1. Hadley Centre for Climate Prediction and Research, Met Office, Bracknell, Berkshire RG12 2SY, UK
2. Space Science and Technology Department, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK

Correspondence to: Peter A. Stott¹ Correspondence and requests for materials should be addressed to P.A.S. (e-mail: Email: peter.stott@metoffice.com).

Abstract

Predictions of temperature rise over the twenty-first century are necessarily uncertain, both because the sensitivity of the climate system to changing atmospheric greenhouse-gas concentrations, as well as the rate of ocean heat uptake, is poorly quantified^{1, 2} and because future influences on climate—of anthropogenic as well as natural origin—are difficult to predict³. Past observations have been used to help constrain the range of uncertainties in future warming rates, but under the assumption of a particular scenario of future emissions⁴. Here we investigate the relative importance of the uncertainty in climate response to a particular emissions scenario versus the uncertainty caused by the differences between future emissions scenarios for our estimates of future change. We present probabilistic forecasts of global-mean temperatures for four representative scenarios for future emissions⁵, obtained with a comprehensive climate model. We find that, in the absence of policies to mitigate climate change, global-mean temperature rise is insensitive to the differences in the emissions scenarios over the next four decades. We also show that in the future, as the signal of climate change emerges further, the predictions will become better constrained.

1. Hadley Centre for Climate Prediction and Research, Met Office, Bracknell, Berkshire RG12 2SY, UK
2. Space Science and Technology Department, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK

Correspondence to: Peter A. Stott¹ Correspondence and requests for materials should be addressed to P.A.S. (e-mail: Email: peter.stott@metoffice.com).