As the UN Climate summit comes to a close without setting a realistic target to limit global emissions, and Chennai – and alarmingly, Bengaluru – realise how close to home the threat of global warming is, C.B. Ramkumar, our resident ‘green warrior’ sounds the alarm.
December 1, 2015 will be etched into the weather history books in Chennai for the heaviest rainfall it received in a hundred years, 490mm in a single day. November 2015 will be etched into the weather history books in Bengaluru as it received 290.44 mm of rainfall, the highest in 100 years during the North east monsoon surpassing the all-time high monthly rainfall record that stands at 252.2 mm. Not only this, city has also exceeded seasonal average rainfall of 226.1 mm that comprises of October, November and December.
The heavy rainfall in Chennai forced the government to release 30,000 cusecs of water from the Chembarambakkam reservoir. As a result of this release, which officials have insisted was necessary to ensure that the reservoir remained safe, the Adyar River was in spate. A notification from the government on the release of water could have prevented loss of lives, as people could have been moved out in time. But then who was thinking straight, leave alone planning ahead!
Most parts of the southern and even central parts of the city were flooded. Chennai has seen regular flooding of its southern parts during winter, but what it had not seen was the flooding of the heart of the city. Enough has been said and written about the unplanned real estate boom in the last decade. Citizens read every day news articles about how layouts, housing colonies, shopping malls and office blocks have sprung up on the wetlands, water bodies and low level areas. Now everyone is looking helplessly at the follies of the last decade. Add to this the lack of an extensive and effective storm water drain, and you have a never-seen-before situation in Chennai.
The November rainfall in Bengaluru did not cause damage, relative to what happened in Chennai. Some flooding of low lying areas, electricity being shut down for brief periods of time, day 2 of the second test match between India and South Africa cancelled, and chilly weather.
There is immense debate in weather circles about the role that El Nino, the oceanic-atmospheric phenomenon where sea surface temperatures of East Pacific Ocean warm up, in the extreme weather conditions that Chennai and Bangalore witnessed. Some say it is the El Nino effect. Prof Bhanu Kumar, Head of the Department of Meteorology and Oceanography in Andhra University, blames the heavy rainfall on the El Nino effect. Skymet Meteorology Division in India, concurs with him and says that these extremely heavy spells of rain have a strong relation to El Nino.
Others like B. Mukhopadhyay, Additional Director General of Meteorology Research, IMD Pune do not feel it is the El Nino effect. He feels that El Nino affects whole seasons and not one off instances of rainfall. “An individual episode like that on December 1 is a combination of several factors and in every such episode, the combination changes. On December 1, the lower-level moisture supply was high and upper air evacuation of the moisture was also strong. We call this phenomenon upper air divergence, and the effect is that the cloud becomes very intense. Both coincide very rarely,” he said.
Our Environment Minister thinks that the extreme weather has nothing to do with El Nino or Climate Change and it is just a natural calamity, “What has happened in Chennai over last ten days is absolutely a very serious situation, this can’t be directly attributed to climate change; it is a natural calamity, but this calamity needs to be tackled effectively,”.
What are we to make of all this? Weather experts don’t seem to concur, so how do we process all these extreme weather incidences so close to home. When in doubt, go back to science. While the Chennai and Bengaluru rainfall was certainly breaking news, from a climate change perspective, I term it as hot news, as it is a result of warming of the planet.
Let’s get down to the basics. Planet earth is getting warmer because of human activity. We are producing huge quantities of green house gases (GHGs) which is making the atmospheric layer thicker, resulting in more infrared waves from the sun getting trapped within the Earth’s atmosphere, instead of getting reflected back into space. So what does this have t do with the rain fall events?
Oceans cover 71% of planet earth. 90% of the extra heat trapped by manmade global warming goes into the ocean. Cheryl Katz, a San Francisco Bay Area-based science writer covering energy, environmental health, and climate change reports, says that the ocean has been heating at an alarming rate over the past decade, amassing energy the equivalent of roughly five Hiroshima bombs exploding every second since 1990. Overall, the world’s oceans are warmer now than at any point in the last 50 years and the top layer is now getting warmer at a rate of 0.2°F per decade. So what?
The devastating effect of warmer oceans is that it causes powerful storms. Storms gain energy from warm oceans, so what may start off like a small storm system intensifies to become a large more powerful storm, if the path of the storm has warm oceans.
Hurricane Sandy that struck the North East of the United States of America on 29th October 2012, was testimony of how warm oceans energise storms, making them bigger and deadlier. The waters on the pathway of Hurricane Sandy were warmer than usual. Typhoon Haiyan that struck Philippines on 10th November 2013 is another example. Scientists tracking the path of Typhoon Haiyan were able to conclude that the waters were much warmer, making it a deadly typhoon killing over 6,500 people. With sustained wind speeds of more than 310 km per hour, Haiyan was the most powerful tropical cyclone to make landfall in recorded history.
Warm air also adds other factors to the normal hydrological cycle. Warmer air can hold much more water vapour, and with each additional 1° (C) of temperature, the atmosphere’s capacity to hold water vapour increases by 7% . There is already 4% more water vapour over the oceans than there was only 30 years ago. So what does all this result in? The downpours are becoming bigger, resulting in record rainfall like the 490 mm in Chennai and the 290 mm in Bengaluru.
We have had more extreme weather events in the last two decades than ever. The science is clear about the extreme weather events that are hitting us regularly. This year, the El Nino has been extremely strong – the most in over 18 years – and coupled with unusually-cold sea-surface waters near the Tamil Nadu and Kerala coast, has gravitated extra gusts towards Chennai, says Mahesh Palawat, Chief Meteorologist, Skymet Weather. October 2015 was the hottest October on record over the past 136 years, according to a report from the US National Oceanic and Atmospheric Administration (NOAA).
At the same time, 2015 is on course to being the hottest-ever year recorded both globally, as was recently confirmed by the IMD. The same holds for ocean temperature. The United States’ National Oceanic and Atmospheric Administration has established that the Indian Ocean’s temperature in October 2015 was the record hottest. Warn oceans make small storms mega storms, and this is what we saw in Chennai and Bengaluru.
The good news is that Chennai is recovering, and Bengaluru is trying to learn from Chennai’s urban planning mistakes. The bad news is that the worst may not be over as yet, as the cyclical effect El Nino 2015 and cumulative effects of decades of green house gas emissions will force us to see even bigger storms. I am praying that I am wrong.
(The writer is MD, Green Dreams for the Planet. He can be contacted at www.CBRamkumar.com or www.GreenDreams.Vision)
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