Higher CO₂ concentrations increase extreme event risk in a 1.5 °C world

Journal Article · 10 June 2018 · Nature Climate Change

DOI: https://doi.org/10.1038/s41558-018-0190-1 · OSTI ID:1543757

Baker, Hugh S.  ^[1]; Millar, Richard J. ^[1]; Karoly, David J. ^[2]; Beyerle, Urs ^[3]; Guillod, Benoit P.  ^[4]; Mitchell, Dann ^[5]; Shiogama, Hideo  ^[6]; Sparrow, Sarah  ^[1]; Woollings, Tim ^[1]; Allen, Myles R. ^[1]

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1. Univ. of Oxford (United Kingdom)
2. Univ. of Oxford (United Kingdom); Univ. of Melbourne (Australia); Australian Research Council Centre of Excellence for Climate System Science, Melbourne, VIC (Australia)
3. Swiss Federal Inst. of Technology, Zurich (Switzerland)
4. Univ. of Oxford (United Kingdom); Swiss Federal Inst. of Technology, Zurich (Switzerland)
5. Univ. of Bristol (United Kingdom)
6. National Inst. for Environmental Studies, Tsukuba (Japan)

The Paris Agreement aims to ‘pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels.’ However, it has been suggested that temperature targets alone are insufficient to limit the risks associated with anthropogenic emissions. Here, using an ensemble of model simulations, we show that atmospheric CO₂ increase—an even more predictable consequence of emissions than global temperature increase—has a significant direct impact on Northern Hemisphere summer temperature, heat stress, and tropical precipitation extremes. Hence in an iterative climate mitigation regime aiming solely for a specific temperature goal, an unexpectedly low climate response may have corresponding ‘dangerous’ changes in extreme events. The direct impact of higher CO₂ concentrations on climate extremes therefore substantially reduces the upper bound of the carbon budget, and highlights the need to explicitly limit atmospheric CO2 concentration when formulating allowable emissions. Thus, complementing global mean temperature goals with explicit limits on atmospheric CO₂ concentrations in future climate policy would limit the adverse effects of high-impact weather extremes.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Univ. of California, Oakland, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1543757
• Journal Information: Nature Climate Change, Journal Name: Nature Climate Change Journal Issue: 7 Vol. 8; ISSN 1758-678X
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United States
• Language: English