Indian Monsoon Variability Global Warming Madhav Khandekar CANADA

Indian Monsoon Variability & Global Warming Madhav Khandekar CANADA Expert Reviewer IPCC 2007 Climate Change Heartland Conference on Climate Change Chicago May 21 -23 2012

Abstract n An analysis of Indian Summer Monsoon Rainfall (ISMR) reveals that droughts and floods have occurred irregularly throughout a 200 -year long excellent dataset with NO Link to “global warming OR climate change” at this point in time. Heartland Conference on Climate Change Chicago May 21 -23 2012

Monsoon: General Notes n n n Indian/Asian monsoon is the largest seasonal abnormality in the global climate system Indian/Asian monsoon affects about 4 billion people of south Asia. Timely arrival and well distributed rainfall during the summer season (May-October) is critical for agriculturally dominated countries of south Asia. Climate models have achieved only a limited success so far in simulating many features of global and regional monsoon. Most climate models project monsoon circulation to intensify in a warmer future climate. In reality, Monsoon circulation has weakened in the last fifty years. Heartland Conference on Climate Change Chicago May 21 -23 2012

Basic Facts on Indian Summer Monsoon 1. Summer (June-September) rains most important for whole of India for agriculture & water supply 2. Mean rainfall ~90 cm; On west coast ( Mumbai-Goa-Kerala Coast)~ 150 -200 cm; central India ~100 -125 cm; northwest India ~50 cm 3. Monsoon onset on west coast tip of India ~June 7 th 4. Despite year-to-year variability, this onset date is robust: Over Bay of Bengal & northeast, monsoon arrival ~1 -12 June 5. By 25 June, monsoon spreads over most of India Heartland Conference on Climate Change Chicago May 21 -23 2012

Heartland Conference on Climate Change Chicago May 21 -23 2012

Highest/Lowest Rainfall n n Highest One Year Rainfall: Cherrapunji 2646 cm Aug 1860 - July 1861 Highest One Month Rainfall: Cherrapunji 930 cm July 1861 Highest 2 -day Rainfall: 41 in ( ~105 cm) Mumbai July 2005 Lowest seasonal Rainfall: 33 mm (1918), 49 mm (1899) in West Rajasthan: Both the years ( 1899 &1918 ) were severe drought years over whole of India Heartland Conference on Climate Change Chicago May 21 -23 2012

Major Flood Years 1892, 1917, 1933, 1961, 1970, 1975 Major drought years 1868, 1877, 1899, 1918, 1951, 1972, 1987 Heartland Conference on Climate Change Chicago May 21 -23 2012

Large-scale controls of Indian Monsoon n ENSO phase in the equatorial Pacific (El Nino linked to drought) n Eurasian snow cover, previous winter (Heavy snow cover weakens monsoon) n Equatorial stratospheric wind oscillation (QBO: quasi-biennial oscillation) n Indian Ocean Dipole (IOD) These large-scale controls and their various phases, produce major droughts/floods in summer monsoon Heartland Conference on Climate Change Chicago May 21 -23 2012

Regional controls of Monsoon Ax is of Mo nso on tro ug h Low Depressions traveling along Monsoon trough rn ste wes tcoa ats Gh then reng s st sure We Pres in st ra Heartland Conference on Climate Change Chicago May 21 -23 2012

ENSO (El Nino-Southern Oscillation) phases in the equatorial Pacific Heartland Conference on Climate Change Chicago May 21 -23 2012

The 1997/98 El Nino structure at about Sep 1997 Heartland Conference on Climate Change Chicago May 21 -23 2012

Equatorial stratospheric wind oscillation (QBO) at ~20 -22 km level with about 26 -month (east-west) period. Heartland Conference on Climate Change Chicago May 21 -23 2012

A schematic of Indian Ocean Dipole (IOD) Positive phase: warmer SSTs in west equatorial ocean Heartland Conference on Climate Negative phase: warmer SSTs in east equatorial ocean Change Chicago May 21 -23 2012

