Air Pollution And Irrigation Mask The Extremes Of India’s 2019 Heatwave

Air Pollution And Irrigation Mask The Extremes Of India’s 2019 Heatwave

Farmer working on irrigation dykes, Uttar Pradesh, India. Credit: Purepix / Alamy Stock Photo

India is currently suffering one of the longest heatwaves in its recent history. Northern and central parts of the country have seen intense heat for more than 30 consecutive days, with temperatures in New Delhi topping 48C – the highest ever recorded in the capital in June.

Such an extended period of ferocious heat has been deadly. In the eastern state of Bihar, for example, 180 people have so far died, with hospitals “inundated with people suffering from heatstroke”.

The extreme weather follows in the footsteps of a lethal heatwave in 2016, when India recorded its highest-ever temperature of 51C in the western state of Rajasthan – one of the hottest temperatures ever recorded on earth.

Globally, the frequency and intensity of heatwaves are generally rising due to climate change. However, we do not yet see a clear upward trend in extreme temperatures in India.

A complex mix of competing human impacts means that, despite rising average temperatures, maximum temperatures have not risen in tandem. This article looks at the data, explains the (lack of a) trend and looks at the rising risks in store for the future.

Defining a heatwave

For India, May to June is typically the hottest period of the year, with temperatures often reaching up to 40C in the hottest areas before the cooling southwest monsoon rains arrive in July.

However, this year was worse than usual. As the map below shows, maximum temperatures reached well above 40C across most of India – and even into Pakistan.

Air Pollution And Irrigation Mask The Extremes Of India’s 2019 Heatwave

Map showing highest daily maximum temperature of the year 2019, based on data from ECMWF operational analyses and forecasts up to 27 June 2019. Red shading indicates the hottest temperatures, note that the colours start at 40C. Produced by Geert Jan Oldenborgh via the KNMI Climate Explorer.

Although it is easy to define and monitor when and where local record temperatures are broken, a heatwave is less straightforward as there are different metrics available.

Focusing on the one-day maximum temperature can be most relevant for rural outdoor workers, who are among the most vulnerable to heatwaves in India. A focus on longer durations, say three days, may better capture the impacts on urban populations and indoor workers. There are also heatwave indices that account for factors beyond temperature, notably humidity, which is known to play an important role in how heat impacts the human body.

Nevertheless, in a warming climate we expect heat records to be broken more frequently and for heatwaves to become more intense. We see this in many parts of the world, with rising intensity and frequency of heatwaves attributed to human-caused climate change.

This includes the famous 2003 heatwave in Europe, responsible for more than 70,000 deaths, which was the first event where scientists were able to identify a human influence. The likelihood of this event had more than doubled due to climate change. (It has continued to increase since then.)

While it might be expected that the dominant impact of global warming would extend to India, there are a number of other important factors that affect maximum temperatures locally.

Worsening air pollution blocks more and more sunlight and, thus, decreases maximum temperatures. In addition, increasing irrigation means that more of the heat is used to evaporate water and less to warm the air.

Finally, while in many big cities the “urban heat island” effect leads to hotter heat waves, some cities in the dry north of India actually show an “urban cool island” effect driven by higher water usage compared to the surrounding arid land areas.

Taken together, these factors play as large a role as global warming and counteract the expected upward trend in heatwaves – at least for now.

Competing impacts

To investigate how all these factors affect heatwaves we need reliable observations. For India, these are not easy to obtain.

Publicly accessible global datasets often have large amounts of missing data over India. Worse, the amount of missing data in the 1970s was so high that many heatwaves were likely not recorded in those years. This leads to an artificial upward trend after the 1970s as the number and quality of weather measurements improved.

An alternative option is to use temperature records based on a combination of direct measurements and a weather model – an approach known as “reanalysis”. While these are not perfect, they are presently the best publicly available basis to study real-world occurrences of heatwaves.

Analysing both the observations (corrected for missing data) and reanalyses, we find no trend in the highest maximum temperatures of the year over most of India since the 1970s. This holds for heatwave definitions from single hot days to weekly averages and even for the monthly average of maximum temperatures in May and June.

The chart below shows the highest daily maximum temperature of the year, as an average over India, over the past 40 years (red line). The green line shows a slightly declining trend over that time.

Overall, maximum temperatures in the hottest months do not tend to show an increasing trend across India. Instead, the high temperatures of 2019 seem due to the natural year-to-year variability of the weather.

