Study shows CO2 causes global warming faster than feared

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New research suggests that it takes just 10 years for CO2 emissions to have maximum effect (Image: NASA)

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Any given CO2 emission will have its maximum warming effect just 10 years later, new research from the Carnegie Institution for Science shows. The Institute of Physics (IOP) says this research, published in full on the web today, has "dispelled a common misconception" that the warming effects of CO2 emissions aren't felt for decades.

"Our results show that people alive today are very likely to benefit from emissions avoided today, and that these will not accrue solely to impact future generations," says lead researcher Dr. Katharine Ricke. "Our findings should dislodge previous misconceptions about this timeframe that have played a key part in the failure to reach policy consensus."

The key findings of the research are:

  • that a single CO2 emission has its maximum effect on the Earth an average of 10 years after being emitted
  • that this also means the benefits of reducing CO2 emissions will also be felt sooner rather than later, which the IOP suggests could help avoid droughts, heatwaves and floods
  • that warming effects "can persist for more than a century"

The research looked at the results from two climate modelling projects: one on the time it takes for the ocean and biosphere to take up "a large pulse" of atmospheric CO2; and one on the Earth's climate system, also used by the Intergovernmental Panel on Climate Change in its latest assessment.

The precise figure, actually 10.1 years, is the median time for an emission to take maximum effect. According to the research there's a 90-percent chance of that maximum effect to occur between 6.6 and 30.7 years of the original emission.

This 10-year lag is due to the fact that it takes longer for the upper layers of the ocean to heat up than the atmosphere – it's ocean temperatures which cause the climate to change overall.

If there's a silver lining it's that this also means the benefits of reducing CO2 emissions will also be felt sooner rather than later, which the IOP suggests could help avoid droughts, heatwaves and floods.

The researchers say there is "substantial uncertainty" about the extent and duration of the warming due to uncertainties around climate sensitivity, carbon cycle and thermal inertia of the climate system.

"All three uncertainty factors contribute substantially to the total uncertainty about the timing of the maximum warming associated with a present day emission," Ricke tells Gizmag. "The analysis we did, which is based on results from the best climate and carbon cycle models available, indicates that the best guess according to the state of the science for time until emissions maximum effect is only a decade – considerably shorter than the best guess scientists seemed to be making before.

"But in order to substantially narrow this 90 percent 'very likely' range of 6 to 30 years until maximum warming, we need to work to improve our understanding of all uncertain components of these estimates, not just climate sensitivity."

According to Ricke, this is the first research into how long it takes for a single CO2 emission to take effect. The paper, published in the IOP's Environmental Research Letters is freely available to read online.

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