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Climate Change & Tropical Cyclones

Climate Change & Tropical Cyclones. Current Weather Tropical Cyclone Review Broader Context of Tropical Cyclones Previous Debates in Scientific Literature Group Activity For Next Class : Read IPCC AR5 Ch. 4 (pp. 344-360) Reminder: Exam III on 4 April!. Tropical Cyclones. Figure 8.26.

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Climate Change & Tropical Cyclones

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  1. Climate Change & Tropical Cyclones • Current Weather • Tropical Cyclone Review • Broader Context of Tropical Cyclones • Previous Debates in Scientific Literature • Group Activity • For Next Class: Read IPCC AR5 Ch. 4 (pp. 344-360) • Reminder: Exam III on 4 April!

  2. Tropical Cyclones Figure 8.26

  3. North Carolina coast experiences a higher frequency of tropical cyclone activity than anywhere else in the Atlantic basin. Changes in tropical cyclone activity will have a significant impact on North Carolina! Konrad & Perry (2009), Int. J. Clim.

  4. Tropical Cyclone Trends • Are tropical cyclones becoming more frequent? • Are they getting stronger? • Is destructiveness from land-falling tropical cyclones increasing? • Attribution?

  5. Broader Context • “Theory and modeling predict that tropical cyclone intensity should increase with increasing global mean temperatures” (Emanuel 2005) • Record hurricane season of 2004 and Katrina in 2005 contributed to scientific, public, and media interest in the possible connections between anthropogenic warming and tropical cyclone behavior. • 2015 Pacific hurricane season also set new records

  6. Who are Key Players? • Dr. Kerry Emanuel, Massachusetts Institute of Technology (MIT) • Dr. Roger Pielke, Jr., University of Colorado • Dr. Christopher Landsea, NOAA’s National Hurricane Center

  7. Emanuel (2005) • Power Dissipation Index (PDI), a measure of potential destructivenss of tropical cyclones, has increased markedly since the mid-1970s. • PDI is highly correlated with tropical sea-surface temperatures (SSTs). • “Results suggest that future warming may lead to an upward trend in tropical cyclone destructive potential and – taking into account an increasing coastal population – a substantial increase in hurricane-related losses in the twenty-first century.”

  8. PDI (Power Dissipation Index) has increased since 1970s for Atlantic and W. Pacific tropical cyclones. Emanuel (2005), Nature

  9. Pielke, Jr. (2005) Response • “My analysis of a long-term data set of hurricane losses in the United States shows no upward trend once the data are normalized to remove the effects of societal changes.” • “. . . it is misleading to characterize Emanuel’s results as indicating an increase in ‘destructiveness’ or as an indication of future increases in destruction resulting from changes in the PDI.”

  10. Landsea (2005) Response • “I question his [Emanuel’s] analysis on the following grounds: it does not properly represent the observations described; the use of his Atlantic bias-removal scheme may not be warranted; and further investigation of a substantially longer time series for tropical cyclones affecting the continental United States does not show a tendency for increasing destructiveness.” • “It is difficult to separate out any anthropogenic signal from the substantial natural multidecadal oscillations with a relatively short record of tropical-cyclone activity.” • “. . . claims to connect Atlantic hurricanes with global warming are premature.”

  11. No trend in the PDI of U.S. land-falling tropical cyclones. Landsea (2005), Nature

  12. Hurricane Sandy • Did Anthropogenic Global Warming cause Hurricane Sandy? • http://www.youtube.com/watch?v=YPfAvgJLDyA

  13. Group Activity (Knutson et al. 2010) • Do past changes in any tropical cyclone activity exceed variability expected through natural causes? • How is greenhouse warming likely to influence tropical cyclone activity? • Frequency, intensity, and rainfall? • Genesis, tracks, duration, and surge flooding?

  14. Knutson et al. (2010) • “We cannot at this time conclusively identify anthropogenic signals in past tropical cyclone data.” • “A substantial human influence on future tropical cyclone activity cannot be ruled out, however, and could arise from several mechanisms (including oceanic warming, sea-level rise, and circulation changes).”

  15. Capital Weather Gang • Northern Hemisphere’s Record-Shattering Tropical Cyclone Season: https://www.washingtonpost.com/news/capital-weather-gang/wp/2015/11/04/the-northern-hemispheres-record-shattering-tropical-cyclone-season-by-the-numbers/

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