US budget experts say long-term climate figures may be off by 50%

Washington (Platts)--16Nov2007


There is massive uncertainty in long-term projections of greenhouse gas
emissions and how the climate will respond to the build-up of GHGs in the
atmosphere, according to analysis by the Congressional Budget Office.

Speaking at a CBO conference in Washington Friday, CBO Director Peter
Orszag said the damage GHG will cause to the climate depends on the future of
global population, technological developments and economic growth.

"As a result of those uncertainties, any projection of cumulative
emissions of [GHGs] (measured in terms of carbon dioxide equivalent) over the
next century could easily err by plus or minus 50%," the presentation showed.

"The accumulation in the atmosphere also depends on how rapidly they will
be absorbed by the oceans and forests--another source of significant
uncertainty," according to the presentation.

In light of the uncertainties of predicting emissions and the earth's
reaction to them, there is an equal amount of confusion on exactly how carbon
releases will affect the global climate, CBO said.

"Given the current uncertainties, any projection of the climate's full
response to a given increase in [GHG] concentrations could err by plus or
minus 50%. Moreover, that full response will unfold at an uncertain pace for
decades," it said.

The major uncertainties in emissions and climate change "complicate the
process of setting realistic goals for climate policy," according to Orszag's
presentation.

"The difficulty in taking action to address climate change stems from the
fact that reaching emissions targets cannot guarantee that atmospheric GHG
targets will be achieved. And even if atmospheric targets are met, there's no
certainty that the temperature target will be met," the presentation said.

Climate change will benefit some particularly cold areas where winters
are likely to be mild and growing seasons are likely to be longer, CBO said.
But "many of the changes are likely to impose economic and social costs in
other regions--for example, by melting ice caps and ice sheets," raising seas
levels and altering ecology, it said.

--Martin Coyne, martin_coyne@platts.com