Tropical cyclones and climate change

North Atlantic tropical cyclone activity according to the Power Dissipation Index, 1949–2015. Sea surface temperature has been plotted alongside the PDI to show how they compare. The lines have been smoothed using a five-year weighted average, plotted at the middle year.

Climate change can affect tropical cyclones in a variety of ways: an intensification of rainfall and wind speed, a decrease in overall frequency, an increase in the frequency of very intense storms and a poleward extension of where the cyclones reach maximum intensity are among the possible consequences of human-induced climate change.[1] Tropical cyclones use warm, moist air as their source of energy or "fuel". As climate change is warming ocean temperatures, there is potentially more of this fuel available.[2]

Between 1979 and 2017, there was a global increase in the proportion of tropical cyclones of Category 3 and higher on the Saffir–Simpson scale. The trend was most clear in the North Atlantic and in the Southern Indian Ocean. In the North Pacific, tropical cyclones have been moving poleward into colder waters and there was no increase in intensity over this period.[3] With 2 °C (3.6 °F) warming, a greater percentage (+13%) of tropical cyclones are expected to reach Category 4 and 5 strength.[1] A 2019 study indicates that climate change has been driving the observed trend of rapid intensification of tropical cyclones in the Atlantic basin. Rapidly intensifying cyclones are hard to forecast and therefore pose additional risk to coastal communities.[4]

Warmer air can hold more water vapor: the theoretical maximum water vapor content is given by the Clausius–Clapeyron relation, which yields ≈7% increase in water vapor in the atmosphere per 1 °C (1.8 °F) warming.[5][6] All models that were assessed in a 2019 review paper show a future increase of rainfall rates.[1] Additional sea level rise will increase storm surge levels.[7][8] It is plausible that extreme wind waves see an increase as a consequence of changes in tropical cyclones, further exacerbating storm surge dangers to coastal communities.[9] The compounding effects from floods, storm surge, and terrestrial flooding (rivers) are projected to increase due to global warming.[8]

There is currently no consensus on how climate change will affect the overall frequency of tropical cyclones.[1] A majority of climate models show a decreased frequency in future projections.[9] For instance, a 2020 paper comparing nine high-resolution climate models found robust decreases in frequency in the Southern Indian Ocean and the Southern Hemisphere more generally, while finding mixed signals for Northern Hemisphere tropical cyclones.[10] Observations have shown little change in the overall frequency of tropical cyclones worldwide,[11] with increased frequency in the North Atlantic and central Pacific, and significant decreases in the southern Indian Ocean and western North Pacific.[12] There has been a poleward expansion of the latitude at which the maximum intensity of tropical cyclones occurs, which may be associated with climate change.[13] In the North Pacific, there may also have been an eastward expansion.[7] Between 1949 and 2016, there was a slowdown in tropical cyclone translation speeds. It is unclear still to what extent this can be attributed to climate change: climate models do not all show this feature.[9]

