Precipitation In Climate Change

Climate change has been a major area of research and debate. It is defined as any statistically significant trend found in a climate variable [1]. These variables include rising sea levels, ice cover, and average temperature of the Earth. This review considers the changes in the levels and distribution of precipitation in predominantly USA. Precipitation is influenced by many factors including changes in the level of greenhouse gases in the atmosphere, temperature and aerosols [2].

Firstly, models show that future precipitation levels will not increase everywhere but depend on what region is looked at and the time of the year. The IPCC's Fourth Assessment Report [3] states that 'precipitation generally increases in the areas of regional tropical precipitation maxima (such as the monsoon regimes) and over the tropical Pacific in particular, with general decreases in the subtropics, and increases at high latitudes'. Overall, the average global precipitation rate per year is predicted to increase through to 2100. This is due to the approximately 5% increase in water vapour in the atmosphere [4]. The weather systems that control precipitation rely on this water vapour. This has resulted in an increase in the chance of heavy rain and snow. Parts of the world that will undergo particular increases in the intensity of precipitation are the tropical regions of the world and areas of high-altitude [3].

Furthermore, the quantity of precipitation arising during tropical storms is expected to increase, although the incidence of tropical storms globally will continue the same rate [5]. Wind speeds during storms are also likely to increase.

The US is a prime example where these divergent effects are demonstrated. In the period of winter to spring, northern areas expect a significant increase in precipitation levels while less is expected in southern areas [6]. This precipitation is more and more likely to take the form of rain as opposed to snow. By 2100, heavy downpours are predicted to occur up to every four years in certain regions. This is compared to the present rate of every twenty years [6].

The increase in frequency of heavy precipitation events is commonly attributed to the man-made release of greenhouse gases [7]. These permit energy from sunlight to get to the Earth's surface, but the infrared energy emitted is absorbed, resulting in warmer temperatures. This has profound consequences in climate change as increased heating increases evaporation. In these conditions, the atmosphere`s water holding capacity increases leading to more precipitation, particularly in North America during winter. In contrast, warming can also lead to more severe droughts as land surfaces dry faster.

Additionally, the effects of aerosols are to decrease the intensity and incidence of precipitation events [8]. The pollution conceals direct sunlight from the ground resulting in a drop in evaporation. This depletes the overall atmosphere moisture supply and hence takes longer for the appropriate amount of water vapour to build up.

Past records show the vastly fluctuating nature of precipitation from region to region. Nevertheless new models are becoming more effecting in predicting the outcomes of climate change in terms of extreme precipitation events [9].

References 1. http://www.fao.org/climatechange/65923/en/, FAO Climate Change and Bioenergy Glossary, last updated 18 April 2011. 2. Muller C. J., O'Gorman P. A., 2011, Nature Climate Change, 1, 266. 3. Meehl, G.A., T.F. Stocker, W.D. Collins, P. Friedlingstein, A.T. Gaye, J.M. Gregory, A. Kitoh, R. Knutti, J.M. Murphy, A. Noda, S.C.B. Raper, I.G. Watterson, A.J. Weaver and Z.-C. Zhao, 2007: Global Climate Projections. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 4. http://co2now.org/Know-the-Changing-Climate/Climate-Changes/ipcc-faq-changes-in-precipitation.html, How is Precipitation changing?, Adapted from Dai et al. (2004b). 5. IPCC, 2012: Summary for Policymakers. In: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation [Field, C.B., V. Barros, T.F. Stocker, D. Qin, D.J. Dokken, K.L. Ebi, M.D. Mastrandrea, K.J. Mach, G.-K. Plattner, S.K. Allen, M. Tignor, and P.M. Midgley (eds.)]. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK, and New York, NY, USA, pp. 1-19. 6. http://downloads.globalchange.gov/usimpacts/pdfs/20page-highlights-brochure.pdf, Global Climate Change Impacts in the Unites States, US Global Change Research Program, last updated June 2009. 7. Min S. K., Zhang X., Zwiers F. W., Hegerl G. C., 2011, Nature, 470, 378. 8. Rosenfeld D. et al., 2008, Science 321, 1309. 9. http://www.guardian.co.uk/environment/2011/dec/15/climate-change-rainfall, How will climate change affect rainfall?, D. Clark, last updated 15 December 2011.