NOAA Projects Fewer, But Stronger Storms From Climate Change

26 08 2008

The following is NOAA’s position on climate change and hurricanes:

Given the high degree of interest in the possible relationship between climate change and tropical cyclones (including hurricanes and typhoons), a new summary statement on the topic has been developed by the global community of tropical cyclone researchers and forecasters as represented at the 6th International Workshop on Tropical Cyclones of the World Meteorological Organization (November 2006). A more comprehensive statement was also developed at the workshop.

The summary statement notes the following: “The surfaces of most tropical oceans have warmed by 0.25-0.5 degree Celsius during the past several decades. The Intergovernmental Panel on Climate Change (IPCC) considers that the likely primary cause of the rise in global mean surface temperature in the past 50 years is the increase in greenhouse gas concentrations….

…Some recent scientific articles have reported a large increase in tropical cyclone energy, numbers, and wind-speeds in some regions during the last few decades in association with warmer sea surface temperatures. Other studies report that changes in observational techniques and instrumentation are responsible for these increases.”

Consensus statements by the workshop participants

“1. Though there is evidence both for and against the existence of a detectable anthropogenic signal in the tropical cyclone climate record to date, no firm conclusion can be made on this point.

2. No individual tropical cyclone can be directly attributed to climate change.

3. The recent increase in societal impact from tropical cyclones has been largely caused by rising concentrations of population and infrastructure in coastal regions.

4. Tropical cyclone wind-speed monitoring has changed dramatically over the last few decades leading to difficulties in determining accurate trends.

5. There is an observed multi-decadal variability of tropical cyclones in some regions whose causes, whether natural, anthropogenic or a combination, are currently being debated. This variability makes detecting any long-term trends in tropical cyclone activity difficult.

6. It is likely that some increase in tropical cyclone peak wind-speed and rainfall will occur if the climate continues to warm. Model studies and theory project a 3-5% increase in wind-speed per degree Celsius increase of tropical sea surface temperatures.

7. There is an inconsistency between the small changes in wind-speed projected by theory and modeling versus large changes reported by some observational studies.

8. Although recent climate model simulations project a decrease or no change in global tropical cyclone numbers in a warmer climate there is low confidence in this projection. In addition, it is unknown how tropical cyclone tracks or areas of impact will change in the future.

9. Large regional variations exist in methods used to monitor tropical cyclones. Also, most regions have no measurements by instrumented aircraft. These significant limitations will continue to make detection of trends difficult.

10. If the projected rise in sea level due to global warming occurs, then the vulnerability to tropical cyclone storm surge flooding would increase.”

The full texts of the summary statement and comprehensive statement should be consulted for more details and context.

Read more here.

 

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