A small group of scientific critics contend that global warming studies have been flawed in many ways, and it is premature to form a solid conclusion. Two years ago, one such critic, geophysicist Richard Muller, professor of physics at the University of California at Berkeley, decided he would find out for himself, organizing and leading the Berkeley Earth Surface Temperature (BEST) study, partly funded by the Charles Koch Foundation, whose founder is a major funder of climate skeptics.
His objective: Gather and analyze worldwide historical land temperature measurements going back more than 200 years. He released his results earlier this month, concluding, the land is 1.6°F (1°C) warmer than in the 1950s. His numbers match with those of both NOAA and NASA, numbers cited by the majority of climate scientists. With the data now collected and analyzed, he is now convinced that the planet is warming.
Muller is presenting his results (four separate papers that are not yet published or peer-reviewed) to a conference in Santa Fe, New Mexico this week. The conference is expected to include many prominent skeptics as well as mainstream scientists.
AAAS MemberCentral had the opportunity to ask Muller about the BEST study. Here are his comments.
AAASMC: With what appeared to be a general scientific consensus on the reality of global warming, why did you decide to embark on this rather enormous project?
Professor of physics at University of California at Berkeley, Richard Muller: I think many people in the "consensus" joined that consensus because they were persuaded that the skeptics were simply anti-science, and that this issue was analogous to intelligent design. They were perhaps not aware that valid issues had been raised.
We found that there were several issues that needed addressing:
- Station quality — 70 percent of the temperature stations in the U.S. are ranked poor or worse.
- Station selection bias — less than 20 percent of the stations were included in previous studies. (I had a lot of experience with selection bias in my old bubble chamber days.)
- Homogenization — the adjustment of data to take into account documented and inferred station moves and instrument changes. These adjustments increased the magnitude of global warming, so it was important to know that they had been done properly.
- Urban heat island. We know that cities have warmed from both energy use and from sunlight absorption, but that is not related to greenhouse warming, and so it should not be included.
AAASMC: Many people received the news of your project's results with the reaction that now the global climate naysayers were proven wrong. Is this an overreaction, and if so, how would you describe the impact of your results?
Muller: That is certainly an overreaction. "Climategate" has not been exonerated by our work. The refusal to show discordant data by the people involved in that was not at the highest standards of science, and I was deeply disturbed by that.
We showed that global warming on land was close to what the prior groups had published. At first our results disagreed by about 0.2oC with NASA and HadCRU -- but we discussed it with NASA, and learned that their "land" average included averaging over the oceans. When they took this out, we got agreement.
(Having) extended the thermometer analysis back to 1800, we find significant disagreements with the hockey stick. We ... see much larger variability than they reported, and a temperature rise that started by 1800. The hockey stick plot is highly misleading. The hockey stick data are proxies, not the same as the thermometers that we used.
AAASMC: I understand that you have not addressed the question of origin or mechanisms for global warming. Do you have any personal beliefs or suspicions that you would care to share with us?
Muller: My sense is that much of the global warming of the last 50 years is caused by anthropogenic greenhouse enhancement. According to the IPCC (Intergovernmental Panel on Climate Change), it is "most" of the 0.64oC (that's a land-ocean average), and they put a 90 percent confidence level on that.
I worry that the IPCC did not sufficiently investigate enough potential "natural" causes for the warming, including (for example) long term variations in the thermohaline circulation. So I think the uncertainty is greater than they state.
I suspect it (anthropogenic warming) is between 50 percent and 80 percent of the observed warming, but that is just an educated guess. If it is 50 percent, then we have a lot more time to prepare than if it is 80 percent.
AAASMC: Your team is next intending to analyze the atmospheric temperatures over the waters of our planet. Do you at any point intend to tackle the various analyzes of the mechanisms/causes of global warming?
Muller: We would like to address the question of the human attribution. That depends very much on complex climate models, and it is a tough subject to study. It is very hard to tell whether the success of these models is due to their intrinsic accuracy, or to the fact that they have been highly adjusted over the years to account for the past climate changes. If it is the latter, then their true predictive powers haven't yet been proven.
Our analysis shows warming underway by 1800, large variations up and down throughout the 19th century, and that variability on the 3-15 year scale has been dramatically decreasing over the past two centuries. If those climate models had shown such behavior before our discovery of it, it would greatly enhance the world's confidence in those models. But in fact some of those models showed the opposite. That lessens our confidence in their predictive and explicative power.
AAASMC: Can you describe what this project means to you on a more personal level?
Muller: It is very satisfying to start out on a project that many people advised was hopeless, and to actually have such substantial results after two years.
On an even more personal level, it has been wonderful to work closely with my daughter Elizabeth. She and I together had the original idea of doing this project, and she has served as our executive director from the beginning.
It has also been wonderful to see and mentor the amazing work of Robert Rohde. His handling of the statistics was astonishing; he kept surprising us with his quick mastery of difficult statistical methods, and his creativity in adapting them to our data set. His paper on the method is, in the minds of the team members, a "masterwork.\" Robert has a great future, and I feel lucky to have been in the right place at the right time to mentor him into this extraordinary work.
Watch (above): Berkeley Earth video representation of the land surface temperature anomaly, 1800 to the present. The map of the world shows the temperature anomaly by location over time. The chart at the bottom, shows the global land-surface temperature anomaly. The Berkeley Earth analysis shows 0.911 degrees Centigrade of land warming (+/- 0.042 C) since the 1950s. (Source: Berkeley Earth)