Climate change and extreme precipitation: Is there a connection?

Although an individual extreme precipitation event cannot be solely attributed to climate change, as pointed out in scientific studies, climate change will likely affect the frequency of occurrence of such events in the long term. It is because the tropospheric warming due to increased anthropogenic (human induced) greenhouse gases can lead to an increase in the water-holding capacity of the atmosphere. The warming may also enhance the hydrological cycle and atmospheric instability. A less stable atmosphere with more water vapour in the air will provide a more favourable condition for intense precipitation events.

Moreover, some studies suggest that urbanization effect may also partly contribute to heavier rain in urban areas. This may be attributed to the urban heat island effect that enhances the convective activities, the increased roughness over a city that slows down the storm movement and the increase in the concentration of suspended particulates from urban activities that helps the formation and development of rain-bearing clouds.

Locally in Hong Kong, a study on the past occurrences of extreme rainfall indicates that heavy rain events in Hong Kong have become more frequent in the last 120 years or so.

Reference:

Weather extremes in a changing climate: Hindsight on Foresight, World Meteorological Organization, WMO-No. 1075, 2011

Min, S.K., X. Zhang, F.W. Zwiers and G.C. Hegerl, Human contribution to more-intense precipitation extremes, Nature 470, 378-381, 2011

Allan, R. P. and B. J. Soden, Atmospheric warming and the amplification of precipitation extremes, Science 321, 1481-1484, 2008

IPCC AR 4, WG1, Chapter 3, Section 3.4.2.1 : Surface and Lower-Tropospheric Water Vapour, page 272-273, 2007

Shepherd, J. M., H. Pierce, A. J. Negri, Rainfall modification by major urban areas: observations from spaceborne rain radar on the TRMM satellite, J. Appl. Meteor. 41, 689-701, 2002

Cao, K., Z. Ge, M. Xue and Y. Song, Analysis of Urban Rain Island Effect in Shanghai and Its Changing Trend, Water Resources and Power 27 (5), page 31-33, 54, 2009

Wong, M.C., H.Y. Mok and T.C. Lee, Observed Changes in Extreme Weather Indices in Hong Kong, Int. J. Climatol., October 2010, DOI: 10.1002/joc.2238, HKO Reprint No. 941

Note : Precipitation is the general term for rainfall, snowfall and other forms of frozen or liquid water falling from clouds.