  1. ^ a b c d Knutson, Thomas; Camargo, Suzana J.; Chan, Johnny C. L.; Emanuel, Kerry; Ho, Chang-Hoi; Kossin, James; Mohapatra, Mrutyunjay; Satoh, Masaki; Sugi, Masato; Walsh, Kevin; Wu, Liguang (August 6, 2019). "Tropical Cyclones and Climate Change Assessment: Part II. Projected Response to Anthropogenic Warming". Bulletin of the American Meteorological Society. 101 (3): BAMS–D–18–0194.1. Bibcode:2020BAMS..101E.303K. doi:10.1175/BAMS-D-18-0194.1.
  2. ^ "Major tropical cyclones have become '15% more likely' over past 40 years". Carbon Brief. May 18, 2020. Archived from the original on August 8, 2020. Retrieved August 31, 2020.
  3. ^ Kossin, James P.; Knapp, Kenneth R.; Olander, Timothy L.; Velden, Christopher S. (May 18, 2020). "Global increase in major tropical cyclone exceedance probability over the past four decades". Proceedings of the National Academy of Sciences. 117 (22): 11975–11980. Bibcode:2020PNAS..11711975K. doi:10.1073/pnas.1920849117. PMC 7275711. PMID 32424081.
  4. ^ Collins, M.; Sutherland, M.; Bouwer, L.; Cheong, S.-M.; et al. (2019). "Chapter 6: Extremes, Abrupt Changes and Managing Risks" (PDF). IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. p. 602. Archived (PDF) from the original on December 20, 2019. Retrieved October 6, 2020.
  5. ^ Knutson, Thomas R.; Sirutis, Joseph J.; Zhao, Ming; Tuleya, Robert E.; Bender, Morris; Vecchi, Gabriel A.; Villarini, Gabriele; Chavas, Daniel (15 September 2015). "Global Projections of Intense Tropical Cyclone Activity for the Late Twenty-First Century from Dynamical Downscaling of CMIP5/RCP4.5 Scenarios". Journal of Climate. 28 (18): 7203–7224. Bibcode:2015JCli...28.7203K. doi:10.1175/JCLI-D-15-0129.1. S2CID 129209836. Archived from the original on 5 January 2020. Retrieved 9 December 2019.
  6. ^ Knutson, Thomas R.; Sirutis, Joseph J.; Vecchi, Gabriel A.; Garner, Stephen; Zhao, Ming; Kim, Hyeong-Seog; Bender, Morris; Tuleya, Robert E.; Held, Isaac M.; Villarini, Gabriele (1 September 2013). "Dynamical Downscaling Projections of Twenty-First-Century Atlantic Hurricane Activity: CMIP3 and CMIP5 Model-Based Scenarios". Journal of Climate. 26 (17): 6591–6617. Bibcode:2013JCli...26.6591K. doi:10.1175/JCLI-D-12-00539.1. S2CID 129571840. Archived from the original on 22 September 2022. Retrieved 21 November 2022.
  7. ^ a b Collins, M.; Sutherland, M.; Bouwer, L.; Cheong, S.-M.; et al. (2019). "Chapter 6: Extremes, Abrupt Changes and Managing Risks" (PDF). IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. p. 603. Archived (PDF) from the original on December 20, 2019. Retrieved October 6, 2020.
  8. ^ a b "Hurricane Harvey shows how we underestimate flooding risks in coastal cities, scientists say". The Washington Post. August 29, 2017. Archived from the original on August 30, 2017. Retrieved August 30, 2017.
  9. ^ a b c Walsh, K. J. E.; Camargo, S. J.; Knutson, T. R.; Kossin, J.; Lee, T. -C.; Murakami, H.; Patricola, C. (December 1, 2019). "Tropical cyclones and climate change". Tropical Cyclone Research and Review. 8 (4): 240–250. Bibcode:2019TCRR....8..240W. doi:10.1016/j.tcrr.2020.01.004.
  10. ^ Roberts, Malcolm John; Camp, Joanne; Seddon, Jon; Vidale, Pier Luigi; Hodges, Kevin; Vannière, Benoît; Mecking, Jenny; Haarsma, Rein; Bellucci, Alessio; Scoccimarro, Enrico; Caron, Louis-Philippe (2020). "Projected Future Changes in Tropical Cyclones Using the CMIP6 HighResMIP Multimodel Ensemble". Geophysical Research Letters. 47 (14): e2020GL088662. Bibcode:2020GeoRL..4788662R. doi:10.1029/2020GL088662. PMC 7507130. PMID 32999514. S2CID 221972087.
  11. ^ "Hurricanes and Climate Change". Union of Concerned Scientists. Archived from the original on September 24, 2019. Retrieved September 29, 2019.
  12. ^ Murakami, Hiroyuki; Delworth, Thomas L.; Cooke, William F.; Zhao, Ming; Xiang, Baoqiang; Hsu, Pang-Chi (2020). "Detected climatic change in global distribution of tropical cyclones". Proceedings of the National Academy of Sciences. 117 (20): 10706–10714. Bibcode:2020PNAS..11710706M. doi:10.1073/pnas.1922500117. PMC 7245084. PMID 32366651.
  13. ^ James P. Kossin; Kerry A. Emanuel; Gabriel A. Vecchi (2014). "The poleward migration of the location of tropical cyclone maximum intensity". Nature. 509 (7500): 349–352. Bibcode:2014Natur.509..349K. doi:10.1038/nature13278. hdl:1721.1/91576. PMID 24828193. S2CID 4463311.

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