Rose-tinted projections before summit

OSLO: Days ahead of a summit on climate change in Paris next week, many governments are citing scientific studies indicating that their plans to curb greenhouse gas emissions until 2030 will come within 0.7 degrees Celsius of an agreed 2C (3.6 Fahrenheit) target for limiting global warming this century.

Yet the studies they choose to quote are only the most optimistic of a range of projections, and presume that governments will go on to make even deeper emission cuts after 2030, which is far from certain.

With no action, a U.N. scientific panel estimates that the global average surface temperature in 2100 will be around 4.8C (8.6F) above pre-industrial times, dramatically increasing the frequency of extreme weather events and raising the sea level.

To avoid the worst of these effects, a ceiling of 2C has been agreed, and about 170 governments have submitted national plans before the Nov. 30-Dec. 11 summit to curb emissions from 2020-30.

Keen to show their policies will work, many cite two estimates that the pledges so far could limit the rise to 2.7C (4.9F).

U.S. Climate Envoy Todd Stern mentioned 2.7C in testimony to a Senate subcommittee last month, saying national policies marked “a powerful move in the right direction”.

Christiana Figueres, the head of the U.N. Climate Secretariat, summed up the national plans in a report last month by saying they “have the capability of limiting the forecast temperature rise to around 2.7 degrees Celsius by 2100”.

Yet Bill Hare, one of the scientists behind Climate Action Tracker (CAT), a group of four European institutes that first estimated 2.7C, said promises for action until 2030 “mark progress, but current policies are far from enough”.