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Impact of delay in reducing carbon dioxide emissions


Recent downward revisions in the climate response to rising CO2 levels, and opportunities for reducing non-CO2 climate warming, have both been cited as evidence that the case for reducing CO2 emissions is less urgent than previously thought. Evaluating the impact of delay is complicated by the fact that CO2 emissions accumulate over time, so what happens after they peak is as relevant for long-term warming as the size and timing of the peak itself. Previous discussions have focused on how the rate of reduction required to meet any given temperature target rises asymptotically the later the emissions peak. Here we focus on a complementary question: how fast is peak CO2-induced warming increasing while mitigation is delayed, assuming no increase in rates of reduction after the emissions peak? We show that this peak-committed warming is increasing at the same rate as cumulative CO2 emissions, about 2% per year, much faster than observed warming, independent of the climate response.

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Figure 1: Schematic emission scenarios illustrating the impact of different estimates of the climate system response to CO2 emissions.


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M.R.A. acknowledges support from the UK Department of Energy and Climate Change under contract TRN 317/11/2011 and from the Oxford Martin School.

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Correspondence to Myles R. Allen.

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Allen, M., Stocker, T. Impact of delay in reducing carbon dioxide emissions. Nature Clim Change 4, 23–26 (2014).

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