Eurasian winter snow cover n n Blanford (1884) first identified adverse impact of heavy winter snow cover on subsequent monsoon rains Sir Gilbert Walker used snow cover as one of the important parameters Barnett et al (1989) simulated snow/monsoon adverse relationship using climate models In general, heavier snow cover produces weaker monsoon and vice-versa Heartland Conference on Climate Change Chicago May 21 -23 2012

This jet (peak winds ~100 knots at 15 km level) is due to reversal of north-south temperature gradient. The jet disappears by October. Heartland Conference on Climate Change Chicago May 21 -23 2012

Indian Monsoon Rainfall standardized values 1871 -2001 (Top) Cramer’s t-statistic for 11 -year running mean depicting decadal variability and epochs (Bottom) Indian monsoon exhibits decadal variability and is not influenced by Global Warming at this time Heartland Conference on Climate Change Chicago May 21 -23 2012

Major floods/droughts (1813 -2010) n FLOODS n 1818 (1036 mm) n 1861 (1051 mm) n n n 1874 (1033 mm) n 1878 (1039 mm) n 1892 (1050 mm) n 1894 (1032 mm) n 1916 (1034 mm) n 1917 (1079 mm) n 1933 (1042 mm) n n n 1942 (1037 mm) n 1956 (1007 mm) n n 1961 (1088 mm)—Most Severe Flood n n 1971 (1002 mm) n 1988 (1047 mm) n n n Mean 1041 mm n DROUGHTS 1823 (795 mm) 1824 (770 mm) 1832 (775 mm) 1840 (774 mm) 1844 (788 mm) 1848 (688 mm) 1851 (744 mm) 1860 (733 cm) 1864 (748 mm) 1868 (777 mm) 1877 (609 mm)—Most Severe Drought 1899 (695 mm) 1918 (661 mm) 1920 (786 mm) 1941 (785 mm) 1965 (741 mm) 1972 (708 mm) 1979 (723 mm) 1982 (788 mm) 1986 (780 mm) 1987 (739 mm) 2002 (715 mm) Heartland Conference on Climate 2009 (698 mm) Change Chicago May 21 -23 2012 Mean 739 mm

IPCC 2007: Global temperature declined between 1945 -77, present Warming since 1980 to 2005 Heartland Conference on Climate Change Chicago May 21 -23 2012

Summer Monsoon Variability: 1951 -1975 vs 1981 -2005 n n 1951 -1975 4 floods, 3 droughts Mean rainfall: 917 mm Only 8 years below normal n n n 1981 -2005 2 floods, 4 droughts Mean rainfall: 888 mm 12 years below normal 2 years close to normal Summer monsoon was stronger during 1951 -75, weaker in recent years in a warming climate Heartland Conference on Climate Change Chicago May 21 -23 2012

Drought IOD Indian Ocean Dipole Negative phase Flood IOD Indian Ocean Dipole Positive phase Heartland Conference on Climate Change Chicago May 21 -23 2012

Severe Drought Heartland Conference on Climate Change Chicago May 21 -23 2012

Floods in Pakistan and NW India Heartland Conference on Climate Change Chicago May 21 -23 2012

Summary & Conclusions n n n Indian Monsoon is a robust system and its inter-annual variability is governed by large-scale atmosphere-ocean patterns. Droughts/floods have occurred irregularly throughout a 200 -year long dataset. Indian Monsoon appears to exhibit a decadal variability with approximately 30 -year period of above/below rainfall. Indian (and by extension Asian) monsoon is NOT impacted at this time by the modest warming of the earth’s climate. Indian and global monsoon circulations have weakened, in general, in the last 30 years or so. A conceptual drought/flood model of Indian Monsoon based on selected large-scale indices can help predict future droughts and floods with a lead time of few weeks Heartland Conference on Climate Change Chicago May 21 -23 2012