climate change experts from giving expert evidence, on the ground that their work was not reliable science, and did not meet Daubert criteria (the legal test used to keep junk science from cluttering up courtrooms). The case involved an auto industry lawsuit to block Vermont from following California limits on GHG emissions from automobiles. Judge Sessions ruled that Dr. James Hansen, Dr. Barrett Rock and Mr. K.G. Duleep could offer reliable expert evidence about greenhouse gas emissions and climate change.  About Dr. Hansen, for example, he ruled:

Hansen’s testimony provides the Court with important information on the nature and risks of global warming. As the regulation at issue was crafted in response to a recognition of these risks, understanding the nature of the regulation and its effects depends on an understanding of the science that underlies global warming. By explaining how such warming begins and grows, as well as how it may be addressed at this point in time, Hansen illuminated important background to the issues in this case. While Hansen does not, as noted above, argue that the regulation will in itself solve the global warming problem, his testimony provided valuable context for the Court’s consideration of the Plaintiff’s contentions that the regulation is essentially useless. Therefore, the Court finds that Hansen’s opinions do assist the Court, as the trier of fact in this case.

Based on the evidence of these three experts, Judge Sessions upheld Vermont’s decision to adopt California limits on greenhouse gas emissions from automobiles. In turn, this helped pave the way for this year’s historic compromise, in which what is left of the American auto industry agreed to support major improvements in automobile fuel efficiency.

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