Hurricane Matthew leaves around 900 dead in Haiti and 20 in the U.S. (as of October 10) [1]. Matthew is no longer a hurricane since October 9, but still involves hurricane-force winds and a threat of flooding. Now Matthew becomes an infamous name in the area. Unlike other natural disasters, hurricanes (or typhoons, or cyclones depending on where you live), or more broadly tropical cyclones, have their own name. Once a tropical cyclone occurs, it can last for several days so that there could be two or three tropical cyclones in the same region. In order to avoid confusion and to streamline communication, scientists prepared lists of cyclone names and are using them in constant rotation [2], however, in case of so deadly or damaging tropical cyclones, the name can be retired from the lists as Katrina in 2015 was [3], and Matthew this year will likely be.

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Snapshot from NASA’s “GPM Captures Hurricane Matthew Over Haiti

The tropical cyclones are generated in the tropics (no surprise!) since the regions can offer warm ocean waters, sufficient moisture, and the Coriolis force (a spin by the earth rotation) to the cyclones. Then, has global warming affected the behaviours of tropical cyclones by warming up the tropical ocean waters? The best answer at present would be “there will be an increase in tropical cyclone intensity as the climate gets warmer, but we are not sure about its frequency yet”. Some modeling studies indicate that global warming may increase tropical cyclone activity by increasing available energy potential [4]. On the contrary, others argue that tropical cyclone frequency will either remain unchanged or even decrease, because the vertical wind shear (a difference in wind speed/direction with a change in altitude) is projected to increase due to global warming, which hinders tropical disturbances from growing strongly enough to be tropical cyclones [5]. But regardless of the frequency of tropical cyclones, both sides agree that their intensity will increase in a warmer world.

Will we ever be able to control tropical cyclones? There have been some ideas to prevent cyclones, such as mixing ocean waters to cool them down or nuking cyclones [6]. However, keep it mind that tropical cyclones are natural phenomena in terms of earth energy circulations. They transfer latent heat energy from the ocean to the atmosphere and carry thermal energy away from the tropics into mid-latitudes. Nobody can say for certain what will happen by intervening in the energy circulation of the earth. Thus I would vote for more investments on weather observations, forecasting, mitigation and adaptation rather than manipulating the earth system with high risk of unforeseen consequences [7][8][9].


 

Sources

[1] Hurricane Matthew slams into South Carolina as Haiti death toll nears 900, The Telegraph, Oct 8, 2016
[2] Tropical Cyclone Naming History and Retired Names, NOAA
[3] Retired Atlantic Hurricane Names, Weather Underground
[4] Global Warming and Hurricanes, GFDL, NOAA
[5] Large-scale Climate Projections and Hurricanes, GFDL, NOAA
[6] Tropical cyclone modification and myths, Hurricane Research Division, NOAA
[7] Can Bill Gates stop hurricanes? Scientists doubt it, CNN, Sep 1, 2009
[8] Why can’t we stop a hurricane before it hits us?, Popular Science
[9] Can we control hurricanes?, AtmosNews, UCAR

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