Long-Term Use of Fossil Fuels Could Raise Earth Temperature by 8º C
1 November 2005
|LLNL model shows a mean surface temperature increase to 7.8°C by 2300, with spikes in polar regions.|
According to a recent modelling and simulation performed by scientists at Lawrence Livermore National Laboratory, business-as-usual consumption of fossil fuels for the next few centuries would result in the depletion of the polar ice caps, a rise in ocean sea levels by seven meters, and an increase in the median air temperature of 8º C (14.5º F).
In the polar regions alone, the temperature would spike more than 20º Celsius (36º F), forcing the land in the region to change from ice and tundra to boreal forests.
The temperature estimate is actually conservative because the model didn’t take into consideration changing land use such as deforestation and build-out of cities into outlying wilderness areas.—lead author Govindasamy Bala, LLNL Energy and Environment Directorate
Today’s level of atmospheric carbon dioxide is 380 parts per million (ppm). By the year 2300, the model predicts that amount would nearly quadruple to 1,423 ppm.
In the simulations, soil and living biomass are net carbon sinks, which would extract a significant amount of carbon dioxide that otherwise would remain in the atmosphere from the burning of fossil fuels. The real scenario, however, might be a bit different.
The land ecosystem would not take up as much carbon dioxide as the model assumes. In fact in the model, it takes up much more carbon than it would in the real world because the model did not have nitrogen/nutrient limitations to uptake. We also didn’t take into account land use changes, such as the clearing of forests.—Govindasamy Bala
The model shows that ocean uptake of CO2 begins to decrease in the 22nd and 23rd centuries due to the warming of the ocean surface that drives CO2 fluctuations out of the ocean. The ocean takes longer to absorb CO2 than do biomass and soil.
By the year 2300, about 38% and 17% of the carbon dioxide released from the burning of all fossil fuels are taken up by land and the ocean, respectively. The remaining 45% stays in the atmosphere.
Whether carbon dioxide is released in the atmosphere or the ocean, eventually about 80 percent of CO2 will end up in the ocean in a form that will make the ocean more acidic. While the carbon dioxide is in the atmosphere, it could produce adverse climate change. When it enters the ocean, the acidification could be harmful to marine life.
The models predict quite a drastic change not only in the temperature of the oceans but also in its acidity content, which would become especially harmful for marine organisms with shells and skeletal material made out of calcium carbonate.
Calcium carbonate organisms, such as coral, serve as climate stabilizers. When the organisms die, their carbonate shells and skeletons settle to the ocean floor, where some dissolve and some are buried in sediments. These deposits help regulate the chemistry of the ocean and the amount of carbon dioxide in the atmosphere. Earlier Livermore research, however, found that unrestrained release of fossil-fuel carbon dioxide to the atmosphere could threaten extinction for these climate-stabilizing marine organisms.
The doubled-CO2 climate that scientists have warned about for decades is beginning to look like a goal we might attain if we work hard to limit CO2 emissions, rather than the terrible outcome that might occur if we do nothing.—Ken Caldeira, Department of Global Ecology, Carnegie Institution
The research appears in the 1 Nov issue of the American Meteorological Society’s Journal of Climate.
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