Warming world blamed for strong hurricanes
Seems as though if we wanna play the blame game re Nola, we could look at who has refused to accept the reality of global warming. Methinks plenty of scientists have an opinion when the gubment says "We had no idea something like this could happen." How could you, when even the commander in chief has to ask for a bathroom break. What are we, in fifth grade Dubya?
Warming world blamed for more strong hurricanes
NewScientist.com news service
A massive global increase in the number of strong hurricanes over the past 35 years is being blamed on global warming, by the most detailed study yet. The US scientists warn that Katrina-strength hurricanes could become the norm.
Worldwide since the 1970s, there has been a near-doubling in the number of Category 4 and 5 storms – the strength that saw Hurricane Katrina do such damage to the US Gulf coastline late in August 2005.
Peter Webster of the Georgia Institute of Technology, Atlanta, says the trend is global, has lasted over several decades and is connected to a steady worldwide increase in tropical sea temperatures. Because of all these factors, it is unlikely to be due to any known natural fluctuations in climate such as El Niño, the North Atlantic Oscillation or the Pacific Decadal Oscillation.
“We can say with confidence that the trends in sea surface temperatures and hurricane intensity are connected to climate change,” says Webster’s co-author Judy Curry, also of the Georgia Institute of Technology. The team looked at the incidence of intense tropical storms and the study results are the strongest affirmation yet that Katrina-level hurricanes are becoming more frequent in a warmer world.
The study finds there has been no general increase in the total number of hurricanes, which are called cyclones when they appear outside the Atlantic. Nor is there any evidence of the formation of the oft-predicted “super-hurricanes”. The worst hurricane in any year is usually no stronger than in previous years during the study period.
But the proportion of hurricanes reaching categories 4 or 5 – with wind speeds above 56 metres per second – has risen from 20% in the 1970s to 35% in the past decade.
“This trend has lasted for more than 30 years now. So the chances of it being natural are fairly remote,” says Greg Holland of the National Center for Atmospheric Research (NCAR) at Boulder, Colorado
Moreover, says Webster, natural fluctuations tend to be localised. “When the east Pacific warms, the west Pacific cools, for instance. But sea surface temperatures are rising throughout the tropics today.” The surface waters in the tropical oceans are now around 0.5°C warmer during hurricane seasons than 35 years ago.
Hurricanes form when ocean temperatures rise above 26°C. “The fuel for hurricanes is water vapour evaporating from the ocean surface. It condenses in the air and releases heat, which drives the hurricane’s intensity,” says Webster.
“The tendency to Katrina-like hurricanes is increasing,” Holland says. Without the warmer sea-surface temperatures, “Katrina might only have been a category 2 or 3”.
Take for example this picture of the sst's of the Gulf of Mexico on Aug. 27:
Is it not obvious that the intense heating of our oceans is fueling these deadly cyclones?
All the data for sea surface temperatures and hurricane numbers and intensities come from satellite data. “We deliberately limited this study to the satellite era because of the known biases [in the data] before this period,” says Webster.
This is the third report in recent months highlighting the growing risk to life and property round the world from hurricanes and tornadoes. In June, NCAR’s Kevin Trenberth reported a rising intensity of hurricanes in the North Atlantic.
And in August, Kerry Emanuel of MIT found a 50% increase in the destructive power of tropical storms in the past half century.
Journal reference: Science (vol 309, p 1844)