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Coral bleaching under unconventional scenarios of climate warming and ocean acidification


Elevated sea surface temperatures have been shown to cause mass coral bleaching1,2,3. Widespread bleaching, affecting >90% of global coral reefs and causing coral degradation, has been projected to occur by 2050 under all climate forcing pathways adopted by the IPCC for use within the Fifth Assessment Report4,5. These pathways include an extremely ambitious pathway aimed to limit global mean temperature rise to 2 °C (ref. 6; Representative Concentration Pathway 2.6—RCP2.6), which assumes full participation in emissions reductions by all countries, and even the possibility of negative emissions7. The conclusions drawn from this body of work, which applied widely used algorithms to estimate coral bleaching8, are that we must either accept that the loss of a large percentage of the world’s coral reefs is inevitable, or consider technological solutions to buy those reefs time until atmospheric CO2 concentrations can be reduced. Here we analyse the potential for geoengineering, through stratospheric aerosol-based solar radiation management (SRM), to reduce the extent of global coral bleaching relative to ambitious climate mitigation. Exploring the common criticism of geoengineering—that ocean acidification and its impacts will continue unabated—we focus on the sensitivity of results to the aragonite saturation state dependence of bleaching. We do not, however, address the additional detrimental impacts of ocean acidification on processes such as coral calcification9,10 that will further determine the benefit to corals of any SRM-based scenario. Despite the sensitivity of thermal bleaching thresholds to ocean acidification being uncertain11,12, stabilizing radiative forcing at 2020 levels through SRM reduces the risk of global bleaching relative to RCP2.6 under all acidification–bleaching relationships analysed.

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Figure 1: Scenarios of warming and ocean acidification.
Figure 2: Aragonite saturation state and bleaching thresholds.
Figure 3: DHM under RCP2.6 and RCP4.5 + SRM.
Figure 4: Annual coral bleaching under different Ωarag sensitivities.


  1. Brown, B. E. Coral bleaching: Causes and consequences. Coral Reefs 16, S129–S138 (1997).

    Article  Google Scholar 

  2. Edwards, A. J. et al. Coral bleaching and mortality on artificial and natural reefs in Maldives in 1998, sea surface temperature anomalies and initial recovery. Mar. Pollut. Bull. 42, 7–15 (2001).

    CAS  Article  Google Scholar 

  3. Hoegh-Guldberg, O. Climate change, coral bleaching and the future of the world’s coral reefs. Mar. Freshwat. Res. 50, 839–866 (1999).

    Article  Google Scholar 

  4. Frieler, K. et al. Limiting global warming to 2 °C is unlikely to save most coral reefs. Nature Clim. Change 3, 165–170 (2013).

    Article  Google Scholar 

  5. Van Hooidonk, R., Maynard, J. A. & Planes, S. Temporary refugia for coral reefs in a warming world. Nature Clim. Change 3, 508–511 (2013).

    CAS  Article  Google Scholar 

  6. Vuuren, D. et al. The representative concentration pathways: An overview. Climatic Change 109, 5–31 (2011).

    Article  Google Scholar 

  7. Jones, C. et al. Twenty-first-century compatible CO2 emissions and airborne fraction simulated by CMIP5 earth system models under four representative concentration pathways. J. Clim. 26, 4398–4413 (2013).

    Article  Google Scholar 

  8. Strong, A. E., Liu, G., Skirving, W. & Eakin, C. M. NOAA’s Coral Reef Watch program from satellite observations. Ann. GIS 17, 83–92 (2011).

    Article  Google Scholar 

  9. Langdon, C. & Atkinson, M. J. Effect of elevated p CO 2 on photosynthesis and calcification of corals and interactions with seasonal change in temperature/irradiance and nutrient enrichment. J. Geophys. Res. 110, C09S07 (2005).

    Article  Google Scholar 

  10. Chan, N. C. S. & Connolly, S. R. Sensitivity of coral calcification to ocean acidification: A meta-analysis. Glob. Change Biol. 19, 282–290 (2013).

    Article  Google Scholar 

  11. Anthony, K. R. N., Kline, D. I., Diaz-Pulido, G., Dove, S. & Hoegh-Guldberg, O. Ocean acidification causes bleaching and productivity loss in coral reef builders. Proc. Natl Acad. Sci. USA 105, 17442–17446 (2008).

    CAS  Article  Google Scholar 

  12. Wall, C. B., Fan, T-Y. & Edmunds, P. J. Ocean acidification has no effect on thermal bleaching in the coral Seriatopora caliendrum. Coral Reefs 33, 119–130 (2013).

