Bedritsky states that “human activities are altering the climate at an increasingly alarming rate.” However, according to data from the United Nations Intergovernmental Panel on Climate Change (IPCC), the rate of planetary warming that was established in the mid-1970s has been remarkably constant, varying only slightly from 0.17°C per decade.
The 21 computer models used by the IPCC share a common ensemble characteristic: for the midrange emissions scenario they, too, predict a constant rate of warming, not an “increasing” rate. The models simply produce different rates. As a meteorologist, Bedritsky knows that the way to adjudicate between differing forecast models is to literally “look out the window” to see which is performing the best. In the case of climate models, looking at the warming trend that has been established accomplishes the same, and yields a 21st century warming of 1.7°C, which is within, but near the low end, of the entire range of projections made by the IPCC.
Even this may be an overestimation. It is very clear, from both the IPCC data and from satellite measurements, that there has been no net warming since 1998 (which was a record year because of a very strong El Niño warming in the tropical Pacific). Further, as noted by Keenlyside et al. in Nature earlier this year, Atlantic and Pacific temperature patterns indicate that little warming can be expected for several more years. Many of the IPCC’s climate models are indeed capable of reproducing El Niño-like temperature excursions, but none—not one—of the models illustrated in the IPCC’s 2007 report projects a period of 15 years with no net warming.
Bedritsky’s statement about a “marked decline” of global ice cover is also contextually incomplete. Sea-ice in the Northern Hemisphere, mainly in the Arctic Ocean, has declined significantly since systematic measurements began in 1979, but 1979 was at the end of the coldest period in the Arctic since the mid-1920s. While the recent decline is clearly related to warming temperatures, paleoclimatic evidence from northern Eurasia indicates that late summer sea-ice in the Arctic was likely to have been very spotty or non-existent for millennia after the end of the last ice age. Obviously the polar bear and the Inuit survived. Ice extent measured by satellite in the Southern Hemisphere has increased and was at record high levels, adjusted for season, earlier this year.
I think Bedritsky’s article would have been more complete, if less alarming, if he had noted these observations about climate history, climate models, and ice.
Their omission reminds me of President Eisenhower’s fears that a technological elite could acquire inordinate power. In his farewell address,famous for its introduction of the notion of a “military-industrial” complex, Eisenhower went on to say something equally prescient and disturbing, “Holding scientific research and discovery in respect, as we should, we must always be alert to the equal and opposite danger that public policy could itself become a captive of a scientific-technological elite.”
This is precisely the danger that accrues when authoritative scientists do not communicate complete information to the public.
