page_title: Tropical cyclones and climate change
section_title: Observed trends
hierarchical_section_title: Tropical cyclones and climate change / Observed trends
caption_attribution_description: English: global ocean heat content
context_page_description: Tropical cyclones and climate change concerns how tropical cyclones have changed, and are expected to further change due to climate change. The topic receives considerable attention from climate scientists who study the connections between storms and climate, and notably since 2005 makes news during active storm seasons. The 2018 U.S. National Climate Change Assessment reported that "increases in greenhouse gases and decreases in air pollution have contributed to increases in Atlantic hurricane activity since 1970."
  A hurricane occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a cyclone occurs in the south Pacific or Indian Ocean. Fundamentally, they are all the same type of storm. The inclusive term used by the scientific community is tropical cyclones.
context_section_description: The 2018 U.S. National Climate Change Assessment reports as a "key message" that "Increases in greenhouse gases and decreases in air pollution have contributed to increases in Atlantic hurricane activity since 1970."
  A 2010 review of related sciences found substantial uptake in the frequency of the most intense tropical cyclones, and increases in rainfall rates within 100 km of the storm centre of up to 20%.
  A tropical cyclone's rainfall is primarily controlled by its actual environmental sea surface temperature (SST) - relative to the tropical mean SST, called the relative sea surface temperature. The relative SST has also been identified to more precisely explain variations in Atlantic hurricane frequency, than absolute SST and tropical convection. The relative SST is defined as the SST in the TC environment minus the tropical (30°S-30°N) mean SST. Rainfall will expand outwards as the relative SST increases, associated with an expansion of a storm wind field. The largest tropical cyclones are observed in the western North Pacific tropics, where the largest values of relative SST and mid-tropospheric relative humidity are located. Flooding by TCs with global warming is projected primarily by increases in rainfall rate, rather than area extent.
caption: Global Heat Content (0–700 meters) layer.
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