    Article  Google Scholar 

  13. Moberg, F. & Folke, C. Ecological goods and services of coral reef ecosystems. Ecol. Econ. 29, 215–233 (1999).

    Article  Google Scholar 

  14. Enriquez, S., Mendez, E. R. & Iglesias-Prieto, R. Multiple scattering on coral skeletons enhances light absorption by symbiotic algae. Limnol. Oceanogr. 50, 1025–1032 (2005).

    Article  Google Scholar 

  15. Rasch, P. J. et al. An overview of geoengineering of climate using stratospheric sulphate aerosols. Phil. Trans. R. Soc. Math. A 366, 4007–4037 (2008).

    CAS  Article  Google Scholar 

  16. Kwiatkowski, L. et al. Caribbean coral growth influenced by anthropogenic aerosol emissions. Nature Geosci. 6, 362–366 (2013).

    CAS  Article  Google Scholar 

  17. Ricke, K. L., Orr, J. C., Schneider, K. & Caldeira, K. Risks to coral reefs from ocean carbonate chemistry changes in recent earth system model projections. Environ. Res. Lett. 8, 034003 (2013).

    Article  Google Scholar 

  18. Mumby, P. J. & van Woesik, R. Consequences of ecological, evolutionary and biogeochemical uncertainty for coral reef responses to climatic stress. Curr. Biol. 24, R413–R423 (2014).

    CAS  Article  Google Scholar 

  19. Collins, W. J. et al. Development and evaluation of an Earth-system model—HadGEM2. Geosci. Mod. Dev. Discuss. 4, 997–1062 (2011).

    Article  Google Scholar 

  20. Kravitz, B. et al. The geoengineering model intercomparison project (GeoMIP). Atmos. Sci. Lett. 12, 162–167 (2011).

    Article  Google Scholar 

  21. Ortiz, J. C., Bozec, Y-M., Wolff, N. H., Doropoulos, C. & Mumby, P. J. Global disparity in the ecological benefits of reducing carbon emissions for coral reefs. Nature Clim. Change 4, 1090–1094 (2014).

    Article  Google Scholar 

  22. Kwiatkowski, L., Halloran, P. R., Mumby, P. J. & Stephenson, D. B. What spatial scales are believable for climate model projections of sea surface temperature? Clim. Dynam. 43, 1483–1496 (2014).

    Article  Google Scholar 

  23. Donner, S. D. Coping with commitment: Projected thermal stress on coral reefs under different future scenarios. PLoS ONE 4, e5712 (2009).

    Article  Google Scholar 

  24. Couce, E., Irvine, P. J., Gregoire, L. J., Ridgwell, A. & Hendy, E. J. Tropical coral reef habitat in a geoengineered, high-CO2 world. Geophys. Res. Lett. 40, 1799–1805 (2013).

    Article  Google Scholar 

  25. Kennedy, E. V. et al. Avoiding coral reef functional collapse requires local and global action. Curr. Biol. 23, 912–918 (2013).

    CAS  Article  Google Scholar 

  26. Silverman, J., Lazar, B., Cao, L., Caldeira, K. & Erez, J. Coral reefs may start dissolving when atmospheric CO2 doubles. Geophys. Res. Lett. 36, L05606 (2009).

    Article  Google Scholar 

  27. McCulloch, M., Falter, J., Trotter, J. & Montagna, P. Coral resilience to ocean acidification and global warming through pH up-regulation. Nature Clim. Change 2, 623–627 (2012).

    CAS  Article  Google Scholar 

  28. Cao, L., Zhang, H., Zheng, M. & Wang, S. Response of ocean acidification to a gradual increase and decrease of atmospheric CO2 . Environ. Res. Lett. 9, 024012 (2014).

    Article  Google Scholar 

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We thank J. Orr, D. Long and I. Chollett for assistance with data processing. The study was financially supported by a NERC grant to P.J.M. and P.C., the University of Exeter, and the EU FORCE project and was supported by the Joint DECC/Defra Met Office Hadley Centre Climate Programme.

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L.K., P.C. and P.R.H. designed and conducted the research and analysis. A.J.W. and P.R.H. performed the HadGEM2-ES simulations. L.K., P.C., P.R.H., A.J.W. and P.J.M. wrote the paper.

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Correspondence to Lester Kwiatkowski.

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The authors declare no competing financial interests.

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Kwiatkowski, L., Cox, P., Halloran, P. et al. Coral bleaching under unconventional scenarios of climate warming and ocean acidification. Nature Clim Change 5, 777–781 (2015).

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