World leaders at a climate conference last year in Cancun, Mexico, agreed that long-term concentration of greenhouse gas emissions should be limited to roughly 450 parts per million of carbon dioxide equivalent to limit expected temperature increases.
The International Energy Agency announced that emissions have increased by 5 percent from 2008 levels.
"Our latest estimates are another wake-up call," said IEA economist Fatih Birol in a statement. "Given the shrinking room for maneuver in 2020, unless bold and decisive decisions are made very soon, it will be extremely challenging to succeed in achieving this global goal agreed in Cancun."
The IEA said energy-related CO2 emissions in 2010 were the highest recorded. At least 80 percent of the projected emissions from the energy sector in 2020 are on the books because of current or future construction plans.
Birol said the latest figures represent a "serious setback" in the effort to keep global temperature fluctuations in check.