Back in June, an article on Bloomberg had some pretty fun charts that purport to unequivocally demonstrate that man and his CO2 emissions are wholly responsible for Earth’s warming since 1880. Every few weeks another friend seems to stumble across this article and share it. I’ve been offering them all friendly explanations about the reality of these charts, but thought I ought to blog on the topic before another friend posts the same link.
What the authors, Roston and Migliozzi, are doing is finding something that correlates reasonably well with NASA’s temperature series data, but may not in fact prove anything. There’s a pretty hilarious site that demonstrates what I mean. For example, annual per capita cheese consumption correlates strongly with the number of people who die each year by becoming tangled in their bedsheets!
When I first saw this Bloomberg article back in June, I commented to a friend, “Fun charts, but if you look at them closely, you still don’t get a convincing answer to the questions the IPCC still struggles to explain: the warming from 1910 to 1940, the cooling from 1940 to 1975, and the plateau from 1997 to present.” In other words, the correlation isn’t very good during these time periods, including the one we’re in right now where CO2 output has been rising rapidly for the past couple of decades and global temperatures have been flat for 18 years and counting.
As I’ve written before, I’m not a global warming “denier” at all. It’s clear there’s been a long warming trend. The big question is man’s role. Have we got nothing to do with it, a little to do with it or a lot? My reading of the science suggests that perhaps we have a little to do with it, but most of it’s natural variability.
In their comments to my responses to these charts some people have shared articles like this one that attempt to explain the issues with the charts that I raised above. However, other scientists have different explanations. For example, this article from earlier this month that summarizes the history of global warming science along with some of the latest papers on the topic. It states:
“Scientists at the Climate and Environmental Physics and Oeschger Centre for Climate Change Research at the University of Berne in Switzerland have recently backed up theories that support the sun’s importance in determining the climate on Earth. A paper published last year by the American Meteorological Society contradicts claims by IPCC scientists that the sun couldn’t be responsible for major shifts in climate. Judith Curry, chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology, rejected IPCC assertions that solar variations don’t matter. Among the many studies and authorities she cited was the National Research Council’s recent report “The Effects of Solar Variability on Earth’s Climate”.
“Other researchers and organisations are also predicting global cooling – the Russian Academy of Science, the Astronomical Institute of the Slovak Academy of Scientists, the Institute of Terrestrial Magnetism Russia, Victor Manuel Velesco Herrera at the National University of Mexico, the Bulgarian Institute of Astronomy, Dr Tim Patterson at Carleton University in Canada, Drs Lin Zhen at Nanjing University in China, just to name a few.”
The aforementioned Judith Curry also discussed the science in a Wall Street Journal article entitled “The global warming statistical meltdown“:
“More than a dozen…observation-based studies have found climate sensitivity values lower than those determined using global climate models, including recent papers published in Environmentrics (2012),Nature Geoscience (2013) and Earth Systems Dynamics (2014). These new climate sensitivity estimates add to the growing evidence that climate models are running “too hot.” Moreover, the estimates in these empirical studies are being borne out by the much-discussed “pause” or “hiatus” in global warming—the period since 1998 during which global average surface temperatures have not significantly increased.”
But wait, some of you might say, I’ve heard that “97% of scientists agree that man is responsible for global warming.” This claim relies on an incredibly questionable study that many people have revealed is bogus. Alex Epstein does a terrific job summarizing why it’s nonsense. For example, when you look at the actual scientific papers used to support the claim, you discover, as he writes, that in fact only “1.6 percent explicitly stated that man-made greenhouse gases caused at least 50 percent of global warming.” In fact only a handful of the dozens of papers cited in the study give any opinion as to whether man is responsible and how much he is contributing to global warming.