Madhav Khandekar: The Climate Monsoon
Monsoon droughts and floods have occurred at irregular time intervals with no linkage to recent global warming
The Indian monsoon is the most important regional climate system, impacting about two billion people in South Asia on an annual basis. A good monsoon season with well distributed rains through the summer (June-September) months provides a great stimulant to the agriculturally dominated economies of India and other South Asian nations.
As an example, a good monsoon year can generate upwards of US$350 billion in economic activity, just for India. A drought on the other hand can inflict severe socioeconomic stress due to depleted crop yields and reduced water supply. The present climate change debate in the Canadian media has disappointingly ignored this important tropical climate system while extensively discussing mid latitude extreme weather events and their linkage to present climate change.
A knowledge of monsoon inter-annual variability is essential for understanding climate change impacts. An excellent 200- year data set reveals that Indian monsoon droughts and floods have occurred at irregular time intervals with no linkage to recent climate change. Droughts and floods in Indian monsoon are found to be linked to large-scale ocean atmospheric features like the ENSO (El Niño Southern Oscillation) phase in the equatorial Pacific Eurasian winter snow cover and the Indian Ocean Dipole, a naturally occurring feature in the equatorial Indian Ocean. In addition, a host of other factors like topography and development of low-pressure systems in the Arabian Sea and the Bay of Bengal impact monsoon rains in a given season.
That is what makes monsoon prediction a truly challenging problem. Some of the worst droughts have occurred from the 1820s through the 1850s. Among some of the notable flood years were 1892, 1894, 1917, 1933 and 1961. The 1961 monsoon was the heaviest in 200 years. This led to extensive India-wide flooding , extensive damage to infrastructure and drowning of several hundred people. The 1972 monsoon was a major drought, which led to a sharp drop in the rice crop in particular. India had to import a lot of grain to replenish its depleted grain stock.
Most climate models have achieved only a limited success in predicting intra-seasonal or inter-annual variability of monsoon. As such, these models are of limited utility in providing early warning of an impending drought or flood. Statistical-empirical algorithms using indices of large-scale ocean atmospheric features appear to provide operationally useful guidelines with a lead time of a few weeks. This was the rationale for the pioneering correlation analysis initiated by Sir Gilbert Walker in India in the early 1900.
The India meteorological department has been using a similar algorithm based on four to five antecedent parameters and the seasonal forecast for the monsoon is issued by about mid April every year. These seasonal forecasts do seem to provide guidance for socioeconomic planning in India today. In summary, droughts and floods in the Indian monsoon have always occurred at irregular time intervals in the past and will continue to do so in future. Further, droughts and floods elsewhere and other extreme events like heat waves will continue to occur irregularly in the future with no linkage to human CO2 emissions.
It is tempting to refer to the present humanitarian crisis as thousands of migrants fleeing war torn regions travel to Europe. Against this grim backdrop, the present climate change is benign and poses no threat to world humanity. There is no climate catastrophe either at present or 50 years from now.
Madhav Khandekar, a former research scientist at Environment Canada, was an expert reviewer of the UN IPCC’s 2007 climate change documents. He gave a GWPF talk Tuesday on Indian monsoon variability and climate change at the U.K. House of Commons.