The decline comes as political leaders are struggling to come up with a common approach to dealing with climate change.
The main factor behind this year’s drop in emissions is the slowdown in industrial activity and trade around the world, according to a study due to be released in November by the International Energy Agency.
But the energy agency, which provides policy advice and research to industrialized nations, found that government actions had also contributed to the drop in emissions. The agency said it expected to see global carbon emissions fall 2.6 percent this year.
The projected decline was first reported Monday by The Financial Times.
World leaders will meet at the United Nations on Tuesday for a one-day summit meeting to pursue a new agreement to fight global warming. The talks are expected to conclude with a climate treaty in Copenhagen in December.
The negotiations are stalled amid disagreements between developed and developing countries on how to share reductions in carbon emissions.
Even if temporary, a global reduction in emissions could allow advocates of stringent new limits on carbon dioxide to argue that continued progress is available using existing technology and switching to cleaner fuels, like natural gas.
The forecast should also make it easier for most nations to meet emissions reduction targets in the near and medium term and could give a lift toward a new global warming treaty, said Paul W. Bledsoe of the National Commission on Energy Policy, a bipartisan advisory group.
“Because many countries are using 2005 as a baseline year, this will give them some breathing room when economic activity picks up again,” Mr. Bledsoe said.
The projection from the International Energy Agency tracks other forecasts from government agencies, including the Department of Energy, which found that greenhouse gas emissions in the United States fell 3.8 percent in 2008 compared with 2007; they are estimated to be down another 6 percent this year.
However, an improving economy is expected to increase domestic carbon dioxide emissions 0.7 percent next year, according to the Energy Information Administration, an arm of the Department of Energy.
Carbon dioxide emissions from the burning of energy sources account for 80 percent of greenhouse gas emissions in the United States.