LONDON, (Reuters) - Mexico and Argentina are leading  a shift to make the global economy more climate friendly,  according to an index of “carbon competitiveness”, the  London-based thinktank E3G said yesterday.

G20 leaders meet at a summit on Sept 24-25 in Pittsburgh to help steer the global economy out of recession, and will also  discuss ways to finance the fight against climate change.

Long-term policies to limit climate change are widely expected to force nations to cut greenhouse gas emissions,  favouring leaner, more efficient economies run on renewable and  other low-carbon energy supplies.

“Countries that adapt quickly to a carbon-constrained world will be better able to deliver lasting prosperity for their  citizens,” said the E3G report, “G20 Low Carbon  Competitiveness”.

“There is a growing global consensus that our best path  toward strong economic recovery is through transitioning to a  less vulnerable, low carbon economy,” said Nick Mabey, E3G chief  executive.

E3G measured national wealth per unit of carbon emissions to  find out which countries would be most competitive under carbon  limits.

France, Japan and Britain ranked top among the G20 nations,  according to E3G’s “carbon competitiveness index” — reflecting  France’s dependence on low-carbon nuclear power, Britain’s on  low-carbon gas, and Japan’s energy efficiency and nuclear power.

But only Mexico and Argentina were improving their output  per unit of carbon in line with national emissions trajectories  which would avoid dangerous climate change — while China came  top of all the other G20 under-performers — the report found.

The required trends in carbon emissions were taken from  calculations by the U.N.’s Intergovernmental Panel on Climate  Change (IPCC), E3G said.

Analysts say global recovery spending can link to the fight  against climate change, through the creation of “green collar”  jobs. For example an ailing autos industry is now restructuring  to supply more energy efficient and electric cars.