Prominent global warming activist James Hansen admits in a new paper that world temperatures are not warming as fast as predicted by the United Nations Intergovernmental Panel on Climate Change (IPCC).
Emissions, Temperatures Diverge
“Annual fossil fuel CO2 emissions have shot up in the past decade at about 3% [per] yr, double the rate of the prior three decades. The growth rate falls above the range of the IPCC (2001) ‘Marker’ scenarios,” Hansen reports.
Nevertheless, “the rate of global warming seems to be less this decade than it has been during the prior quarter century,” Hansen admits. The slower pace of warming contradicts IPCC computer models projecting accelerating global warming.
Slower Carbon Dioxide Accumulation
Hansen reports atmospheric carbon dioxide is not rising as rapidly as the growth in carbon dioxide emissions. The slower-than-expected atmospheric accumulation likely explains the slowdown in global warming, Hansen claims.
Hansen divided the ratio of atmospheric carbon dioxide increase by annual fossil fuel-related carbon dioxide emissions. Hansen labeled the result of this equation the “airborne fraction.”
“Remarkably, and we will argue importantly, the airborne fraction has declined since 2000 during a period without any large volcanic eruptions,” Hansen writes.
“The 7-year running mean of the airborne fraction had remained close to 60% up to 2000, except for the period affected by Pinatubo,” Hansen observes. “The airborne fraction is affected by factors other than the efficiency of carbon sinks, most notably by changes in the rate of fossil fuel emissions (Gloor et al 2010). However, it is the dependence of the airborne fraction on fossil fuel emission rate that makes the post-2000 downturn of the airborne fraction particularly striking. The change of emission rate in 2000 from 1.5% [per] yr to 3.1% [per] year, other things being equal, would have caused a sharp increase of the airborne fraction (the simple reason being that a rapid source increase provides less time for carbon to be moved downward out of the ocean’s upper layers).”
Coal Emissions Aiding Plant Growth
Soil, plants, and other factors absorb carbon from the atmosphere, which scientists refer to as carbon sinks. Hansen speculates a large recent increase in carbon sinks is responsible for the declining airborne fraction. Importantly, he links the speculated increase in carbon sinks to more coal power generation, particularly in Third World nations.
“We suggest that the huge post-2000 increase of uptake by the carbon sinks … is related to the simultaneous sharp increase in coal use,” Hansen writes.
Despite many environmental activist groups’ aggressive opposition to coal power plants, Hansen reports coal emissions benefit plant growth, which in turn absorbs increasing amounts of atmospheric carbon.
“We suggest that the surge of fossil fuel use, mainly coal, since 2000 is a basic cause of the large increase of carbon uptake by the combined terrestrial and ocean carbon sinks. One mechanism by which fossil fuel emissions increase carbon uptake is by fertilizing the biosphere via provision of nutrients essential for tissue building, especially nitrogen, which plays a critical role in controlling net primary productivity and is limited in many ecosystems,” Hansen explains.
“Modeling and field studies confirm a major role of nitrogen deposition, working in concert with CO2 fertilization, in causing a large increase in net primary productivity of temperate and boreal forests,” Hansen writes.
Hansen’s assessment supports the findings of scientists Sherwood Idso and Craig Idso that rising atmospheric carbon dioxide content is fertilizing plant growth and stimulating the biosphere. Rising global crop yields and retreating desserts are among the observed benefits of such plant fertilization.
Methane Accumulation Slowing
Hansen also reports atmospheric methane is rising more slowly than IPCC predictions. Methane is one of the atmospheric gases most effective in trapping heat in the atmosphere. A longterm slowdown in atmospheric methane accumulation would substantially mitigate future warming projections.
“Atmospheric CH4 [methane] is increasing more slowly than in IPCC scenarios, which were defined more than a decade ago (IPCC 2001),” Hansen observes.
“There are anthropogenic sources of CH4 that potentially could be reduced, indeed, the leveling off of CH4 amount during the past 20 years seems to have been caused by decreased venting in oil fields,” Hansen writes.
Facts Contradict IPPC
The slowdown in atmospheric methane accumulation contradicts IPCC computer models projecting a cycle of accelerating atmospheric methane growth that feeds upon itself. According to theories incorporated in IPCC models, rising global temperatures will release methane that has been frozen in tundra and polar sea beds. The new sources of atmospheric methane will cause further warming, which will in turn cause the release of additional methane. This positive feedback loop is a key component in global warming projections.
Hansen says the combination of growing carbon sinks and a reduction in atmospheric methane accumulation explain the slowdown in global warming that has befuddled global warming activists.
“The growth rate for the total climate forcing by well-mixed greenhouse gases has remained below the peak values reached in the 1970s and early 1980s, has been relatively stable for about 20 years, and is falling below IPCC (2001) scenarios,” Hansen writes.
Not retreating from his longstanding global warming alarmism, however, Hansen speculates plant life may soon stop benefiting from atmospheric fertilization and global warming may resume its prior pace.
James M. Taylor ([email protected]) is managing editor of Environment & Climate News.
“Climate forcing growth rates: doubling down on our Faustian bargain,” Environmental Research Letters, http://iopscience.iop.org/1748-9326/8/1/011006