Gadget by The Blog Doctor.

Wednesday, February 2, 2011

Tropical cyclones in a warming world

What will be the effect on Tropical Cyclones (Hurricanes) as the world warms?

It is likely that extreme weather events will occur more frequently , but the effect on Tropical Cyclones is a complex one and open to misunderstanding.

The first half of the video below outlines the scientific evidence which can be summarised as follows:

1. There will be fewer tropical cyclones because of global warming ...
2. ... but those storms that do make landfall will be more powerful. So there will be more strong storms.
3. We are currently in a phase of heightened hurrican activity becasuse of a natural 60 to 80 year cycle that began in 1995 (in the Atlantic).
4. There is evidence to suggest that recent hurricanes may have become stronger because of global warming, but this isn't conclusive.

The Australian Bureau of Meteorology has posted an article on tropical cyclones at this link which agrees with the information presented in the video, as the following quotation shows:

There have been three recent studies producing projections for tropical cyclone changes in the Australian region. Two suggest that there will be no significant change in tropical cyclone numbers off the east coast of Australia to the middle of the 21st century. The third study, based on the CSIRO simulations, shows a significant decrease in tropical cyclone numbers for the Australian region especially off the coastline of Western Australia. The simulations also show more long-lived eastern Australian tropical cyclones although one study showed a decrease in long-lived cyclones off the Western Australian coast.

Each of the above studies finds a marked increase in the severe Category 3 - 5 storms. Some also reported a poleward extension of tropical cyclone tracks.

The second half of the video discusses the issue of sea level rise and low lying islands. Again the evidence is interesting and complex. Even if low lying islands will not be drowned, storm surges, coral bleaching and ocean acidification are a definite threat.


Below are the sources that the creator of the video used:
1) NBC news report: "Hurricanes and Global Warming Connection" on YouTube

2) "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment"
Webster et al, Science 2005

3) Half-degree increase in temp leads to approx 40% increase in hurricanes:
"Large contribution of sea surface warming to recent increase in Atlantic hurricane activity"
-- Saunders and Lea, Nature 2008

4) 60- to 80- year hurricane cycle responsible for hurricane activity:
"The Recent Increase in Atlantic Hurricane Activity: Causes and Implications."
Goldenberg et al, Science 2001

5) Photo of Hurrican Igor showing temperature difference:

6) Increased wind shear decreases hurricane activity:
"The Recent Increase in Atlantic Hurricane Activity: Causes and Implications." -- Goldenberg et al, Science 2001
and "Increased tropical Atlantic wind shear
in model projections of global warming" -- G. Vecchi, B. Soden, Geophysical Research Letters, 2007

7) paper postulating fewer tropical storms:

"Tropical Cyclones and Global Climate Change: A Post-IPCC Assessment"
-- Henderson-Sellers et al, Bulletin of the American Meteorological Society 1998

8) Papers confirming fewer storms:

"Increased tropical Atlantic wind shear
in model projections of global warming" -- G. Vecchi, B. Soden, Geophysical Research Letters, 2007

"Simulated reduction in Atlantic
hurricane frequency under 21st century
warming conditions."
-- Tom Knutson, Nature Geoscience 2008

"Warmer Ocean Could Reduce Number
Of Atlantic Hurricane Landfalls"
-- Wang et al, Geophysical Research Letters 2008

9) Expert panel paper:
"Tropical Cyclones and Climate Change"
-- Knutson et al, Nature Geoscience 2010

10) 10% increase in wind speed translates to a roughly 60% increase in damage:
"Climate and tropical cyclone activity: A new model"

11) Increase in number and proportion of category 4 and 5 hurricanes:
"Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment"
-- Webster, Science 2005

12) Nature paper that reached the same conclusion:
"Increasing destructiveness of tropical cyclones over the past 30 years"
-- K. Emanuel, Nature 2005

13) Global warming a factor in increased sea surface temperatures:
"Global Warming Surpassed Natural Cycles In Fueling 2005 Hurricane"
-- Trenberth and Shea, Geophysical Research Letters 2006

14) Boston Globe story "Katrina's Real Name" (Boston Globe August 30, 2005) at:

15) Fox news report on hurricane inactivity:
"Global Warming No Hurricanes" on YouTube

16) Global Warming = More Hurricanes at:

17) Discovery channel report on rising sea levels "Global warming -- what you need to know" found at:
"Kiribati - Global warming" on YouTube.

18) BBC report on Tuvalu found at "Tuvalu Island in the South Pacific" on YouTube.

19) Studies on accretion of coral atolls:
"Tropical cyclone creates a new land
formation on Funafuti atoll" -- J.E. Maragos et al, Science 1973.

"The nature and origin of coral reef
islands." -- Stoddart and Steers, Biology and Geology of
Coral Reefs 1977.

"Reef-island accretion and soil
development on Makin, Kiribati...."
-- Woodroffe and Morrison, CATENA, 2001

"The morphological response of atoll
islands to sea-level rise" -- Cowell and Kench. Journal of Coastal
Research 2001
Below are the rest of my sources for the last video (they wouldn't all fit on the original video description)

"New model of reef-island evolution...."
-- Kench et al, Geology 2005

20) Study showing 23 of 27 Pacific atolls stable or increasing in size:
"The dynamic response of reef islands to sea-level rise: Evidence from multi-decadal
analysis of island change in the Central Pacific"
-- Webb and Kench, Global and Planetary Change 2010-11-23

21) "Coral Reefs - Feeling the Heat with Jeff Corwin" on YouTube, produced by Defenders of Wildlife.

22) Explanation of bleaching:

"Bleaching Patterns of Four Species of Carribean Reef Corals" -- Fitt and Warner, Biology Bulletin 1995

"Coral bleaching: causes and consequences"
-- B. E. Brown, Coral Reefs, 1997

23) Most coral unable to change algae:
"Most corals may not change their symbionts."
-- TL Goulet, Marine Ecology Progress 2006

24) Refutation of Goulet:
"Multiple symbiotic partnerships are common in scleractinian corals, but not in octocorals:
Comment on Goulet"
-- Baker and Romanski, Marine Ecology Progress 2007

25) Coral thrived in northern latitudes during warm past:
"Correlations between sea surface temperature, circulation patterns and the distribution of hermatypic
corals of Japan"
-- Jen Veron, Continental Shelf Research, 1992

26) Coral may have difficulty migrating due to human activity:
"Coral reefs and Global Climate Change"
-- The Pew Center 2004

27) Potential acidification of oceans:
"Anthropogenic Decline in High-Latitude Ocean Carbonate by 2100"
-- JC Orr et al, nature 2005

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