Air Pollution And Irrigation Mask The Extremes Of India’s 2019 Heatwave

Average over India of the highest daily maximum temperature of the year (ERA-interim extended with operational analyses and forecasts up to 30 June 2019). Produced by Geert Jan Oldenborgh.

Our analysis suggests that the combination of increased air pollution and irrigation have more or less offset the warming from increased greenhouse gases.

So, how do we know this?

Well, while maximum temperatures have not increased, minimum temperatures have. As daily minimum temperatures typically occur at night, they are much less affected by air pollution (which primarily affects incoming solar radiation).

And, indeed, we see that the hottest nights of the year have increased since the 1970s over large parts of India. This means that, overall, average temperatures have continued to rise. The chart below shows the highest daily average temperatures averaged over India for the past 40 years (red line). The green line shows a small increasing trend.

Air Pollution And Irrigation Mask The Extremes Of India’s 2019 Heatwave

Average over India of the highest daily average temperature of the year (ERA-interim extended with operational analyses and forecasts up to 27 June 2019). Produced by Geert Jan Oldenborgh via the KNMI Climate Explorer.

In addition, relative humidity in May has increased strongly since the 1970s, probably due in part to irrigation. Therefore, despite the fact that there is no clear increase in maximum temperature extremes, heat indices that take humidity into account do show upward trends: heatwaves have become more humid, posing greater risk to human health. Increased air pollution also substantially increases the negative health impacts of heatwaves, but as far as we know this has not yet been quantified.

The conclusion is that the meteorological heatwaves described by the highest one-day – and multiple-day – maximum temperature trends have not increased in intensity over India since the 1970s, contrary to most of the rest of the world.

And, so, while the current heat in 2019 is more severe than in the last few years, this is not yet part of a clear systematic trend. But health impacts of heatwaves have been getting more severe due to higher humidity and more air pollution.

Expected trends

For the future, we expect that a clear signal of human-caused climate change to emerge in maximum temperatures as measures are put in place in India to improve air quality.

A similar effect was seen in western Europe where summers only became hotter from the mid-1980s onwards when emission of pollutants was successfully regulated and reduced.

In addition, with expanding groundwater depletion, keeping up the present-day irrigation rates could prove challenging for parts of India. Thus, both factors currently counteracting the impacts of global warming on Indian heat extremes are likely to change.

Given that greenhouse gas concentrations continue to increase, we expect to see an amplified upward trend in heatwaves in the not too distant future.

It is important to note that climate models typically do not include the effects of irrigation and are sometimes limited in how they represent air pollution. More research – including better model representation of these factors – is, therefore, needed to better quantify the different drivers of heat extremes and more reliably assess future heatwave risks.

Adaptation

The impacts of heatwaves also strongly depend on vulnerability and exposure of people and the systems they rely on.

On the one hand, these factors can also contribute to the rising risk of heatwaves, but they may also offer opportunities to better manage those risks, even in the face of increasing heat.

The extent to which people have to work outside and the availability of clean water – and sometimes even air-conditioning – can make an immense difference for reducing heat deaths and hospital admissions.

Advice to vulnerable groups on behaviour during periods of heat – such as drinking enough water – and sometimes even government regulation – for instance, prohibiting outside labour during the hottest hours – can also have an enormous impact. Over the longer run, urban design, including housing but also urban green space, also needs to take more account of rising heat risks.

In France, the “Plan Canicule” initiated after the deadly 2003 heatwave has very significantly reduced excess deaths in similar heatwaves, In India, the “Heat Action Plan” implemented in the city of Ahmedabad have been shown to have drastically reduced mortality during the heatwave of 2015. Yet many cities do not yet have such plans and many countries don’t even have heatwave early warnings, despite excellent predictability and the rising risks.

In the long-term, the projected increases in heat and humidity will require much more efforts to better manage the rising risk of heatwaves. If global warming continues unabated, it could challenge the ability for humans, livestock and wildlife to survive outdoors in parts of India.

This article originally appeared on CarbonBrief

About The Author

Dr Geert Jan van Oldenborgh, Dr Gabriel Vecchi, Dr Flavio Lehner, Dr Friederike Otto, Dr Karsten Haustein, Dr Claudia Tebaldi, Dr Maarten van Aalst and Dr Krishna AchutaRao are from the World Weather Attribution collaboration.

