Wednesday, 7 September 2016

Number of strong tropical storms has doubled

New Study: Climate Change Has Doubled the Number of Category 4 and 5 Storms Striking East and Southeast Asia


6 September, 2016

The atmospheric-ocean heat engine. It’s a pretty simple mechanism for pumping up the power of storms. But as simple as it is, the results can be devastating when this engine gets revved up by human-forced climate change, according to a new study released Monday in Nature Geoscience.

The Heat Engine in Action

As the ocean surface warms, it heats the local atmosphere. This generates an updraft that pushes higher and higher into the air above. Heat also causes water at the ocean surface to evaporate. This evaporated water is borne up on the winds and air currents rising above the heating water. A low-pressure system forms and the water vapor condenses into clouds which ultimately become thunderstorms. The Coriolis effect gives it all a nudge and the storms and clouds start to pin…

pacific_typhoon_tracks_1980-2005
(Pacific Ocean typhoon paths from 1980 through 2005. A new study shows that the destructive power of landfalling typhoons in East and Southeast Asia has increased by nearly 50 percent since 1977. Meanwhile, the number of category 4 and 5 storms striking land has doubled. All impacts due to ocean-surface warming related to human-caused climate change. Image source: Commons.)

The process described above happens every day at the ocean surface. Sometimes these storms form into the powerful cyclones we call hurricanes and typhoons. Under normal global temperature conditions, the kinds and intensities of these storms are what we have generally come to expect. But if you add heat to the Earth System, as we do when we burn fossil fuels and dump carbon into the atmosphere, the whole storm formation process gets amped up — and produces the powerful outlier storms that have become more common over recent years.
Add Human-Forced Warming and End up With More Powerful Storms
The fact that such added heat tends to generate more powerful storms has been a generally accepted part of our understanding of climate science for some time now. However, it was not until recently that this signal of rising storm intensity became visible in the science. Now, a new study published today in Nature Geoscience indicates that’s exactly what’s happening in parts of the Western Pacific.

It’s a pretty earth-shattering revelation with multiple climate change-related findings which are worth reading about in full here. These findings boil down to the following:
  1. The number of category 4 and 5 storms striking southeast Asia has doubled since 1977.
  2. The overall destructive power of storms striking this region has increased by nearly 50 percent over the same period.
  3. This increase in powerful storms has been caused by ocean warming related to climate change.
Standing alone, any one of these findings would be significant. Taken together, they paint a picture of significantly rising risk of storm damage and related loss of life due to climate change in one of the world’s most highly populated regions. In other words, the storms firing and running in to land in this region are not the same as they once were. They have been dramatically altered by the massive volume of greenhouse gasses hitting the world’s atmosphere due to fossil-fuel burning, accumulating over the decades.
The study notes that:
Here, we apply analysis to corrected data and show that, over the past 37 years, typhoons that strike East and Southeast Asia have intensified by 12 to 15 percent… a nearly 50 percent increase in instantaneous destructiveness… with the proportion of category 4 and 5 storms doubling or even tripling… We find that increasing intensity of landfalling typhoons is due to strengthened intensification rates which are, in turn, tied to locally enhanced surface warming on the rim of East and Southeast Asia.
Ramping Storm Intensity
This scientific study helps validate and clarify what many weather and climate observers have already noted during recent years. The destructiveness of storms striking land in East and Southeast Asia is not normal. And, land-falling category 4 and 5 storms are occurring with greater frequency over broader regions.
4-storms-take-aim-on-southeast-asia
(Four Pacific typhoons take aim on Southeast Asia during July of 2015. A new study finds that the landfall intensity of storms like these is increasing due to human-caused climate change. Image source: NOAA.)

The Western Pacific basin is now capable of producing storms like Haiyan, whose destructive intensity at landfall was mostly theoretical decades before. This increase in intensity has been observed during a period of rapid Earth warming. And with more warming in store, the storms are likely to grow even more intense. From the Nature Geoscience study:
The projected ocean surface warming pattern under increased greenhouse gas forcing suggests that typhoons striking eastern mainland China, Taiwan, Korea, and Japan will intensify further. Given disproportionate damages by intense typhoons, this represents a heightened threat to people and properties in the region.
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