THE GUARDIAN: LINK: https://www.theguardian.com/environment/2020/nov/15/scientists-link-record-breaking-hurricane-season-to-climate-crisis CLIMATE CHANGE CAUSES RECORD BREAKING HURRICANE SEASON IN 2020.

CLAIM: Evidence is not so much in the number of tropical storms the Atlantic has seen, but in their strength. Hurricane Mitch in 1998 was the most destructive storm to hit Central America. But hundreds of thousands of subsistence farmers across the region have lost everything in flooding caused by Eta, which made landfall in Nicaragua as a category 4 hurricane on 3 November. Now, with a second hurricane projected to make landfall on Monday near where Eta did, even more could find themselves in the same situation. Climate scientists say that this year’s record-breaking hurricane season and the “unprecedented” double blow for Central America has a clear link to the climate crisis. In a 36-hour period Hurricane Eta went from a depression to a very strong category 4. This is just not normal. Probably it was the fastest spin up from a depression to a major hurricane in history. The evidence of the influence of the climate crisis is not so much in the record-breaking 30 tropical storms in the Atlantic so far this year, but the strength, rapid intensification and total rainfall of these weather systems. The warmer ocean waters that climate change brings are expected to make storms stronger and make them rapidly intensify more frequently and at a greater rate. These things have already been observed, particularly in the Atlantic, and it’s going to be increasingly so in coming decades. Central America has been one of the regions most affected by the climate crisis to date, first with Hurricane Mitch, and in recent years with more extreme weather patterns, particularly in what’s known as the dry corridor, which extends from northern Costa Rica all the way to southern Mexico. Heat is energy, depending on the prevailing weather conditions will intensify those conditions. People are dying! This is how the climate crisis has sparked an exodus from Central America to the US. In the dry corridor, that has meant more frequent, prolonged and intense droughts as well as heavier rainfall when it does come, often causing flash flooding that washes away crops. Subsistence farmers in the region have struggled to adapt to the new reality, and many in the region have simply given up and left. The climate crisis – and the hunger it brings – is increasingly being recognized as a major driver of emigration from the region. There aren’t a lot of options for Central America to deal with the global warming issue. There are going to be a lot migrants and in fact, a lot of the migration that’s already happening in recent years is due to the drought that started affecting Central America back in 2015. Hondurans migrated to the US in significant numbers for the first time following Hurricane Mitch. In the year before the Covid-19 pandemic, more than 250,000 Hondurans were apprehended at the US south-west border, more than double any previous year and surpassed only by its neighbor to the north, Guatemala. According to the Red Cross, at least 2.5 million people were affected by Hurricane Eta, including 1.7 million in Honduras. Many who have lost everything are already considering or making plans to migrate to the US and groups are beginning to organize caravans via social media. Unable to fulfill the needs of their citizens before the pandemic. The economic downturn has stretched the finances of Central American governments to the brink. And unlike following previous natural disasters, the international community is dealing with pandemic-related problems of its own and is unlikely to step in to fill the gap. Hurricane Iota could lead to even more widespread devastation across the region. Many areas still have high water levels from Eta, levees have been damaged or destroyed, dams are at or near capacity, and the saturated land could lead to more landslides like in Guatemala, where dozens are feared dead after part of a mountainside community was buried in mud. The Atlantic hurricane season is expected to last until December this year, meaning that Iota might not be the last. When a season like 2020 keeps on cranking these things out, it’s going to keep on doing that.

RESPONSE: Climate science has used a large number of climate model simulations to project the possible impacts of global warming on tropical cyclones. What they have concluded from these studies is that (1) global warming will cause higher sea surface temperature (SST) and the higher SST in turn will increase the amount of energy in tropical cyclones. Therefore global warming will cause the ACE cyclone intensity measure, accumulated cyclone energy, to rise over time as the globe warms.

The details of these expected impacts are described in the research paper Tropical cyclones and climate change, Nature Geoscience 3.3 (2010): 157-163. In the paper, Tom Knutson spells out exactly what climate science claims in terms of the impact of AGW climate change on tropical cyclones with climate model predictions of the effect of rising SST on tropical cyclones.

His main points are as follows: (1) Globally averaged intensity of tropical cyclones will rise as AGW increases SST. Models predict globally averaged intensity increase of 2% to 11% by 2100. (2). Models predict falling globally averaged frequency of tropical cyclones with frequency decreasing 6%-34% by 2100. (3). The globally averaged frequency of “most intense tropical cyclones” should increase as a result of AGW. The intensity of tropical cyclones is measured as the ACE (Accumulated Cyclone Energy). (4). Models predict increase in precipitation within a 100 km radius of the storm center. A precipitation rise of 20% is projected for the year 2100. (5) Extremely high natural variability in tropical cyclone data at an annual time scale requires longer, perhaps a decadal time scale in the study of these trends. (6) Model projections for individual cyclone basins show large large natural variability from year to year. (7) Model projections also show large natural variability among the cyclone basins in any cyclone season. (8) Thus, no testable implication can be derived for studies of individual basins or of a single cyclone season.

IN THIS CONTEXT OF THE CLIMATE SCIENCE OF TROPICAL CYCLONES, WE DO EXPECT AN IMPACT OF GLOBAL WARMING ON TROPICAL CYCLONES, BUT THE DATA SERVE AS EMPIRICAL EVIDENCE OF SUCH IMPACTS ONLY WHEN ALL SIX CYCLONE BASINS ARE STUDIED OVER MANY DECADES.

NO INFORMATION ABOUT THE IMPACT OF GLOBAL WARMING ON TROPICAL CYCLONES CAN BE FOUND IN THE DATA FOR A SINGLE CYCLONE BASIN NOR IN THE DATA FOR A SINGLE CYCLONE SEASON, MUCH LESS THE DATA FOR A SINGLE CYCLONE SEASON IN A SINGLE CYCLONE BASIN. THE STUDY OF THE 2020 HURRICANE SEASON IN THE NORTH ATLANTIC CYCLONE BASIN IS THUS FOUND TO BE FLAWED.

THE FINDINGS PRESENTED IN THE CLIMATE CHANGE ALARM ABOVE ARE REJECTED ON THIS BASIS.

RELATED POSTS ON TROPICAL CYCLONES

LINK#1: https://tambonthongchai.com/2018/11/28/trends-in-tropical-cyclone-activity/ 

LINK#2: https://tambonthongchai.com/2019/03/22/ace-sst/ 

LINK#3: https://tambonthongchai.com/2019/04/04/1737/ LINK#4: https://tambonthongchai.com/2019/08/01/tropical-cyclones-climate-change/ 

LINK#5: https://tambonthongchai.com/2020/03/04/agwcyclones/