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GFDL Model
Recent results from the GFDL
model for temperature
change (Figure 2) from 1850 to 2000 show that the model
is able to capture quite well the average behavior over this period. The spatial distribution of
warming in the GFDL transient model (Figure 3) at the time of CO2 doubling shows that warming is most pronounced in the
polar region of the northern hemisphere. The surface warming also leads to substantial decrease in
sea ice coverage over the Arctic Ocean (Figure 4). Mean sea ice thickness (in meters) in this figure is the model result for late winter and is shown for both
the control and 4xCO2 experiments.
Simulated changes in sea level Figure 5 due to thermal expansion of oceans show a 25 cm rise over 100 years and over 1 m rise in 500 years for a doubling of CO2 as the deep ocean gradually warms in response to surface warming. Adding increased ocean water volume due to melting of ice that presently is above sea level could add substantially to sea-level rise, but these calculations currently have large uncertainty. The effect of sea-level rise on the SE and Gulf Coasts (Figure 6) of the US from the GFDL projections will first be observed in Florida and North and South Carolina.
The GFDL model has an ocean circulation component that enables us to see the effect of warming on ocean circulation Figure 7. The model simulations project global thermohaline circulation to decrease in intensity with increased greenhouse gas warming due to enhanced precipitation and runoff from the continents in high latitudes.
The GFDL model (Figure 8) projects substantial decreases in soil moisture over most mid-latitude continental areas during summer with global warming . Soil moisture reductions in major agricultural areas could negatively impact global food production as will be discussed in Unit 3-6.
Surface air temperatures (Figure 9) for a doubling of CO2 in the GFDL model are projected to rise by about 7°C in the southeast US in July, which will significantly add to human discomfort as represented by the heat stress index (Figure 10).
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