Why You Can Bet On Deadly Heatwaves During The Pre-Monsoon Months

El Niño may not come, but that’s no reason to rest easy.

15/03/2017 7:39 PM IST | Updated 05/04/2017 9:14 AM IST
STR New / Reuters

A Danish adage says that prediction is hazardous, especially about the future (erroneously attributed to Yogi Berra). But 'tis the season for predictions and climate prediction models are beginning to tend towards an El Niño for the fall and winter months of 2017 and early 2018.

As is painfully obvious by now, El Niños tend to bring a drought in the monsoon season. But El Niño forecasts tend to be less reliable during the spring months of March-April-May due to the so-called Spring Predictability Barrier which refers to the tendency of the climate system to be highly unpredictable during spring. But Nandini Ramesh and I had reported a few years ago that the onset of an El Niño starts with the discharge of the built-up warm water in the western Pacific, and this discharge actually occurs during the summer of the year before the El Niño year. This indicator not only gives us something to watch for over a year so that we can hedge our bets on early El Niño forecasts, but also is independent of what flavour of El Niño may evolve.

Only about 50% of the monsoon droughts are explained by El Niño.

El Niño has two main varieties—an Eastern Pacific type and a Central Pacific type. The latter tends to be more devastating for the Indian monsoon. Models are not skilful as of now in predicting which type of El Niño may occur. Years 2012 and 2014 were also predicted to be El Niños but they eventually fizzled out. Monsoon droughts occurred nonetheless, reminding us once again that only about 50% of the monsoon droughts are explained by El Niño. Planning the year for water resource management and food production in India is thus a monumental challenge, especially when we throw in the growing weather extremes due to global warming.

I just looked at the discharge indicator for 2016 and, fortunately, it does not appear that the warm water discharge was initiated last summer. This means one can discount the El Niño forecasts as of now, even though the impact of global warming on El Niño remains the wild card in the climate deck. We may thus avoid the misfortune of having another drought this year which would be good news indeed considering the back-to-back droughts of 2014 and 2015 and a lacklustre monsoon of 2016. Even though the All India Monsoon Rainfall got a pass grade last year, many parts of the country experienced rainfall deficits of well over 10%, which qualifies as a drought. With the weak monsoon during 2014-15, large parts of peninsular India—i.e. Kerala, Karnataka, Maharashtra and Tamil Nadu—have been parched for several years now.

As the sun moves north from the Tropic of Capricorn (starting in January) and the scorching summer heat kicks up over India a bit later during the pre-monsoon months, the multiyear droughts spell real bad news in terms of heatwaves. The pre-monsoon months are critical for farmers because they have to start cleaning off the debris and preparing the land for the monsoon sowing. The combination of the peak annual temperatures and extended outdoors drudgery make for the worst vulnerability for heat strokes and high morbidity and mortality due to heatwaves. Prior droughts and a lack of vegetation and soil moisture exacerbate the heatwaves even if there is no impending drought in the current year.

Planning the year for water resource management and food production in India is a monumental challenge, especially when we throw in the growing weather extremes due to global warming.

While the forecasts from IMD have gotten more and more reliable for the monsoon onset, active and break spells at days to weeks, and seasonal total rainfall, these are not being combined as effectively as possible to consider past droughts and present forecasts to issue longer lead heatwave outlooks. Such outlooks need not have very high skill since they are essentially no-regret outlooks. In other words, people can be advised to take precautions without causing any deleterious effects on their farm work and other livelihood. It will serve an even more important purpose of protecting the very young and the very old from being exposed to heatwaves.

It is clear that many elderly in certain parts of India consider the failure of monsoon during May and June as a danger signal for their health, some even assuming that they will not make it past this the season! But it may be too late by then to protect them from the dangerous combination of the heatwaves and a dry monsoon. But earlier outlooks may allow talukas, districts, and states to develop heatwave mitigation and adaptation strategies. This is one of the most urgent climate actions needed considering that the weather extremes are expected to continue to ramp up with global warming and the climate vulnerability remains inexcusably high in many parts of India, disproportionately affecting the poor due to the lack of access to air-conditioning, or shelters like offices and movie theatres. It is particularly alarming since the Indian rural regions, rather counterintuitively, experience higher heat island effect than the urban centres during the daytime of the pre-monsoon months.

All the forecast tools are in place to make longer lead heatwave outlooks possible. Implementation will hopefully occur pronto.

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