Plans published by rich nations and major emerging countries to cut greenhouse gas emissions are not enough to limit a rise in global temperatures to 2 degrees Celsius (3.6 Fahrenheit), the Organisation for Economic Cooperation and Development said on Tuesday.

The United Nations has set that increase in average temperature from pre-industrial levels as the ceiling to avert dramatic increases in heatwaves, droughts, floods and extinctions.

But a report from the Paris-based think-tank analysed the past efforts and new pledges of its 34 members and 10 other partner countries including China and India, which together account for more than 80 percent of global carbon emissions.

"Countries have made efforts but these are not sufficient to reach their own targets, let alone reach the 2 degrees Celsius objective," climate specialist Mikaela Rambali, who co-authored the report, told reporters in Paris.

The study coincides with Monday's start of a week of talks among almost 200 nations in Bonn, Germany, the final preparatory session before a a U.N. climate summit in Paris in December intended to produce an agreement to limit climate change beyond 2020.

About 150 nations have so far submitted national plans for fighting climate change as building blocks of a Paris accord. But there is no agreed system to compare each nation's level of ambition. – Reuters