Climate Change & India’s Monsoons Katie Boyer May 6, 2008

Why India? 1.13 billion people – 2nd most populous country in the world – 1/6th the world’s population Over 200 million citizens of India are undernourished Agriculture employs 70% of people and produces 25% of the nation’s GDP 1/4th of exports are agricultural goods Country depends on rain! Most of the annual 975 mm of rain comes in form of annual tropical monsoon Water fills tributaries used for drinking water Rice = staple food of 65% of the population = 55% of India’s rice is rain fed

India’s Monsoons Stems from the differences in temperature & pressure between the land and the ocean 2 components in control: Land component = Eurasian (Himalayan) snow cover Ocean component = ENSO Results Northwestern India – little rainy period Southern & Northeastern India – more rain & longer season Highly susceptible to variation in rains and even failure

El Nino/ Southern Oscillation Positive Feedback Loop: Weakening winds  Decreased upwelling in SA  Lowering thermocline  Warmer ocean temperatures  Weakening winds

Himalayan Snow Cover Extent of rainfall negatively correlated with extent of Eurasian snowfall Less winter precipitation  less cooling of continental land mass & lower albedo  higher rainfall (non-ENSO) Relationship diminishes during El Nino years

ENSO Years & Monsoon Global warming seems to weaken relationship Causes warming oceans & displacement of Walker circulation  displaces rainfall producing systems 132 year record of India’s rain = every drought was accompanied by El Nino year (but not vice versa) Followed by La Nina, which causes floods

Forecasting Early methods used snow cover as only factor in predicting monsoon Important for disaster mitigation, crop planning, and power generation Global dimming Pollutants are blowing offshore, blocking sunlight, and shifting heating patterns that drive the monsoon Reduction of particulate matter may increase difference between land & sea temps

El Nino-like State A study of 79 coupled ocean-atmosphere simulations from 12 different climate models based on 6 different IPCC scenarios (Paeth et al.) All scenarios = substantial warming in eastern tropical Pacific amounting to 5°C until 2100 Results  failed monsoon, drought, dried out soils, decreased land fertility, famine

La Nina-like State 12 simulations (Doherty and Hulme) 4 = inconclusive 2 = El Nino-like state Results  shifting rains, intensification of the monsoon, flooding, reversal of the ENSO system

Personal Conclusion Higher ocean temperatures during more frequent ENSO years may create more fuel for future ENSO years  move into a permanent El Nino-like state Droughts in areas that are normally wet and floods in areas that are normally dry – 2007 produced massive flooding across India More models are necessary Ethics  Who’s to blame? Who needs to act?

Affects on India Floods, drought, tornadoes, plant diseases, insect pests Dried up major river basins Famine Northern India expected to experience the greatest warming trend Water shortage Dry areas get drier while wet areas get wetter Shift in biodiversity 10% increase in area prone to malaria by 2080 Sea level rise of 1 meter could displace 7 million people