Weather & Climate | VOL. 16, ISSUE 96, May-June 2016

Stalagmites Reveal Past Drought Records

The Indian economy is primarily dependent on harvests, which in turn are regulated by monsoon rains. Frequent droughts and floods can not only have severe repercussions on public health, but significantly impair a country’s economy. Even when the monsoon is regular, one notices significant variations in the intensity, occurrence and duration on annual time scales. On longer timescales (centennial or millennial) the rains are found to be modulated by the interplay between the intensity of the insolation in the northern hemisphere, northward movement of the inter-tropical convergence zone (Gadgil, 2003) and changes in ice extent during glacial-interglacial periods (Zhinseng et al., 2011). These governing factors operate on different timescales and control decadal, centennial and millennial variability of monsoon rains.   Past Monsoons The fall of the Indus valley civilization could be partly attributed to the significant receding of monsoon over time (Staubwasser, 2003). Given the importance of rain and water for human survival, we need to understand and mitigate the causative processes behind droughts. Some concerns regarding monsoon are: Can natural changes in rainfall patterns be anticipated? Are their magnitudes predictable? Can the response of the Indian monsoon to anthropogenic disturbances be quantified? Can this information be used in future planning of water resources and food security under a changing climatic regime? The above questions require dealing with a complex earth system that needs continuous...

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