The Third National Climate Assessment is out, fully available to the public, and gives the most detailed picture yet of how global warming is affecting the United States. It was an exhausting effort over more than three years by hundreds of scientists. I had the privilege of being one of the authors, and I am proud of the work we did. And as a member of the 44-member advisory panel, which approved each and every chapter of the report by consensus, I believe our description of the evidence of a changing climate across the country can be an important resource for citizens and policy makers alike.
US Trends in Heavy Precipitation (from the National Climate Assessment 2014)
Of course, upon release of the report it’s not surprising that it would receive criticism. Unfortunately, much of that criticism was partisan and most referred to the report as the President’s. In fact it was the product of a long process with multiple layers of peer review, as I described in an earlier post. The product is ultimately a government report because that is the end of the process set by the Act of Congress that called for the report. Similarly, some critics complained that the report didn’t evaluate the climate policies of the Obama Administration, but again the statute calls for an assessment of impacts, not an evaluation or recommendations on policy.
The statement from the Chairman of the House Committee on Science, Space and Technology is the most puzzling. Chairman Lamar Smith wrote that the report “includes unscientific characterizations on the connection between severe weather events and climate change and fails to explain the absence of warming over the last 15 years.” Neither is true. Both issues are addressed in the report directly in the chapters and in the Frequently Asked Questions (FAQ) in the appendix.
The supposed “absence of warming over the last 15 years” is just a misstatement, repeated over and over by those who apparently wish to discredit the preponderance of scientific evidence of a changing climate. There has been no absence of warming, though as the report clearly notes, the rate of warming changes through time. To really look at the evidence for climate change, particularly in a single measure such as air temperature, one needs to look over a longer period. In the last 15 years there has been substantial increased heat content in the ocean along with increases in atmospheric temperature. As noted in the report, the most recent decade was the warmest since record-keeping began in the 19th century.
Chairman Smith states, without any substantiation, that “there is little science to support any connection between climate change and more frequent or extreme storms.” In reality, there is clear evidence of the connections documented in the report. The frequency of more extreme temperatures, both warm and cold, has changed. And increased frequency of heavy rainfall events in particular areas, and changes in hurricane intensity and rainfall, have all been linked to climate change from model predictions validated through observations. This is clearly documented in the report, which says there was “a substantial increase in most measures of Atlantic hurricane activity since the early 1980s, the period during which high quality satellite data are available.” The data is shown in the report, though Chairman Smith incorrectly asserts the opposite. It is true, as the report notes, that some much smaller scale events such as tornadoes and thunderstorms cannot currently be related to the changing climate because there are too many other driving factors at those scales. That is a far cry from the Chairman’s unsubstantiated assertion.
Most puzzling of all is the inclusion in the Chairman’s letter of quotes from the review comments from the National Academy of Sciences, NOAA and even the IPCC (though it is good to know he views that report as authoritative). One of the important features of this assessment is that it underwent an exhaustive review process and each and every one of the reviewers’ comments was addressed on the public record. In various drafts, there were questions raised, considered by the authors, and the report was clarified to adhere to the evidence and best analysis possible. Individual review comments are interesting, but don’t give a full picture of the report. It is a bit like looking at the weather on any one day or even a week and expecting it to represent a full picture of climate change. You have to look at the whole climate, Mr. Chairman, and the whole report, in order to fully see the evidence.
The House Committee on Science, Space and Technology should be, and has been in the past, an important venue for discussing the critical role science plays in our democratic government. Unfortunately, it has become increasingly partisan. A report like the National Climate Assessment, called for by Congress and developed by a very broad, non-partisan group of scientists from across the country, is exactly the type of independent advice we should expect in major policy debates. Of course people may differ on the choices society should make, but let’s look at the evidence fairly and objectively first.