Hurricanes and Climate Change
QUICK FACTS FOR ANY STORY
Evidence continues to mount that human-induced climate change is causing hurricanes to grow stronger and more destructive. Hurricanes are producing heavier rain, their storm surges are riding atop higher sea levels, and in many cases they are lingering longer over land, causing increased flooding and infrastructure destruction.
- The five costliest U.S. Earth-system disasters (including earthquakes, volcanic eruptions, fires, and all kinds of extreme weather) have all been hurricanes, and all five have occurred within the past 15 years: Harvey (2017), Katrina (2005), Sandy (2012), Irma (2017), and Maria (2017). 1
- Hurricanes get their energy from ocean heat; the warmer the water is, the stronger a hurricane can get. More than 90% of the excess heat trapped in the climate system due to human-caused global warming has gone into the oceans, providing the added energy driving recent hurricanes’ extreme wind intensities and the increased evaporation that has resulted in associated torrential rainfall. 2
- Globally, the last few decades have seen a growing proportion of strong hurricanes and a corresponding shrinking proportion of weak ones. Specifically, from 1975 to 2010, the proportion of Category 4 or 5 hurricanes (the highest wind speeds) increased by 25-30 percent for every 1 degree Celsius increase in global temperature due to human causes, resulting in a near doubling of the proportion of those most intense hurricanes. 3
- Both heavy rain and storm surge—water pushed ashore by heavy winds—contribute to flooding, which causes the vast majority of hurricane-related deaths and financial losses. The amount of rain falling in recent hurricanes has increased due to climate change, including in Harvey (by 20 to 38 percent), 4,5 Katrina, Irma, and Maria. 6 Hurricanes are also producing higher storm surges due to sea level rise. 7
- Climate-change-related perturbations in atmospheric winds like the jet stream may be contributing to a trend in which hurricanes are moving more slowly over the United States 8 (slowing by 17% over the past century), 9 and are increasingly likely to “stall” near the coast, potentially leading to catastrophic local rainfall and flooding. 10
- There has been a significant increase in how quickly hurricanes intensify in the Atlantic basin in recent decades, an expected symptom of global warming. 11 Hurricanes that intensify rapidly are difficult to forecast accurately and prepare for, especially when this occurs close to the coast, and cause a disproportionate amount of human and financial losses. 12
- Globally, hurricanes are reaching their maximum intensities further from the tropics, shifting toward temperate, heavily populated coastal regions that have not historically experienced them. Northern Hemisphere hurricane peak intensities have shifted northward by 100 miles in the past 30 years. 13
Pitfalls to Avoid
Avoid asking whether climate change “caused” a particular hurricane to slow, intensify rapidly, etc., as there are always many contributors to any weather event. Instead, ask whether climate change contributed to the intensity of a hurricane or the likelihood of its especially damaging behavior (such as stalling over a coastline)—questions that scientists can increasingly answer with confidence given recent advances in attribution science.
Dr. James Kossin (National Oceanic and Atmospheric Administration, National Centers for Environmental Information) email@example.com
Dr. Suzana Camargo (Columbia University) firstname.lastname@example.org
Dr. Jeff Masters (Weather Underground) email@example.com
1. NOAA Office for Coastal Management: Hurricane Costs 2. IPCC, 2014, Synthesis Report, Summary for Policymakers, p. 4. 3. Holland, G. et al., (2014), Climate Dynamics, 42, 617. 4. Risser, M. D., et al., (2017), Attributable human-induced changes in the likelihood and magnitude of the observed extreme precipitation during hurricane Harvey, Geophys. Res. Lett., 44, 12457–12464, and Wang, S. Y. et al., (2018) 5. Wang et al., Quantitative attribution of climate effects on Hurricane Harvey’s extreme rainfall in Texas, Env. Res. Lett., 13, 054014. 6. Patricola, C. and Wehner, M., (2018), Anthropogenic influences on major tropical cyclone events, Nature, 563, 339–346. 7. Rahmstorf, S., (2017), Rising hazard of storm-surge flooding, PNAS, 114 (45), 11806-11808 8. Kossin, J. P., (2018), A global slowdown of tropical-cyclone translation speed, Nature, 558 (7708), 104 9. Kossin, J. P., (2019), Matters Arising, Reply to Moon et al. and Lanzante, J.R.. Nature, 570, E16-E22. 10. Hall, T. M. and Kossin, J. P., (2019), Hurricane stalling along the North American coast and implications for rainfall, Climate and Atmospheric Science. 11. Bhatia et al., (2019), Recent increases in tropical cyclone intensification rates, Nature Communications, 10, 635. 12. Emanuel, K., (2017), Will global warming make hurricane forecasting more difficult?, Bulletin of the American Meteorological Society, 98, 495-501. 13. Kossin, J. P., et al., (2014), The poleward migration of the location of tropical cyclone maximum intensity. Nature, 509, 349-352.
Last Updated August 28, 2019
This tip sheet for reporters is one in a series produced jointly by two philanthropically supported, editorially independent services for journalists: SciLine, based at the American Association for the Advancement of Science (AAAS), and Climate Communication.