Rising temperatures are pushing up the frequency of incidents of extreme rainfall and India needs to be prepared for the consequences
The unexpectedly early and powerful rains over Northwest India have killed over 130 people and left 70,000 pilgrims stranded, damaged temple towns, and washed away roads and 21 bridges in Uttarakhand. And we still don’t know the extent of deaths, injuries and damage because of the impaired connectivity.
In climate literature, rainfall more than 150 mm in a day is termed a very heavy rain event. Dehradun “on Monday morning registered a record rainfall of 340 mm. This amount of rain in June is seen almost after five decades,” said the regional director of the India Meteorological Department (IMD) (The Hindu, June 18, 2013). The unfolding disaster raises two questions: is this extreme rainfall due to global warming? And what issues does it flag?
A study by scientists at the National Atmospheric Research Laboratory, Tirupati, showed a six per cent increase in the frequency of very heavy rain events in India over 1901-2004. The more recent period 1951-2004 shows a 14.5 per cent rise per decade. They lay this at global warming’s door: the study talked of a “coherent relationship” between the increasing trend of extreme rainfall events in the last five decades and the increasing trend of Indian Ocean sea surface temperature (M. Rajeevan et al, “Analysis of Variability and Trends of Extreme Rainfall Events Over India Using 104 Years of Gridded Daily Rainfall Data,” Geophysical Research Letters, 35, September 2008). Another school of thought emphasises regional rather than global factors. For instance, Subimal Ghosh et al found an increase in the geographical spread of rainfall extremes in India, but emphasised urbanisation, deforestation and other changes in land use more as causal factors (“Lack of Uniform Trends but Increasing Spatial Variability in Observed Indian Rainfall Extremes,” Nature Climate Change, 18 December 2011).
Single events and climate
Neither argument seeks to connect single rainfall events to global warming. It is in the nature of its methodology that it is not possible to ascribe single rainfall events to climate change. Climate change is a trend over time. However, as extreme events become more frequent in the world, some scientists are trying to grapple with this problem. One group tweaked the question a bit. They have argued that certain recent extreme events — the heatwaves and droughts in Moscow in 2010, and Texas, Oklahoma and northern Mexico in 2011 – were a consequence of global warming “because their likelihood in the absence of global warming was exceedingly small” (James Hansen et al, ‘Perception of Climate Change’, PNAS, 6 August 2012, pp. 2415-2423). Hansen et al showed that extreme temperatures exceeding 3-sigma (a measure of variability and volatility), which covered only 0.1-0.2 per cent of the Earth’s land area in the 30-year period 1950-1980, occurred in as much as 10 per cent of the planet’s land mass in recent summers. Would the heatwaves they refer to have happened in the absence of this huge spread of extreme warming? No.
But note that even this study is largely linking specific temperature anomalies to global warming, not rainfall events. I believe that this methodological impossibility in ascribing single rainfall events, however extreme, to climate change, bolsters the already prevalent complacency about climate change in Indian officialdom and even the denial of global warming.
The picture changes when one considers recent trends. Extreme rainfall events are spreading in India. The Uttarakhand State Action Plan on Climate Change admits to a “few high rainfall events in the recent past” (Govt. of Uttarakhand, SAPCC Revised Version, June 2012, p. 24). People consulted did report erratic rains and increased frequency of intense rainfall events (p.27). There’s no doubt in my mind that this increasing variability and intense downpours are a consequence of global warming, due to the capacity of warmer air to hold more water vapour. It happened last year in Uttarkashi, it’s occurred this year again. It’s going to continue to happen, frequently.
This raises three issues. Surely adaptation means not just desperate rescue during and after extreme rains, but preparing for them. Experts suggest prior warning systems are feasible, with reasonable investment. Given there was no warning from the IMD, what technological or administrative improvement do we need to ensure that advance warnings are issued before such future events? Two, that needs not just technology but political will. We need to collectively challenge the callous indifference that most political elites have for the lives and livelihoods of the poor. And three, even assuming a best-case scenario of capacity, efficiency and political will, what impacts and devastation are inescapable in a difficult and mountainous terrain? What we are currently experiencing is in a world 0.9°C warmer than pre-industrial temperatures. Due to the lag between carbon emissions and global warming, a significantly warmer world is inevitable, as are more extreme events. What has happened this year is going to happen, again, often, and more intensely.
(Nagraj Adve, an activist based in Delhi, works on issues connected with global warming. E-mail: email@example.com)