Penn State professor refutes Heiberg's climate change letter

An individual named Rick Heiberg did a tremendous disservice to your readership in his letter about the topic of human-caused climate change and about my scientific work specifically in his recent letter (“Climate change: settled science?”, 3/18/16).

It is difficult to find a single true statement in his inflammatory, uninformed polemic. Take for example his assertion that the reality of human-caused climate change is “[sic] far-from ‘settled’ in the actual community of climate scientists.” The truth is just the opposite. The more than 30 science organizations that have weighed in on the matter of climate change have concluded that climate change is real and human-caused. So have the U.S. National Academy of Sciences, the national academies of all other industrial nations, and 97 percent of all scientists who have published on the matter.

Mr. Heiberg also levels false allegations about the well-known “hockey stick” temperature curve. Published a decade and a half ago, the hockey stick temperature reconstruction demonstrates that recent warming is unusual over at least the past 1,000 years. As I recount in “The Hockey Stick and the Climate Wars”, our work has been attacked by industry-funded climate change deniers for more than a decade owing to the simple, undeniable message it conveys about the dramatic impact human activity is having on Earth’s climate. Mr. Heiberg cites these bad faith attacks in an attempt to mislead readers into thinking that our work has been ‘discredited.’

He conveniently fails to note that the highest scientific body in the U.S., the National Academy of Sciences, affirmed my research findings in an exhaustive independent review published in June 2006 (see e.g. “Science Panel Backs Study on Warming Climate”, New York Times, June 22, 2006).

In the decade and a half since our original published work, dozens of groups of scientists have independently reproduced, confirmed, and extended our findings, including most recently an international team of nearly 80 scientists from around the world, publishing in the premier journal Nature Geoscience. The most recent report of the Intergovernmental Panel on Climate Change, the most authoritative assessment of climate science available, concluded that recent warmth is likely unprecedented over an even longer timeframe than we had concluded (at least the past 1,400 years). Of course, the “hockey stick” is only one of numerous independent lines of evidence that have led the world’s scientists to conclude that climate change is (a) real, (b) caused by the burning of fossil fuels, and (c) a grave threat if we do nothing about it.

Readers interested in the truth behind the science should consult scientist-run websites like skepticalscience.com, or books on the topic like my own “Dire Predictions: Understanding Climate Change.” Let’s get past the fake debate about whether the problem exists, and on to the worthy debate about what to do about it.

Michael E. Mann is a distinguished professor with the Department of Meteorology at Penn State University. He is director of the Penn State Earth System Science Center.