Many extreme weather events can be attributed to climate change with a greater degree of certainty, but in India attribution science is still in a nascent stage
The first eight months of 2019 have been remarkable for one reason: Not a single month has passed without an extreme weather event in India or in the world. Union Minister for Environment, Forest and Climate Change Prakash Javadekar in a recent public meeting in Pune flatly denied the role of climate change in the country’s current spell of extreme rainfall events and floods.
Elsewhere, scientists have been bringing out studies one after another attributing the never-seen-before climate anomalies to climate change.
Since 2009, every year scientists have declared record-breaking climate events. The pertinent question to be asked now is if climate change is responsible for the extreme weather events of the past 10 years? And if it is, how can one quantify this responsibility? Is there any way one can identify if a particular extreme weather event occurred only because of climate change?
The developing science of attribution might have some answers but not all of them. Scientists say when it comes to climate, sure shot predictions cannot be made.
“Such certain conclusions are not possible because weather is not a perfectly predictable system. Conclusions of attribution science are almost always probabilistic,” said Arpita Mondal, assistant professor at Indian Institute of Technology, Bombay and an expert in attribution science.
Scientists are of the view that attribution works with probabilities and there are certain extreme weather events that can be attributed to climate change with a greater degree of certainty.
“The heat waves of 2015 and 2016 have been attributed to global warming, particularly when considering a combination of temperature and humidity,” said Mondal.
“Attribution analysis of the heavy rainfall in Chennai in December 2015 does not reveal enough evidence to say with certainty that greenhouse gas-related warming played a significant role,” she added.
Moreover, she points out that getting detailed climatic data — the kind required by attribution science — for certain events, especially hydrological weather events in India, is difficult. This shows that attribution science in India is still in its nascent stage.
The Indian government does not come out with scientific reports to attribute the extreme weather events to climate change, though India Meteorological Department (IMD) does mention these events in its annual climate summary.
In many of these summaries that IMD has compiled from 2009 to 2017, there are certain discrepancies and ambiguous presentation of data on extreme weather events.
Apart from the reports of the initial years, cyclones and droughts or dry spells have not been counted as extreme weather events. For example, in July 2015, Cyclone Komen had struck parts of West Bengal, Odisha and Manipur and killed around 100 people. But this cyclone has not been mentioned as an extreme event in IMD’s annual climate summary for 2015.
This is when two deep depressions, one in Gujarat in June and another in Tamil Nadu in November, were accounted for by the report. The only cyclones mentioned in the climate summaries of the last 10 years are Thane in 2011 and Nilam in 2012.
Similar is the case with droughts. Though for some of the years, some regions across the country have suffered from moderate to severe drought throughout the year, the damages caused are not mentioned.
Drought has been highlighted only once in the 2009 climate summary, where it was mentioned that 46 per cent of the country was either under moderate or severe drought conditions.
Another ambiguity in these reports is in the consideration of lightning as part of storm activity (thunder/dust/hail). Lightning does not occur on its own and is accompanied by storms, even if minor. In some of the reports storms and lightning are mentioned separately and in others they are clubbed together.
For researchers looking at data for scientific attribution, these ambiguities can be a major roadblock. Knowing what exactly constitutes extreme weather and removing any discrepancies would go a long way in generating data about them and also aid scientists who are trying to study them in the context of climate change. This is when IMD is the only institution in India that collects weather-related data.
Many other countries have taken significant steps in the direction of attributing extreme weather events occurring in their respective territories to climate change. For example, the Oxford University and United Kingdom Meteorological Office have several studies on attribution of extreme weather events (such as heat waves, floods and droughts) in the UK.
They have also collaborated and worked on droughts in Africa, or heat waves and heavy rainfall in India. The University of Melbourne has carried out some detection and attribution studies on heat waves and droughts in Australia.
The National Academy of Sciences in the US has brought out a special report on attribution. Germany is also going to use “operational attribution” studies to deal with climate change.
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