Australian climate scientist Barry Pittock gave a terrific and terrifying talk at the 20th Anniversary of the Climate Insitute last week. He made the case that the U.N.’s Intergovernmental Panel on Climate Change (IPCC), the key international process for determining the “consensus” view on climate, is systematically underestimating the future impacts of climate change. Since Pittock was a major contributor to the IPCC’s Third Assessment Report (2001) and since their Fourth Assessment is due out next year, we should pay attention to what he says.
You can see all of Pittock’s 10 reasons online in the abstract for his talk. Let me pull out four of the underestimations:
1. “The climate sensitivity, or global warming after a doubling of the pre-industrial carbon dioxide concentration, is probably in the range of 2º–6°C rather than the 2001 IPCC estimate of 1.5º–4.5ºC. This suggests a more than 50% chance of that global warming by 2100 will be 3ºC or more, a level that many consider dangerous.”
3. “Permafrost melting is widespread,” which “leads to emissions of carbon dioxide and methane,” a dangerous vicious climate cycle that CP has written about.
7. & 8. “Rapid changes in Antarctica” and “Rapid melting and faster outlet glaciers in Greenland,” which combine to threaten far faster and greater sea level rise than climate models have been predicting.
I found his talk very compelling as it matched what I’ve been hearing from a number of climate scientists I interviewed for my book, including James Hansen. Pittock concludes:
The above lines of evidence (supported by well over 100 recent scientific papers), while not definitive and in some cases controversial, suggest that the balance of evidence may be swinging toward a more extreme outcome. While some of the observations may be due merely to natural fluctuations, their conjunction and, in several cases, amplifying effects are causes for concern. They suggest that critical levels of global warming may occur at even lower greenhouse gas concentrations and emissions than was considered justified in the Third Assessment Report of the Intergovernmental Panel on Climate Change report issued in 2001.
In short, the time for inaction has run out.
For those interested in Pittock’s analysis, he published a version in EOS, but you need a subscription. You can, however, get all the scientific references here. The article ends with a key point that he reiterated in his talk, which defines the nature of scientific responsibility in a world of accelerating global warming:
The above recent developments simply might mean that the science is progressing, but it also may suggest that up until now many scientists may have consciously or unconsciously downplayed the more extreme possibilities at the high end of the uncertainty range, in an attempt to appear moderate and ‘responsible’ (that is, to avoid scaring people). However, true responsibility is to provide evidence of what must be avoided: to define, quantify, and warn against possible dangerous or unacceptable outcomes.