IMPACTS OF CLIMATE CHANGE ON TROPICAL CYCLONES IN THE WESTERN NORTH PACIFIC BASIN. PART I: PAST OBSERVATIONS

This paper reviews the current state of the science on the relationship between climate change and historical tropical cyclone (TC) activity in the western North Pacific (WNP) basin, which is the region of the ESCAP/WMO Typhoon Committee members. Existing studies of observed changes of TC activity in this basin, such as frequency, intensity, precipitation, genesis location and track pattern are summarized. Results from a survey on impacts of past TC activity on various members of Typhoon Committee are reported, along with a review of studies of past WNP landfalling TCs. With considerable interannual and interdecadal variations in the TC activity in this 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. Also, the issues of homogeneity and consistency of best track data sets in the WNP further add uncertainty to relevant research studies. Observations indicate some regional shifts in TC activity in the basin, such as a decreasing trend in TC 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 local circulation changes in the eastern Asia and WNP, though the cause of the circulation changes remains unknown.