Non-CO2 greenhouse gases and climate change

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Earth’s climate is warming as a result of anthropogenic emissions of greenhouse gases, particularly carbon dioxide (CO2) from fossil fuel combustion. Anthropogenic emissions of non-CO2 greenhouse gases, such as methane, nitrous oxide and ozone-depleting substances (largely from sources other than fossil fuels), also contribute significantly to warming. Some non-CO2 greenhouse gases have much shorter lifetimes than CO2, so reducing their emissions offers an additional opportunity to lessen future climate change. Although it is clear that sustainably reducing the warming influence of greenhouse gases will be possible only with substantial cuts in emissions of CO2, reducing non-CO2 greenhouse gas emissions would be a relatively quick way of contributing to this goal.

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Figure 1: Anthropogenic emissions of non-CO2 GHGs and CO2.
Figure 2: Annual anthropogenic emissions of non-CO2 GHGs in recent years1,9,10,17,18,56.
Figure 3: Direct radiative forcing derived from observed and projected abundances of LLGHGs33.
Figure 4: Relative changes in radiative forcing from a 25% cut in GHG emissions.


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We acknowledge discussions with P. Tans and J. Daniel, updates to data published in ref. 33 from J. Elkins, G. Dutton and T. Conway, and technical assistance from C. Siso and B. Miller. This work was supported in part by the Atmospheric Composition and Climate Program and the Carbon Cycle Program of NOAA’s Climate Program Office.

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The writing and drafting of figures was led by S.A.M., but all three authors contributed to the writing and to the ideas presented in this review.

Correspondence to S. A. Montzka.

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