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5 December 2013 11:26 am ,
Vol. 342 ,
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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New Take on Climate Modeling
4 January 2002 (All day)
The world is getting hotter, and humans are at least partly to blame--but that's about all that climate researchers can confidently say about global warming. Their bottom-up approach--trying to understand the role of every part in the dizzyingly complex climate machine--has left the crucial question of how bad things could get unanswered. In the 4 January issue of Science, a group of researchers describe a new top-down approach: They plugged different combinations of values for fundamental properties of the climate system into a computer model and looked to see how well the model's output matched long-term observations. The results suggest that global warming is probably a serious threat and that it could get even hotter than most scientists believe.
Climate dynamicist Chris Forest of the Massachusetts Institute of Technology and his colleagues built a model of the climate between 1860 to 1995, when greenhouse gas levels soared, that included three adjustable variables. They picked various combinations of values for these variables, then ran the model and compared the outcomes with observed temperature records. The most disturbing finding comes from the team's analysis of climate sensitivity, in other words, how much global temperatures will increase given a certain amount of atmospheric carbon dioxide. If atmospheric carbon dioxide doubles the least temperature will rise is 1.4 kelvin--comparable to the long-cited, subjective 1.5 K lower limit recently repeated by the Intergovernmental Panel on Climate Change (IPCC) (ScienceNOW, 22 January 2001). At that level, "future changes in climate are of considerable concern," notes climatologist Tom Wigley of the National Center for Atmospheric Research in Boulder, Colorado. But the team came up with an upper limit even higher than the IPCC's: a scorching 7.7 K, compared with the IPCC's 4.5 K.
Another result is the ability of aerosols--microscopic particles found in pollutant hazes--to change solar heating of the atmosphere. Forest and his colleagues found that aerosols have most likely cooled the planet, by reflecting 0.30 to 0.95 watt per square meter of solar energy back into space; IPCC suggested that number could be as high as 4. If correct, Forest's modest cooling would mean that most of early greenhouse warming is not being masked by aerosols. But aerosol modeler Joyce Penner of the University of Michigan, Ann Arbor, cautions that Forest probably shouldn't be lumping all types of aerosols together.
The third variable--the rate at which the ocean takes up heat and counteracts greenhouse warming--couldn't be usefully constrained and needs more research, they write.