WMO Consensus Statement on Tropical Cyclones and Climate Change
HYPERLINK "http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/001005wmo_consensus_statem.html" http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/001005wmo_consensus_statem.html
The World Meteorological Organization (WMO) has just released two updated statements on the state of science on tropical cyclones and climate change. The statements have been released today through the HYPERLINK "http://www.imn.ac.cr/" Instituto Meteorologico Nacional, San Jose, Costa Rica. Anyone referencing this post or the statements, please do acknowledge them as the source.
We are pleased that the WMO statements are 100% consistent with the views on this subject that we have been sharing over the past few years. In particular, it should now be completely unambiguous that those who are representing hurricane impacts as being related to greenhouse gas emissions, without acknowledging that this is not a widely shared perspective among scientists, are either cherry picking the relevant science or misrepresenting the community consensus. As a matter of policy, those interested in addressing the impacts of tropical cyclones on people and economies necessarily should be focued on adaptive responses. We have obviously made this case for a while, now there is no ambiguity.
Read on for details on the content of the statements.
The summary statement ( HYPERLINK "http://sciencepolicy.colorado.edu/prometheus/archives/IWTC_Summary.pdf" PDF) is one page and reflects a consensus among all particpants (125 people from 34 countries) at the just-concluded International Workshop on Tropical Cyclones in Costa Rica. The statement describes its authorship as follows:
The global community of tropical cyclone researchers and forecasters as represented at the 6th International Workshop on Tropical Cyclones of the World Meteorological Organization has released a statement on the links between anthropogenic (human-induced) climate change and tropical cyclones, including hurricanes and typhoons.
The ten consensus statements are as follows:
Consensus Statements by International Workshop on Tropical Cyclones-VI (IWTC-VI) 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 largely been 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.
In addition the WMO has released a lengthy statement ( HYPERLINK "http://sciencepolicy.colorado.edu/prometheus/archives/IWTC_Statement.pdf" PDF) co-authored by the WMO Tropical Meteorology Research Programme Committee, with members, John McBride (Australia, Committee Chair); Kerry Emanuel, Thomas Knutson, Chris Landsea, Greg Holland, Hugh Willoughby (USA); Johnny Chan, C-Y Lam (Hong Kong, China); Julian Heming (United Kingdom), Jeff Kepert (Australia).
The Committee's statement describes its purpose as follows:
This statement was developed, discussed and endorsed at the World Meteorological Organization (WMO) Sixth International Workshop on Tropical Cyclones, San Jose Costa Rica, November 2006. These invitation-only WMO International Tropical Cyclone Workshops are held every four years to bring together researchers and practitioners in the field of tropical cyclone forecasting. The Sixth Workshop was attended by 125 delegates from 34 different countries and regions. The Statement has been requested by WMO leadership and many heads of National Meteorological and Hydrological Services so they can respond to questions from the media, and also to assist in advising their governments on future activities and how to respond to climate change effects.
The statement includes the following conclusions:
On debate surrounding the trends documented in the Emanuel and Webster et al. papers from 2005: "This is still hotly debated area for which we can provide no definitive conclusion."
On what to expect for the future: "Given the consistency between high resolution global models, regional hurricane models and MPI theories, it is likely that some increase in tropical cyclone intensity will occur if the climate continues to warm."
On attribution of recent storms and seasons: "The possibility that greenhouse gas induced global warming may have already caused a substantial increase in some tropical cyclone indices has been raised (e.g. Mann and Emanuel, 2006), but no consensus has been reached on this issue."
On the societal factors driving losses: "Recent decades have seen a continuous increase in economic damage and disruption by tropical cyclones. This has been caused, to a large extent, by increasing coastal populations, by increasing insured values in coastal areas (e.g., Pielke 2005) and, perhaps, a rising sensitivity of modern societies to disruptions of infrastructure. For developing countries large loss of human life will continue as the increasing coastal populations are a result of population growth and social factors that are not easily countered (Zapata-Marti, 2006)."
On the expectations of new knowledge in this area: "Because of the rapid advances being made with this research, the findings in this statement may be soon superceded by new findings. It is recommended that a careful watch on the published literature be maintained."
Bottom line?
The perspective that we have provided here over the past several years and summarized in two BAMS articles has held up extremely well.
Posted on November 30, 2006 01:41 PM
http://sciencepolicy.colorado.edu/prometheus/archives/IWTC_Summary.pdf
http://sciencepolicy.colorado.edu/prometheus/archives/IWTC_Statement.pdf