Tropical cyclones and climate change
Climate change affect tropical cyclones in a variety of ways: an intensification of rainfall and wind speed, an increase in the frequency of very intense storms and a poleward extension of where the cyclones reach maximum intensity are among the consequences of human-induced climate change.[1][2] 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.[3]
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.[4] 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.[5]
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.[6][7] 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.[8][9] 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.[10] The compounding effects from floods, storm surge, and terrestrial flooding (rivers) are projected to increase due to global warming.[9]
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.[10] 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.[11] Observations have shown little change in the overall frequency of tropical cyclones worldwide,[12] with increased frequency in the North Atlantic and central Pacific, and significant decreases in the southern Indian Ocean and western North Pacific.[13] 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.[14] In the North Pacific, there may also have been an eastward expansion.[8] 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.[10]
Media and public perception[edit]
The destruction from early 21st century Atlantic Ocean hurricanes, such as Hurricanes Katrina, Wilma, and Sandy, caused a substantial upsurge in interest in the subject of climate change and hurricanes by news media and the wider public, and concerns that global climatic change may have played a significant role in those events. In 2005 and 2017, related polling of populations affected by hurricanes concluded in 2005 that 39 percent of Americans believed climate change helped to fuel the intensity of hurricanes, rising to 55 percent in September 2017.[69]
After Typhoon Meranti in 2016, risk perception in China was not measured to increase. However, there was a clear rise in support for personal and community action against climate change.[70] In Taiwan, people that had lived through a typhoon did not express more anxiety about climate change. The survey did find a positive correlation between anxiety about typhoons and anxiety about climate change.[71]