Third assessment on impacts of climate change on tropical cyclones in the Typhoon Committee Region——Part Ⅰ:Observed changes, detection and attribution

Published findings on climate change impacts on tropical cyclones(TCs) in the ESCAP/WMO Typhoon Committee Region are assessed. We focus on observed TC changes in the western North Pacific(WNP) basin, including frequency, intensity, precipitation, track pattern, and storm surge. Results from an updated survey of impacts of past TC activity on various Members of the Typhoon Committee are also reported. Existing TC datasets continue to show substantial interdecadal variations in basin-wide TC frequency and intensity in the WNP. There has been encouraging progress in improving the consensus between different datasets concerning intensity trends. A statistically significant northwestward shift in WNP TC tracks since the 1980s has been documented. There is low-to-medium confidence in a detectable poleward shift since the 1940s in the average latitude where TCs reach their peak intensity in the WNP. A worsening of storm inundation levels is believed to be occurring due to sea level rise-due in part to anthropogenic influence-assuming all other factors equal. However, we are not aware that any TC climate change signal has been convincingly detected in WNP sea level extremes data. We also consider detection and attribution of observed changes based on an alternative Type II error avoidance perspective.