Past holds the key to fu­ture

Sci­en­tists are ex­plor­ing ev­ery cor­ner of the planet for pre­his­toric clues to understand the fu­ture of mon­soon

Down to Earth - - PALAEO CLIMATOLOGY -

They say that history has a habit of re­peat­ing it­self. Cli­ma­tol­o­gists and sci­en­tists study­ing the history of South Asian mon­soon must hope that the adage holds true, be­cause if it does, their stud­ies could give in­sights into the fu­ture of mon­soon.

Faced with the un­pre­dictabil­ity of our mon­soons and baf­fled by the pe­ri­odic rev­e­la­tions of com­plex­i­ties that are pos­si­bly in­flu­enc­ing its evo­lu­tion, re­searchers have turned to palaeo­cli­ma­tol­ogy for clues to how the mon­soon might re­act to cli­mate change. Palaeo­cli­ma­tol­ogy uses in­di­ca­tors stored in ge­o­log­i­cal ar­chives, or prox­ies, to re­con­struct cli­matic pat­terns from pre­his­toric times. Th­ese are de­coded us­ing dat­ing pro­cesses that can de­ci­pher data recorded sev­eral mil­lion years ago.

“Some of th­ese prox­ies in­clude chem­i­cal, iso­topic and bio­genic com­po­si­tion of sed­i­ments which pro­vide in­for­ma­tion on past tem­per­a­tures, sea level vari­a­tion and mon­soon vari­abil­ity,” says Ravi Bhushan, re­searcher at the Phys­i­cal Re­search Lab­o­ra­tory (prl) in Ahmed­abad,Gu­jarat.

Work­ing on the as­sump­tion that ba­sic pro­cesses dic­tat­ing cli­matic pat­terns have re­mained con­stant through the ages, his­toric data holds un­de­ni­able value in un­der­stand­ing the cur­rent tra­jec­to­ries of mon­soon.The data can be used to recre­ate long-term cli­mate pat­terns, and by see­ing where the cur­rent mon­soon is lo­cated on the ge­o­log­i­cal scale, we can spec­u­late what tra­jec­tory it is go­ing to take.

IN­FOR­MA­TION RE­SERVES

This data is found in nat­u­rally formed ar­chives such as ice cores, tree rings, sed­i­ments from wa­ter bod­ies and cave de­posits. Re­searchers have been ex­plor­ing th­ese ge­o­log­i­cal sources for in­for­ma­tion on pre­his­toric mon­soon:

Th­ese can pro­vide in­for­ma­tion about cli­mate in the most re­cent past. A team study­ing palaeo­cli­matic trends in mon­soon at the In­dian In­sti­tute of Tech­nol­ogy-Mum­bai (iit-m) has used cross-sec­tions of tree trunks to re­con­struct weather pat­terns up to 2,000 years ago. H P Bor­gaonkar, lead sci­en­tist of the team, says, “The char­ac­ter­is­tics of each ring re­flects cli­matic con­di­tions of the pre­vi­ous year. For ex­am­ple, nar­row rings in­di­cate ex­treme weather such as droughts. The decadal epochs of mon­soons—the 31 year cy­cles of alternate ex­ces­sive and de­fi­cient phases that we are ob­serv­ing

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