In November 2009, e-mails and other documents, such as draft papers and climate data, were hacked from the East Anglia Climate Research Unit. The resulting controversy undermined public trust in the integrity of climate science. Moreover, in early 2010, several errors were found in the 2007 IPCC report. This did not help restore public trust in climate science either.

Since then, independent reviews have vindicated the East Anglia researchers and a high-powered review committee is working to improve the IPCC peer-review process. But in Virginia, Attorney General Ken Cuccinelli is investigating a former University of Virginia climate scientist, Professor Michael Mann, under the Virginia Fraud Against Taxpayers Act. Even self-declared climate skeptics have criticized Mr. Cuccinelli’s decision.

Inspired by these events, 255 members of the US National Academy of Sciences, including 11 Nobel Prize winners, published an open letter in Science. The letter condemns, in strong words, the assault on climate science, saying that “[m]any recent assaults on climate science and, more disturbingly, on climate scientists by climate change deniers, are typically driven by special interests or dogma, not by an honest effort to provide an alternative theory that credibly satisfies the evidence.” The signatories explain what climate science is, reiterate that the current evidence for climate change is compelling, and call for immediate action to reduce greenhouse gas emissions.

Although the letter does a good job at explaining how climate science works and what would constitute a real challenge to the prevailing scientific consensus on climate change, I thought it might be useful to also address this issue in this blog.

As a disclaimer, I should remind the reader that I am social scientist, not a natural scientist, by profession. While the basic principles that govern the social sciences are similar to those that govern the natural sciences, there are undoubtedly practical differences.

Nonetheless, here are my two cents.

1) Science is a collective enterprise. In this regard, climate science is not any different from other sciences: the core idea of anthropogenic global warming is based on a large number of independent studies. Some are more important than others, but the prevailining consensus does not depend on any single study.

2) In science, a theory is challenged by accumulating evidence that is not consistent with it. Reading scientists’ private e-mails may shed some light on how careful and neutral they are. But the content does not challenge a scientific theory, unless there is direct evidence of systematic misconduct. On this point, I dare the reader to go through his or her own e-mail correspondence. I am the first to confess that some of my professional correspondence might not leave a favorable impression if publicized. Scientists are human beings, and they (we) treat private correspondence as… private correspondence. It is the public output, namely refereed publications, that should be fully transparent and ruthlessly criticized by other scientists.

3) A core feature of science is self-correction. Scientists are trained to find anomalies in existing studies and develop theories that can address those anomalies better than the received theories. The system is not perfect, and even incorrect theories may survive for extended periods of time, but I am not aware of any superior system.

4) Climate change is a particularly difficult issue because one of the key implications of the prevailing consensus is that steep emissions reductions are warranted unless societies are willing to accept rapid global warming with potentially disastrous consequences. This urgency, combined with the immense complexity of the Earth’s climate system, implies that any public policies are inevitably based on uncertain conclusions. The fact that we are not sure how much temperatures will increase, and to what effect, will not go away anytime soon. Our political systems must find a way to deal with it.

It is clear that climate change puts scientists under extreme pressure, creating perverse incentives to either overstate the certainty of scientific findings or refrain from publicizing “inconvenient truths,” depending on how the society responds to troubling findings and calls for urgent action. My own view is that climate scientists deserve much more credit for their efforts than they get. There is nothing wrong with challenging prevailing theories — there is nothing more important in science — but persecuting individual scientists for doing their job should be unacceptable in every democratic and free country.