Environmental Engineering Reference
In-Depth Information
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Global Mean Temperature Change (°C)
FIGURE Syn.1 Recent studies show that cumulative carbon dioxide emission is a useful metric for linking
emissions to impacts. Error bars reflect uncertainty in carbon cycle and climate responses to carbon dioxide
emissions due to observational constraints and the range of model results. Cumulative carbon emissions
are in teratonnes of carbon (trillion metric tonnes or 1,000 gigatonnes).
ppmv, 450 ppmv, etc.). This report concludes that, for a variety of conceptual
and practical reasons, it is more effective to assess climate stabilization goals
by using global mean temperature change as the primary metric. Global tem-
perature change can in turn be linked both to concentrations of atmospheric
carbon dioxide (Table 1) and to accumulated carbon emissions.
An important reason for using warming as a reference is that scientific
research suggests that many key impacts can be quantified for given tem-
BOX S
yn
-1 SUSTAINED WARMING COULD LEAD TO SEVERE IMPACTS
Widespread coastal flooding would be expected if warming of several degrees is sustained for
millennia. Model studies suggest that a cumulative carbon emission of about 1,000 to 3,000
gigatonnes (billion metric tonnes carbon) implies warming levels above about 2°C sustained
for millennia. This could lead to eventual sea level rise on the order of 1 to 4 m due to thermal
expansion of the oceans and to glacier and small ice cap loss alone. Melting of the Greenland
ice sheet could contribute an additional 4 to 7.5 m over many thousands of years.
