By Michael Mann

Paul deWitt’s recent commentary in your paper (“The danger is the wrongheaded efforts to fight climate change,” The Bulletin, Oct. 20) subjected readers to falsehoods about the science of climate change and untruthful assertions about me specifically.

His execrable screed reads like a game of climate change denial bingo, hitting all of the usual denialist talking points. DeWitt begins by (1) doubting “whether climate change is caused by man-made carbon emissions.” The world’s scientists, including the U.S. National Academy of Sciences (founded by Republican President Abraham Lincoln in the 19th century) has concluded that “most of the recent change is almost certainly due to emissions of greenhouse gases caused by human activities.”

Then we get the shopworn claim that (2) it is Al Gore alone (a must-mention boogeyman in any denialist diatribe) who “posits the dangers the world faces if we don’t reduce our carbon emissions.” Gore, it seems, is behind the unprecedented droughts, wildfires, floods and superstorms that have led our national security community to conclude that climate change constitutes the greatest security threat we face in the years ahead. National security experts see climate change as a “threat multiplier” that takes existing tensions (like the drought in Syria that led to conflict in the region and the emergence of ISIS) and amplifies them.

Next, we get the absurd claim that (3) climate “models” alone provide evidence that “anthropogenic climate change is occurring.” Actually, there are dozens of independent lines of evidence, from the basic physics of the greenhouse effect, to the irrefutable evidence that we are increasing the levels of greenhouse gases in the atmosphere, to the fact that unprecedented warming is occurring with widespread impacts, that has led the world’s scientific community to conclude that climate change is real and human-caused.

For good measure, we also get the favorite denialist claim that (4) CO2 is “a major gas of life” and can’t possibly be dangerous at such low levels! Cyanide and arsenic are both fatal to human beings in much lower concentrations than the level (400+ ppm) of CO2 in our atmosphere, a level that Earth incidentally hasn’t seen in several million years.

And the list goes on, one discredited climate denial myth after another. And rather than listening to the overwhelming consensus of the world’s scientists, deWitt prefers that we instead listen to a single climate change contrarian named Gordon J. Fulks. Fulks has no scientific credentials in climate science and instead serves as a paid speaker for the “Cascade Policy Institute,” a right-wing front group for polluters and dark money interests.

DeWitt even manages to level an untruthful attack against me and my work reconstructing temperature changes over the past 1,000 years, which resulted in the well-known “hockey stick” curve. This curve demonstrates the unprecedented nature of recent warming over the past millennium. It has been attacked by climate change deniers like deWitt owing to the simple, undeniable message it conveys about the dramatic impact human activity is having on Earth’s climate.

Conveniently, deWitt fails to acknowledge the fact that the scientific community has overwhelmingly validated our findings. The highest scientific body in the United States, 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). The most recent report of the Intergovernmental Panel on Climate Change concluded that recent warmth is likely unprecedented over an even longer time frame (at least the past 1,300 years).

Readers interested in the truth behind the science, rather than the falsehoods and smears perpetuated by individuals like deWitt should consult scientist-run websites like skepti calscience.com or books on the topic like my own “Dire Predictions: Understanding Climate Change.”

Let’s get past the fake debate about whether climate change is real and on to the worthy debate over what to do about it.

— Michael E. Mann is a professor in the Department of Meteorology and Atmospheric Science at Penn State University.

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