Limiting global warming to 2 °C is unlikely to save most coral reefs

• Published in: Nature climate change 2012-09, Vol.3 (2), p.165-170
• Main Authors: Frieler, K., Meinshausen, M., Golly, A., Mengel, M., Lebek, K., Donner, S. D., Hoegh-Guldberg, O.
• Format: Article
• Language: English
• Subjects: 704/106/694; 704/106/829; 704/158/2446/837; 704/158/672; Acidification; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Climate Change; Climate Change/Climate Change Impacts; Climatology. Bioclimatology. Climate change; Conservation, protection and management of environment and wildlife; Coral bleaching; Coral reefs; Earth and Environmental Science; Earth, ocean, space; Emissions; Environment; Environmental degradation: ecosystems survey and restoration; Environmental Law/Policy/Ecojustice; Exact sciences and technology; External geophysics; Fundamental and applied biological sciences. Psychology; General circulation models; Global temperatures; Global warming; Intergovernmental Panel on Climate Change; Meteorology; Mortality; Ocean acidification; Ocean temperature; Temperature; Thermal stress
• ISSN: 1758-678X; 1758-6798
• DOI: 10.1038/nclimate1674

Mass coral bleaching events have become a widespread phenomenon causing serious concerns with regard to the survival of corals. Triggered by high ocean temperatures, bleaching events are projected to increase in frequency and intensity. Here, we provide a comprehensive global study of coral bleaching in terms of global mean temperature change, based on an extended set of emissions scenarios and models. We show that preserving >10% of coral reefs worldwide would require limiting warming to below 1.5 °C (atmosphere–ocean general circulation models (AOGCMs) range: 1.3–1.8 °C) relative to pre-industrial levels. Even under optimistic assumptions regarding corals’ thermal adaptation, one-third (9–60%, 68% uncertainty range) of the world’s coral reefs are projected to be subject to long-term degradation under the most optimistic new IPCC emissions scenario, RCP3-PD. Under RCP4.5 this fraction increases to two-thirds (30–88%, 68% uncertainty range). Possible effects of ocean acidification reducing thermal tolerance are assessed within a sensitivity experiment. Comprehensive computer simulations show that coral reefs are likely to suffer extensive long-term degradation resulting from mass bleaching events even if the expected increase in global mean temperature can be kept well below 2 °C. Without major mitigation efforts to limit global warming significantly, the fate of coral reef ecosystems seems to be sealed.