There is not much new in a collection of articles about global warming and sea level rise in the latest issue of Science. As such, it is mostly recycled and repackaged information that the head of the American Association for the Advancement of Science (AAAS), Donald Kennedy, can take down from New York Avenue in DC to Capitol Hill, to scare politicians into doing what it wants, which is an immediate cap on U.S. emissions of carbon dioxide.
Never mind that even a 25% reduction will have an undetectable effect on the rate of global temperature rise in the foreseeable future, and that it will cost a lot. Science crammed its March 24th issue with five articles (including commentary and editorials) devoted to melting ice and sea level rise—including one (Overpeck et al., 2006) which proclaims “[I]t is highly likely that the ice sheet changes described in this paper [leading to an—egad—global sea level a rise of 12-18 feet] could be avoided if humans were to significantly reduce emissions early in the current century” is hardly surprising.
Here’s the logic. 130,000 years ago, during the last interglacial period, there is evidence that sea levels were 12-18 feet higher than they are now. This extra water must have come from loss of ice from Greenland and Antarctica. His climate model shows us that temperatures were higher in the Arctic 130,000 years ago than today. It also shows that by the year 2100 temperature in the Arctic will be higher than they were 130,000 years ago.
Sell the beach house. Pronto.
There is nothing new here. The scientific literature is littered of references to the fact that sea levels were much higher in previous interglacials than in the current one, that previous interglacials were warmer than the current one, and that climate models project rising temperatures in the future (especially when run with unrealistic carbon dioxide growth rates such as those used by Overpeck et al.).
What could have been new, would have been if Overpeck et al. had run their climate model with carbon dioxide (CO2) increases that bore some resemblance to reality. Overpeck et al. defend their use a 1%/year increase in atmospheric carbon dioxide levels with “We note that this commonly-used estimate of future CO2 increase (as a proxy for the combined increases of CO2, CH4, N2O and other increasing greenhouse gases) is well within the range of plausible future greenhouse gas increase scenarios estimated by the IPCC.” But this is weak defense indeed (note: the 1%/yr scenario produces greenhouse gas increases that lie near the top end of the IPCC scenarios).
The actual annual increases in carbon dioxide in the last ten years averaged 0.49%. It was 0.42% in the ten years before that, and 0.43% between twenty and thirty years ago. (Those who see some constancy in these numbers need not get their eyes checked).
Couple this with the fact that it takes at least 50 years to fully realize the warming from an increment of carbon dioxide and it must be true that the models are predicting too much warming for the foreseeable future.
Think we’re making it up? NASA’s suppressed climate modeler and election campaign worker (see here) Jim Hansen did manage to get out the following statement a few years ago (in naturalscience.com):
“There are reasons to believe that the IPCC scenarios are unduly pessimistic. First, they ignore changes in emissions, some already underway, due to concerns about global warming. Second, they assume that true air pollution will continue to get worse, with O3, CH4 and black carbon all greater in 2050 than in 2000. Third, they give a short shrift to technology advances that can reduce emission in the next 50 years. An alternative way to define scenarios is to examine current trends in climate forcing agents…Th[e] ‘current trends’ growth rate of climate forcings…is at the low end of the IPCC range…”
Further comment on the use of a 1%/yr scenario is given by Covey et al. (2003) in describing the results from a collection of climate model results all run with this scenario (CMIP2):
“The rate of radiative forcing increase implied by 1% per year increasing CO2 is nearly a factor of two greater than the actual anthropogenic forcing in recent decades, even if non-CO2 greenhouse gases are added in as part of an ‘equivalent CO2 forcing’ and anthropogenic aerosols are ignored (see, e.g., Figure 3 of Hansen et al. 1997). Thus the CMIP2 increasing-CO2 scenario cannot be considered as realistic for purposes of comparing model-predicted and observed climate changes during the past century. It is also not a good estimate of future anthropogenic climate forcing, except perhaps as an extreme case in which the world accelerates its consumption of fossil fuels while reducing its production of anthropogenic aerosols.”
So, Overpeck et al.’s justification doesn’t really cut it. But it does produce a dramatic result, tripling the concentration of atmospheric CO2 concentration by 2100 and a quadrupling (!) it by 2130. With current trends, that would happen in year 2269. By then, energy-production technology probably will probably have turned over two or three times and this will never have become an issue.
Really, what all of this hub-bub boils down to is regurgitating old news with a becoming-all-to-familiar new twist—things are always going to be much worse than we ever imagined—a mathematical impossibility, by the way. But, who cares if it gets the policy that AAAS wants? That’s what New York Avenue lobbyists are for—to get politicians to do what they and their supporters desire.
Covey, C., K. M. AchutaRao, U. Cusbasch, P. Jones, S. J. Lambert, M. E. Mann, T. J. Phillips, and K. E. Taylor, 2003: An overview of Results from the Coupled Model Intercomparison Project (CMIP). Global and Planetary Change, 37, 103-133.
Hansen, J.E., 2003. Can we defuse the global warming time bomb? Natural Science, www.naturalscience.com/ns/articles/01-16/ns_jeh.html
Overpeck, J.T., et al., 2006. Paleoclimatic evidence for future ice-sheet instability and rapid sea-level rise. Science, 311, 1747-1750.