To the editor:

Daniel Murphy’s recent letter in your paper (Nov. 24) is a thoughtless regurgitation of standard denialist talking points that don’t stand up to the slightest bit of scrutiny.

His screed includes false claims about: 1. The Great Barrier Reef (it is, in fact, gravely threatened by climate change and ocean acidification); 2. polar bears (they too are threatened despite claims by climate change deniers to the contrary, whom Murphy cites and who definitively have been refuted in the peer-reviewed scientific literature; and 3. The warming of the planet (it has warmed roughly 2 degrees Fahrenheit since the dawn of the industrial revolution, and all of the warming has been attributed to human-caused greenhouse gas increases from fossil fuel burning and other human activities).

Murphy makes untruthful statements about my own research in the late 1990s that resulted in the well-known “hockey stick” curve, which demonstrates recent warming to be unprecedented over the past thousand years.

He parrots discredited criticisms by two individuals (Stephen McIntyre and Ross McKitrick) with no expertise in climate science and fossil fuel industry ties.

As I recount in “The Hockey Stick and the Climate Wars,” the “hockey stick” has been ceaselessly attacked by climate deniers and by individuals like Murphy who parrot their talking points owing to the simple, undeniable message it conveys about the dramatic impact of human activity on our climate.

Murphy seems willfully ignorant of the fact that the scientific community has overwhelmingly validated our findings.

The highest scientific body in the U.S., the National Academy of Sciences, affirmed our findings in an exhaustive independent review published in June 2006 (see "Science panel backs study on warming climate,” New York Times, June 22, 2006).

In the two decades that have passed since our original work, dozens of groups of scientists have independently reproduced, confirmed and extended our findings, including an international team of nearly 80 scientists from around the world, publishing in the premier journal Nature Geoscience in 2012. They concluded that recent warming is unprecedented over an even longer time frame.

The most recent report of the Intergovernmental Panel on Climate Change concluded that recent warmth is likely unprecedented for at least the past 1,300 years, and there is now tentative evidence that the recent warming spike is unprecedented in tens of thousands of years.

Readers who are genuinely interested in the truth behind the science, rather than the falsehoods and smears perpetuated by individuals like Murphy, should read scientist-run websites like and and books like my “Dire Predictions: Understanding Climate Change.”

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

Michael E. Mann

Distinguished Professor, Department of Meteorology and Atmospheric Science

Penn State University

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