Written By: Roy Spencer, Ph.D.
Published In: Environment & Climate News > October 2008
Publication date: 10/09/2008
Publisher: The Heartland Institute
Roy Spencer, Ph.D., U.S. Science Team Leader for the National Aeronautic and Space Administration’s collection of satellite temperature data and a principal research scientist at the University of Alabama at Huntsville’s Earth System Science Center, on July 22 told the U.S. Senate Environment and Public Works Committee why the scientific data lead him to conclude global warming is not a crisis.
An abbreviated version of Spencer’s testimony is published below. Spencer will expand on this testimony at the 2009 International Conference on Climate Change, scheduled for March 8-10 in New York City.
Regarding the currently popular theory that mankind is responsible for global warming, I am very pleased to deliver good news from the front lines of climate change research. Our latest research results, which I am about to describe, could have an enormous impact on policy decisions regarding greenhouse gas emissions.
Despite decades of persistent uncertainty over how sensitive the climate system is to increasing concentrations of carbon dioxide from the burning of fossil fuels, we now have new satellite evidence which strongly suggests that the climate system is much less sensitive than is claimed by the U.N.’s Intergovernmental Panel on Climate Change (IPCC).
Another way of saying this is that the real climate system appears to be dominated by “negative feedbacks”—instead of the “positive feedbacks” which are displayed by all 20 computerized climate models utilized by the IPCC. (Feedback parameters larger than 3.3 Watts per square meter per degree Kelvin (Wm-2K-1) indicate negative feedback, while feedback parameters smaller than 3.3 indicate positive feedback.)
If true, an insensitive climate system would mean that we have little to worry about in the way of manmade global warming and associated climate change. And, as we will see, it would also mean that the warming we have experienced in the last 100 years is mostly natural. Of course, if climate change is mostly natural then it is largely out of our control, and is likely to end—if it has not ended already, since satellite-measured global temperatures have not warmed for at least seven years now.
Climate Sensitivity Overestimated
The support for my claim of low climate sensitivity (net negative feedback) for our climate system is twofold. First, we have a new research article in-press in the Journal of Climate which uses a simple climate model to show that previous estimates of the sensitivity of the climate system from satellite data were biased toward the high side by the neglect of natural cloud variability. It turns out that the failure to account for natural, chaotic cloud variability generated internal to the climate system will always lead to the illusion of a climate system which appears more sensitive than it really is.
The second line of evidence in support of an insensitive climate system comes from the satellite data themselves. While our work in-press established the existence of an observational bias in estimates of climate sensitivity, it did not address just how large that bias might be.
But in the last several weeks, we have stumbled upon clear and convincing observational evidence of particularly strong negative feedback (low climate sensitivity) from our latest and best satellite instruments. That evidence includes our development of two new methods for extracting the feedback signal from either observational or climate model data, a goal which has been called the “holy grail” of climate research.
Based upon global oceanic climate variations measured by a variety of NASA and NOAA [National Oceanic and Atmospheric Administration] satellites during the period 2000 through 2005 we have found a signature of climate sensitivity so low that it would reduce future global warming projections to below 1 deg. C by the year 2100. ... [T]hat estimate from satellite data is much less sensitive (a larger diagnosed feedback) than even the least sensitive of the 20 climate models which the IPCC summarizes in its report. It is also consistent with our previously published analysis of feedbacks associated with tropical intraseasonal oscillations.
IPCC Ignored Alternative Explanations
One necessary result of low climate sensitivity is that the radiative forcing from greenhouse gas emissions in the last century is not nearly enough to explain the upward trend of 0.7 deg. C in the last 100 years. This raises the question of whether there are natural processes at work which have caused most of that warming.
On this issue, it can be shown with a simple climate model that small cloud fluctuations assumed to occur with two modes of natural climate variability—the El Niño/La Niña phenomenon (Southern Oscillation), and the Pacific Decadal Oscillation—can explain 70 percent of the warming trend since 1900, as well as the nature of that trend: warming until the 1940s, no warming until the 1970s, and resumed warming since then.
While this is not necessarily being presented as the only explanation for most of the warming in the last century, it does illustrate that there are potential explanations for recent warming other that just manmade greenhouse gas emissions. Significantly, this is an issue on which the IPCC has remained almost entirely silent. There has been virtually no published work on the possible role of internal climate variations in the warming of the last century.
While it will take some time for the research community to digest this new information, it must be mentioned that new research contradicting the latest IPCC report is entirely consistent with the normal course of scientific progress. I predict that in the coming years, there will be a growing realization among the global warming research community that most of the climate change we have observed is natural, and that mankind’s role is relatively minor.
I hope that the Committee realizes that, if true, these new results mean that humanity will be largely spared the negative consequences of human-induced climate change. This would be good news that should be celebrated—not attacked and maligned.
And given that virtually no research into possible natural explanations for global warming has been performed, it is time for scientific objectivity and integrity to be restored to the field of global warming research. This Committee could, at a minimum, make a statement that encourages that goal.
For more information ...
Video of the testimony of NASA’s Dr. Roy Spencer before the U.S. Senate Environment and Public Works Committee on July 22, 2008: http://www.youtube.com/watch?v=Qzf6z-oHP8U
Text of the complete testimony of NASA’s Dr. Roy Spencer before the U.S. Senate Environment and Public Works Committee on July 22, 2008: http://epw.senate.gov/public/index.cfm?FuseAction=Files.View&FileStore_id=e12b56cb-4c7b-4c21-bd4a-7afbc4ee72f3