Related Books

Climate Change: What Everyone Needs to Know

by Joseph Romm
0190866101The essential primer on what will be the defining issue of our time, Climate Change: What Everyone Needs to Know® is a clear-eyed overview of the science, conflicts, and implications of our warming planet. From Joseph Romm, Chief Science Advisor for National Geographic's Years of Living Dangerously series and one of Rolling Stone's "100 people who are changing America," Climate Change offers user-friendly, scientifically rigorous answers to the most difficult (and commonly politicized) questions surrounding what climatologist Lonnie Thompson has deemed "a clear and present danger to civilization.". Available On Amazon

Climate Change: The Science of Global Warming and Our Energy Future second edition Edition

by Jason Smerdon
0231172834This second edition of Climate Change is an accessible and comprehensive guide to the science behind global warming. Exquisitely illustrated, the text is geared toward students at a variety of levels. Edmond A. Mathez and Jason E. Smerdon provide a broad, informative introduction to the science that underlies our understanding of the climate system and the effects of human activity on the warming of our planet.Mathez and Smerdon describe the roles that the atmosphere and ocean play in our climate, introduce the concept of radiation balance, and explain climate changes that occurred in the past. They also detail the human activities that influence the climate, such as greenhouse gas and aerosol emissions and deforestation, as well as the effects of natural phenomena.  Available On Amazon

The Science of Climate Change: A Hands-On Course

by Blair Lee, Alina Bachmann
194747300XThe Science of Climate Change: A Hands-On Course uses text and eighteen hands-on activities to explain and teach the science of global warming and climate change, how humans are responsible, and what can be done to slow or stop the rate of global warming and climate change. This book is a complete, comprehensive guide to an essential environmental topic. Subjects covered in this book include: how molecules transfer energy from the sun to warm the atmosphere, greenhouse gases, the greenhouse effect, global warming, the Industrial Revolution, the combustion reaction, feedback loops, the relationship between weather and climate, climate change, carbon sinks, extinction, carbon footprint, recycling, and alternative energy. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

 

YOU MAY ALSO LIKE

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook icontwitter iconyoutube iconinstagram iconpintrest iconrss icon

 Get The Latest By Email

Weekly Magazine Daily Inspiration

EVIDENCE

image
Matt Canavan suggested the cold snap means global warming isn't real. We bust this and 2 other climate myths
by Nerilie Abram, Professor; ARC Future Fellow; Chief Investigator for the ARC Centre of Excellence for Climate Extremes; Deputy Director for the Australian Centre for Excellence in Antarctic Science, Australian National University
Senator Matt Canavan sent many eyeballs rolling yesterday when he tweeted photos of snowy scenes in regional New South…
Ecosystem sentinels sound alarm for the oceans
by Tim Radford
Sea birds are known as ecosystem sentinels, warning of marine loss. As their numbers fall, so could the riches of the…
Why Sea Otters Are Climate Warriors
Why Sea Otters Are Climate Warriors
by Zak Smith
In addition to being one of the cutest animals on the planet, sea otters help maintain healthy, carbon-absorbing kelp…
Methane Bubbles From The Seafloor Hint At Offshore Quakes To Come
Methane Bubbles From The Seafloor Hint At Offshore Quakes To Come
by Hannah Hickey
Methane bubbles that squeeze out of sediment and rise from the seafloor off the coast of Washington provide important…
Why is the Arctic warming faster than other parts of the world?
Why is the Arctic warming faster than other parts of the world?
by Steve Turton, Adjunct Professor of Environmental Geography, CQUniversity Australia
What is Arctic amplification? Do we know what is causing this phenomenon? What effects is it having, both in the region…
bird flies over water
Seabirds are today's canaries in the coal mine – and they're sending us an urgent message
by David Schoeman, Professor of Global-Change Ecology, University of the Sunshine Coast
Just as caged canaries once warned coal miners of the risk of carbon monoxide poisoning, free-flying seabirds are now…
yv27nbnoz3
Why Fires Burning Higher In The Mountains Are A Clear Sign Of Climate Change
by Mojtaba Sadegh, Boise State University et al
The Western U.S. appears headed for another dangerous fire season, and a new study shows that even high mountain areas…
Almost All The World’s Glaciers Are Shrinking—and Fast
Almost All The World’s Glaciers Are Shrinking—and Fast
by Peter Rüegg, ETH Zurich
A new study shows just how fast glaciers have lost thickness and mass over the past two decades.

