LONDON (Reuters) - The chance of limiting the rise in global temperatures to 2 degrees Celsius this century is getting slimmer and slimmer, the head of the International Energy Agency warned on Wednesday.
"What I see now with existing investments for plants under construction...we are seeing the door for a 2 degree Celsius target about to be closed and closed forever," Fatih Birol, the IEA's chief economist, told a Reuters' Global Energy & Environment Summit.
"This door is getting slimmer and slimmer in terms of physical and economic possibility," he warned.
The IEA said last November that around 80 percent of total energy-related carbon emissions permissible by 2035 to limit warming were already accounted for by existing power plants, buildings and factories, leaving little room for more.
In 2010, countries agreed that deep emissions cuts had to be made to keep an increase in global average temperature below 2 degrees Celsius above pre-industrial levels this century.
Scientists say that crossing the threshold risks an unstable climate in which weather extremes are common but efforts so far to cut greenhouse gas emissions are not seen as sufficient to stop a rise beyond 2 degrees.
A report this month by the Club of Rome think tank said rising carbon dioxide emissions will cause a 2 degree rise by 2052 and a 2.8 degree rise by 2080, though some other estimates are more conservative.
Some countries are focusing on domestic economic pressures, which could delay climate action and add to the cost of fighting climate change in the long-run.
"One dollar not invested now in reducing C02 will cost 4.6 dollars in the next decade to achieve the same effect," Birol said.
A major reason for rising carbon dioxide emissions was fossil fuel subsidies, he added.
In 2012, $630 billion was spent on fossil fuel subsidies globally, with half of this from the Middle East and the other half from the rest of the world, Birol said.
"By contrast, in 2010, fuel subsidies totalled $400 billion. We are going backwards," he said.
Birol's 2012 figure overshoots his forecast last year that fossil fuel subsidies would reach $660 billion by 2020, or 0.7 percent of global gross domestic product.
The pressure is on governments to phase out fossil fuel subsidies. Eliminating them by 2020 would cut global energy demand by 4 percent and considerably reduce carbon emissions growth, according to the IEA.
The G20 nations agreed in 2009 to phase out inefficient fossil fuel subsidies that encourage wasteful consumption over the medium term to foster green growth and an upcoming meeting in Mexico on June 18 and 19 may revisit the issue.
Phasing out such subsidies was also originally on the agenda for the Rio+20 sustainability summit in Brazil from June 20-22 but agreement on the issue seems unlikely.
EU climate commissioner Connie Hedegaard told Reuters on Tuesday that the subsidy outcome in Rio would depend on discussions at the preceding G20 meeting.
Editing by Keiron Henderson