Emails (excerpted), Naomi Oreskes, professor of history, the University of California, San Diego, April 18-19, 2013

7:31 pm

April 18, 2013

It is amazing to me that in 2013 any person could say such a thing with a straight face.  The scientific consensus has been affirmed and re-affirmed many times, most obviously by the IPCC in the Fourth Assessment Report, which stated that warming was "unequivocal. " The report also has over 1000 pages dedicated to explaining adverse impacts, which clearly demonstrate that this is indeed a problem. These adverse impacts include sea level rise, increased extreme weather events such as heat waves, droughts, floods, and heavy precipitation events, changes in the distribution of species, loss of Arctic sea ice and permafrost (with adverse impacts on, among other things, oil drilling in the Alaskan tundra!).

Many people have tried to discredit the IPCC, but its results have been repeatedly re-affirmed across the globe by the world's oldest and most respected scientific organizations, including the U.S. National Academy of Sciences, the U.K. Royal Society, and virtually every major scientific society in the United States.   A study published in 2012 in the Proceedings of the National Academy of Sciences demonstrated that 97-98% of all climate researchers agree with the conclusions of the IPCC that man-made warming is underway, and having adverse impacts.

http://www.pnas.org/content/107/27/12107.short

The conclusion that humans have contributed to global warming cannot be separated from the role  of greenhouse gases  produced by burning fossil fuels.  To separate human activities from greenhouse gases is  a false dictotomy.  Increased greenhouse gases are a direct result of human activities, mainly burning fossil fuels.  The scientific conclusion is that "most" of the observed warming of the past fifty years is very likely to be due to the increase in greenhouse gas concentrations, caused by burning fossil fuels. Most of the rest has been caused by deforestation.  Both are human activities, and both are a problem, because they drive adverse impacts like heat waves and droughts.        

By "very likely" the IPCC means, specifically, 90-100% certain.

One might note that Texans, with their historian of suffering from both heat waves and droughts, as well as vulnerability to hurricanes and sea level rise along the Gulf Coast, should be particularly worried about these issues.

I recently updated a paper of mine, first published in 2007, for a second edition that will be published later this year.  I wrote this paper in response to questions like the ones you are asking here.  You are welcome to read it and cite it.  There is a discussion in it of additional work on the consensus question done since my 2004 paper.  The original version was published as :

Oreskes, Naomi, 2007, “The scientific consensus on climate change: How do we know we’re not wrong?” Climate Change: What It Means for Us, Our Children, and Our Grandchildren, edited by Joseph F. C. DiMento and Pamela Doughman, MIT Press, pp. 65-99.

Naomi Oreskes

4:31 pm

April 19, 2013

Of course the word "problem" is subjective, but insofar as one can say that there is evidence that bears on the issue, the scientific community has amply supplied that evidence.

Naomi

On 4/18/13 4:05 PM, Selby, Gardner (CMG-Austin) wrote:

Good afternoon.

I write because we are checking a claim by a Texas legislator, Wayne Smith, who said this week: "Science has not shown greenhouse gases to be a problem.”

I am aware of your article in Science in December 2004. Have you followed up on it? Has the described consensus changed?

Your paper is clear there was/is a consensus that human activities have contributed to global warming. Do you also conclude that there is consensus that greenhouse gases are a problem? Are there particular, recent works that bear on this?

Thank you for any and all assistance.

 

wgs

W. Gardner Selby

Editor

PolitiFact Texas