LATEST VIDEOS

The Great Climate Migration Has Begun
The Great Climate Migration Has Begun
by Super User
The climate crisis is forcing thousands around the world to flee as their homes become increasingly uninhabitable.
The Last Ice Age Tells Us Why We Need To Care About A 2℃ Change In Temperature
The Last Ice Age Tells Us Why We Need To Care About A 2℃ Change In Temperature
by Alan N Williams, et al
The latest report from the Intergovernmental Panel on Climate Change (IPCC) states that without a substantial decrease…
Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get?
Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get?
by Toby Tyrrell
It took evolution 3 or 4 billion years to produce Homo sapiens. If the climate had completely failed just once in that…
How Mapping The Weather 12,000 Years Ago Can Help Predict Future Climate Change
How Mapping The Weather 12,000 Years Ago Can Help Predict Future Climate Change
by Brice Rea
The end of the last ice age, around 12,000 years ago, was characterised by a final cold phase called the Younger Dryas.…
The Caspian Sea Is Set To Fall By 9 Metres Or More This Century
The Caspian Sea Is Set To Fall By 9 Metres Or More This Century
by Frank Wesselingh and Matteo Lattuada
Imagine you are on the coast, looking out to sea. In front of you lies 100 metres of barren sand that looks like a…
Venus Was Once More Earth-like, But Climate Change Made It Uninhabitable
Venus Was Once More Earth-like, But Climate Change Made It Uninhabitable
by Richard Ernst
We can learn a lot about climate change from Venus, our sister planet. Venus currently has a surface temperature of…
Five Climate Disbeliefs: A Crash Course In Climate Misinformation
The Five Climate Disbeliefs: A Crash Course In Climate Misinformation
by John Cook
This video is a crash course in climate misinformation, summarizing the key arguments used to cast doubt on the reality…
The Arctic Hasn't Been This Warm For 3 Million Years and That Means Big Changes For The Planet
The Arctic Hasn't Been This Warm For 3 Million Years and That Means Big Changes For The Planet
by Julie Brigham-Grette and Steve Petsch
Every year, sea ice cover in the Arctic Ocean shrinks to a low point in mid-September. This year it measures just 1.44…

LATEST ARTICLES

image
Why the UK is so unprepared for the impacts of climate change
by Liam F. Beiser-McGrath, Lecturer (Assistant Professor) in Politics and Director of the PECC Lab, Royal Holloway University of London
The UK is woefully unprepared for the dangers of climate change according to a report from the Climate Change Committee…
Rows of solar panels are separated by a walkable space between them
Solar power and energy storage combo boosts reliability
by Matt Shipman-NC State
New research shows that when a power system combines energy storage and solar power generation, the end result is…
Climate change: what G7 leaders could have said – but didn't
Climate change: what G7 leaders could have said – but didn't
by Myles Allen, Professor of Geosystem Science, Director of Oxford Net Zero, University of Oxford
The four-day G7 summit in Cornwall ended with little cause for celebration from anyone worried about climate change.…
How world leaders' high-carbon travel choices could delay climate action
How world leaders' high-carbon travel choices could delay climate action
by Steve Westlake, PhD Candidate, Environmental Leadership, Cardiff University
When UK prime minister Boris Johnson took a one-hour flight to Cornwall for the G7 summit, he was criticised for being…
Maggot burgers can help to solve world hunger
by Paul Brown
Fancy maggot burgers for dinner? Eating animals and plants which revolt many of us could cut hunger caused by climate…
The idea of green growth'is flawed. We must find ways of using and wasting less energy
by Michael (Mike) Joy, Senior Researcher; Institute for Governance and Policy Studies, Te Herenga Waka — Victoria University of Wellington
As countries explore ways of decarbonising their economies, the mantra of “green growth” risks trapping us in a spiral…
Four reasons why G7 climate finance initiative will struggle against China's Belt and Road
Four reasons why G7 climate finance initiative will struggle against China's Belt and Road
by Karen Jackson, Senior Lecturer in Economics, University of Westminster
During the G7 summit in Cornwall, the group of nations unveiled a global initiative to help low and middle-income…
image
Electric heat pumps use much less energy than furnaces, and can cool houses too – here's how they work
by Robert Brecha, Professor of Sustainability, University of Dayton
To help curb climate change, President Biden has set a goal of lowering U.S. greenhouse gas emissions 50%-52% below…

 Get The Latest By Email

Weekly Magazine Daily Inspiration

New Attitudes - New Possibilities

InnerSelf.comClimateImpactNews.com | InnerPower.net
MightyNatural.com | WholisticPolitics.com | InnerSelf Market
Copyright ©1985 - 2021 InnerSelf Publications. All Rights Reserved.