new analysis by scientists in the United States and England shows that there's a 90 percent likelihood that global average temperatures will rise 3-9 degrees Fahrenheit over the coming century, with an average increase slightly over five degrees.
As early as 2030 the planet is likely to heat up 1-2 degree, say the scientists.
"We are assigning probabilities to long-term projections to aid policy makers in assessing the risks that might accompany various courses of action or nonaction," says author Tom Wigley of the U.S. National Center for Atmospheric Research (NCAR). "If all scenarios are believed to be equally likely, it's difficult to plan."
An estimated global warming between about 2 - 10 degrees F was announced earlier this year by the Intergovernmental Panel on Climate Change (IPCC), composed of hundreds of scientists around the world. But the likelihood that the earth's temperature would warm only 2.5 degrees or as much as 10.4 degrees is very low, say NCAR's Wigley and coauthor Sarah Raper.
Even warming of 4-7 degrees F, however, is very large compared with the observed warming over the past century, which saw an increase of only one degree in the last 100 years.
"Whether or not such rapid warming will occur . . . depends on actions taken to control climate change," they write. In arriving at their estimates, the scientists assumed that no policies would be implemented to curb climate change before 2100.
If a rapid warming and its expected impacts occur in the near future, even swift societal attempts at control would yield little immediate success, say the authors. "The climate's inertia would lead to only a slow response to such efforts and guarantee that future warming would still be large," they say.
New estimates of sulfur dioxide and other emissions, along with updated information on carbon storage, ocean circulation, radiation, and other components of the earth system have improved computer models of the earth's climate and led the IPCC to both raise and widen its estimated range of global temperature increase. The panel's 1995 estimate was an increase between 1.4 - 6.3 degrees.
In their analysis Wigley and Raper attempted to interpret the likelihood of the new estimates, taking into account the wide uncertainties about future human activities and the climate's response to them. They identified the main sources of uncertainty and estimated the probability of their values falling within defined ranges. They then used these results to "drive" a simplified climate model and combined the various model results into probability ranges for temperature increases.
The study appears in the July 20 issue of the journal Science.
"Our research shows that, like many mosquitoes, this species breeds faster as the temperature gets higher," said Barry Alto, a University of Florida entomology doctoral student and co-author of the study appearing today in the Journal of Medical Entomology. "If global warming trends continue, the Asian tiger mosquito may become common in places where it's not found today.
What’s more, he said, the Asian tiger mosquito may be just the beginning.
"Some research indicates that global climate change may alter the current distributions of other mosquito species," Alto said.
Native to East Asia, the Asian tiger mosquito has spread widely in the last two decades, transported in shipments of used automobile tires containing its eggs, Alto said. Warmer regions of North and South America, Europe and Africa now harbor the species, known scientifically as Aedes albopictus. It was first reported in the United States in 1985 and has reached at least 25 states, mainly in the East and South.
"This mosquito spread quickly in the South," Alto said, "whereas in the Midwest, it's less common although it arrived in the mid-‘80s.”
The Asian tiger mosquito is named for its appearance, black with silver-white bands. Though small, the species is an aggressive biter, attacking humans, livestock and wildlife, mainly during daylight hours.
Phil Lounibos, a UF entomology professor who studies the Asian tiger mosquito, said it draws interest from researchers worldwide.
"So many places are affected by this insect," Lounibos said. "It would be just a nuisance except that it can transmit serious viral diseases."
In the tropics, the mosquito carries dengue fever, which infects tens of millions but is usually not fatal. A severe, hemorrhagic form of the disease infects hundreds of thousands each year and kills about 5 percent of those infected.
"Dengue is epidemic in northern and southeastern Brazil right now," Lounibos said. "We're trying to stop it. Competition between the Asian tiger mosquito and the yellow fever mosquito, another invasive species that transmits dengue, may play a role in the crisis."
Alto said the study compares reproduction of Asian tiger mosquitoes housed at 79, 75 or 72 degrees Fahrenheit. Mosquitoes kept at 79 degrees reproduced fastest, while those at 72 degrees reproduced slowest.
"The difference between the low and high temperatures -- 7 degrees -- matches some estimates of how much global temperatures will increase in the next 100 years," he said.
July 23, 2001 (http://www.monitor.net/monitor) All Rights Reserved. Contact firstname.lastname@example.org for permission to use in any format.
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