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2012 Global Carbon Emissions

It has been a year of climate-related records - we've seen exceptional heat, devastating drought, and the widespread melt of Arcitc sea ice. Now, as 2012 draws to a close, there's at least one more record to include in that list. Human-generated emissions of carbon dioxide (CO2) this year are expected to reach 35.6 billion tons. That’s up 2.6 percent from what was emitted in 2011, the previous record holder.

This extra gas will cause global temperatures to rise, as it traps solar heat from reflecting back out into space. But exactly how do those thirty-five billion tons relate to climbing temperatures?

This estimate, published this week in Nature Climate Change, is based on economic factors, such as changes to the global GDP, and technological factors, such as improvements in emissions intensity, which predict how many fossil fuels we’re burning, and how efficiently we’re doing it. For a full discussion of the report, click here.

The publication coincided with a report from the World Meteorological Organization (WMO) last week, which officially announced that atmospheric concentrations of CO2 reached a record 390.9 parts per million (ppm) in 2011. That concentration is 40 percent greater than what is was in 1750, before humans started burning fossil fuels in earnest. The concentrations of other greenhouse gases, such as methane and nitrous oxide, also reached record amounts. According to the Global Carbon Project, levels of atmospheric CO2 haven’t been this high since at least 800,000 years ago. Thanks to this, we’re now trapping about 30 percent more solar heat every year than we were 250 years ago.

Thirty-five billion tons a year of CO2 is about 58 percent more than what the world emitted in 1990 – the year the United Nations uses as a baseline for its discussions of how to reduce global emissions. During the 2009 U.N. climate negotiations, countries agreed to keep temperatures from rising more than 2°C (3.6°F) by 2100. However, as emissions have continued to rise, many scientists worry that 2°C of warming by the end of this century may be inevitable.

Projections from the IPCC and the World Bank argue that we could see as much as 4°C (7.2°F) by 2100. According to those projections, we are “virtually certain” to exceed the 2°C target with the current level of cuts pledged by various countries, and have a 50 percent chance of reaching 3°C (4.2°F).

These figures come as U.N. representatives meet this week in Doha, Qatar for the latest round of climate change negotiations.