Is climate change an impending major calamity, threatening massive economic and ecological costs that could virtually wipe out mankind? Or is it a conspiracy of liberal scientists bent on hobbling the American economy and imposing green socialism worldwide?
For a long time, I’ve held to a middle-of-the-road view—though it’s caused me to be labelled both a gullible alarmist and a “climate denier” over the years. That view, in short, is this: Climate change is real but slow, partially man-made but partially natural, and potentially harmful but more likely a wash.
While you won’t see it reflected in the headlines about the release of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, part of which was unveiled today in Stockholm, even the IPCC’s authors are tip-toeing toward those of us in the muddled middle.
The report, in many ways, is a bit of a strange document. Its authors say they are more certain than they were in their last report, issued in 2007, that climate change is (and will be) slower and less severe than previously thought. They also say they are more certain of greater uncertainty about how much climate change will occur. Got that?
In all sorts of ways, the report climbs down from what was said six years ago, yet like any bureaucratic committee, it does its utmost to disguise these retreats. Professor Ross McKitrick of Guelph University, an economist and forecaster who has made a specialty of examining and challenging the IPCC’s pronouncements, summarizes the latest proclamation thus: “Since we started in 1990 we were right about the Arctic, wrong about the Antarctic, wrong about the tropical troposphere, wrong about the surface, wrong about hurricanes, wrong about the Himalayas, wrong about sensitivity, clueless on clouds and useless on regional trends. And on that basis we’re 95% confident we’re right.”
Actually, the IPCC is 95% sure—not that Armageddon is inevitable, but merely that “human influence on climate caused more than half of the observed increase in global average surface temperature from 1951−2010.” This is not a statement about the future at all; it is a statement about the past. Many seem not to have spotted the distinction. This is about as underwhelming a claim as can be made, meaning much less than half a degree Celsius of change since soon after the end of World War II is down to mankind. There are very few people who would disagree with this remark, even in the most skeptical circles. To trumpet it as a new cause of alarm is bizarre.
So here are some of the things the IPCC has now conceded:
- Global average temperatures did not rise at all for the last 15 years. “Models do not generally reproduce the observed reduction in surface warming trend over the last 10 –15 years.” This was a fact skeptics were vilified for pointing out just two years ago.
- Climate sensitivity (the amount of warming likely to be caused eventually, if carbon dioxide levels double) can no longer even be calculated. “No best estimate for equilibrium climate sensitivity can now be given because of a lack of agreement on values across assessed lines of evidence and studies.” The bottom end of the range of probable climate sensitivity has been lowered, however, from 2 degrees Celsius to 1.5 degrees Celsius, while the top end remains the same: 4.5 degrees Celsius. This broadens the range of possible outcomes—that is, increases the uncertainty.
- Transient climate response (the actual warming likely to be experienced by around 2080 if carbon dioxide levels have doubled from pre-industrial levels by that time) is now thought to be less than they thought four years before. It is now thought to be in the range 1 to 2.5 degrees Celsius, rather than 1 to 3 degrees Celsius.
- Antarctic sea ice increased, instead of decreasing as predicted: “Most models simulate a small downward trend in Antarctic sea ice extent, albeit with large inter-model spread, in contrast to the small upward trend in observations.” This is awkward. If the models get the Antarctic wrong, then maybe they got the Arctic right by accident.
- The big concession is the one the one IPCC cannot quite bring itself to be explicit about: the failure of the models to match reality. The text of the summary released today says: “The long-term climate model simulations show a trend in global-mean surface temperature from 1951 to 2012 that agrees with the observed trend (very high confidence). There are, however, differences between simulated and observed trends over periods as short as 10 to 15 years.” Yet a chart in the draft of its full report, due out on Monday, tells a very different story, of actual temperature measurements over the past 23 years falling below the projections made on each of four previous occasions. Its own chart says, in other words, that it is unlikely that the models are right.
It’s a shame the climate debate remains so heated. Perhaps someday the rhetoric surrounding climate change can cool down to reflect the modesty of the predictions we’re actually able to make.