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6 February 2013


Typhoon Committee considers impact of climate change

The influence of climate change on tropical cyclone activity in the western North Pacific basin remains uncertain and more research will be required to understand the relative contributions of natural variations and climate change linked to human activity, according to a new analysis of the world’s most active tropical cyclone region.

The United Nations Economic and Social Commission for Asia and the Pacific (UNESCAP)/World Meteorological Organization (WMO) Typhoon Committee considered the Second Assessment Report on the Influence of Climate Change on Tropical Cyclones in the Typhoon Committee Region at its recent meeting in Hong Kong, China.  The report summarized the results and findings from research conducted by Members on the long-term trends of tropical cyclone activity in the region.

The assessment report indicated that, with considerable inter-annual and inter-decadal variations in the tropical cyclone activity in the western North Pacific basin, it remains uncertain whether there has been any detectable human influence on tropical cyclone frequency, intensity, precipitation, track, or related aggregated storm activity metrics in this basin.     

The report also noted some regional shifts in tropical cyclone activity in the basin, such as a decreasing trend in tropical cyclone occurrence in part of the South China Sea and an increasing trend along the east coast of China during the past 40 years.   This change is apparently related to the changes in the large scale steering flow, though the cause of the circulation changes remains unknown.   For the late 21st century projections of tropical cyclone activity in this basin, a review of available studies suggested that more models project decreases than increases in tropical storm frequency. Most studies project an increase in the tropical cyclone intensity and precipitation rates.  The vulnerability of coastal regions to storm surge flooding is expected to increase with future sea-level rise and coastal development, although this vulnerability will also depend on future storm characteristics.

The Typhoon Committee’s report was based on published papers as well as the analysis of the tropical cyclone activities and the survey results of impacts on Members’ states in the region. It considered the time series of cyclone frequency and intensity, as well as possible changes of track pattern, genesis location and impacts of tropical cyclones.

The Typhoon Committee comprises 14 Members: Cambodia; China; Democratic People's Republic of Korea; Hong Kong, China; Japan; Lao People's Democratic Republic; Macao, China; Malaysia; the Philippines; Republic of Korea; Singapore; Thailand; Socialist Republic of Vietnam; and the USA. The committee provides a forum for international collaboration to build disaster resilience and mitigate the impacts of tropical cyclones in the Asia-Pacific region.

Busy 2012 season

The western North Pacific basin has the most intense tropical cyclone activity of any basin.

In 2012, the region saw a busy tropical cyclone season, with 25 events which reached Tropical Storm intensity or higher, according to WMO’s Regional Specialized Meteorological Centre Tokyo. There were also more cases of co-existing  typhoons (and as such, complicated interaction in terms of cyclone motion), typhoon strikes in quick succession, significant intensification ahead of landfall, and landfall impact over coastal areas at higher latitudes.  All these presented real challenges to reliable forecasting and warning of rain, wind and storm surge associated with changes in cyclone tracks, intensity and structure.

With a concentration of rapid economic and population growth in coastal areas, vulnerability to tropical cyclone related hazards such as extreme winds, torrential rain, flash flooding and storm surge substantially increased.  The Typhoon Committee will therefore step up efforts on projects on urban flood risk management, coastal multi-hazards early warning system,  and severe weather forecasting.

“Hato” replaces “Washi”

In the annual review of tropical cyclone names, the Typhoon Committee agreed to a new name “Hato” a Japanese term for “pigeon” to replace “Washi”, which was retired. Conventionally, the use of names of tropical cyclones that caused catastrophic damage is discontinued upon the request of Members.  Mindanao Island, an area in the Philippines rarely hit by tropical cyclones, was devastated by the passage of Severe Tropical Storm Washi in mid December 2011.  With hours of torrential rain causing extensive flooding and landslides, thousands of people were killed, roads and bridges were destroyed, and overall damage was estimated at nearly USD 50 million. Mindanao was also hit by Typhoon Bopha in December 2012. The Typhoon Committee will agree on an alternative name to replace Bopha at its next meeting.

Details on naming of tropical cyclones

Typhoon Committee official press release

Further details on the Second Assessment Report on the Influence of Climate Change on Tropical Cyclones in the Typhoon Committee Region at:









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