The international economic recession has led to the steepest drop in greenhouse gas emissions in 40 years, according to a new study by the International Energy Agency. Emissions fell by approximately 2.6 percent, an ‘unprecedented’ decline that the IEA highlights as a chance to get a leg up on the fight against climate change.

Falling industrial output is the biggest factor in the drop, but carbon trading schemes and lack of financing for new coal-fired power plants have also played a role. Europe’s target to cut emissions by 20 percent by 2020, China’s energy efficiency policies and U.S. car emission standards are cited as having a particularly notable effect.

This year’s decline in emissions will well exceed the 1.3 percent drop that followed the oil crisis in 1981.

The new data will play a role in discussions among world leaders at the climate change conference in Copenhagen this December, as they attempt to agree upon a new climate pact to replace the Kyoto Protocol for 2012. 

The IEA figures also come as leaders prepare to gather in New York Tuesday for a one-day climate change summit held by Ban Ki-moon, secretary general of the United Nations.

Fatih Birol, IEA chief economist, called the drop “surprising” and predicts that it will make efforts to achieve the emissions reductions that experts say are necessary to combat global warming “much less difficult”.

However, he noted that the fall in emissions will only be meaningful with an agreement in Copenhagen that provides a low-carbon signal to investors.

“We hope that an agreement in Copenhagen would give a signal for new investments to go in [an environmentally] sustainable direction. If we miss this opportunity it will be much more expensive and harder than ever to bring the world’s energy system onto a sustainable path,” Birol told The Financial Times.