Are rising heat and humidity fuelling deaths by lightning?

Recent research suggests that extreme heat waves and high atmospheric humidity could be triggering increased lightning strikes in regions that are most vulnerable to climate change
Dark clouds had formed, heading in their direction, the dramatic zigzags across the sky getting closer, but not a drop of rain had fallen yet. This only added to the teenagers’ thrill, determined to play the fiercely competitive rural cricket tournament’s last match. When the first lightning flashed barely 160 feet overhead, of the 22 teenagers, six ran into a roofless, half-constructed building. The second bolt caught them clinging to each other terrified. Death from massive cardiac arrests was instantaneous, the doctor said.

The six deaths are among close to 300 lightning deaths in Odisha from March to early September this year, while the two previous years recorded 401 deaths in 2016 and 398 in 2015. The death graph is seen steadily climbing from 183 fatalities in 2001, according to Odisha State Disaster Management Authority (OSDMA) data.

Loss of life due to lightning has remained the highest of all natural calamities over the last decade in Odisha, one of India’s most disaster-prone states. Deaths from extreme weather events in 2015 indicate the trend in Odisha, where flood deaths were eight, heat stroke deaths were 60 and lightning deaths were 398, according to the Special Relief Commissioner’s office. Even Category 4 cyclone Hudhud’s toll could be contained at three, while fatalities from severe floods remain below 10 between 2015 and 2017.

Lightning fatalities

Close to 20% of national lightning fatalities, which vary from 2,000 to 2,500, are from Odisha. West Bengal, Assam, Bihar, Maharashtra and the Himalayan states are some other vulnerable states.

A NASA Earth Observation satellite study over 1995-2002 shows eastern Indian states, including Odisha, customarily get comparatively higher lightning strikes, which are around 20 to 30 flashes per sq. km per year. These are concentrated in the hottest pre-monsoon months, particularly in May. Lightning seems to happen more often closer to the equator because this part of the earth is the fastest to warm. Central Africa receives as high as 150 strikes per sq. km per year.

Why are lightning events increasing and is the peak hit season expanding? This is the question that has got the state to begin a study to understand the pattern of thunder squalls: their seasonal timing, favoured geographies and the strata of people most affected. It aims awareness blitzkriegs in vulnerable places after results are known.

Links with climate change

Although the jury is still out on whether climate change induced weather conditions, particularly extreme heat and high humidity are triggering increased lightning in some regions, researches, though few, are saying this is in fact what is happening.

A major 2014 US scientific study on lightning calculates that every one Celsius rise in global average air temperature would lead to an increase in the frequency of lightning strikes by 12%. By 2100, there would be a 50% rise in lightning strikes, assuming a 4 degree rise in average temperature by the end of this century. Currently, there are around 25 million lightning strikes globally every year.

The study estimates the more heat energy available to fuel storm clouds, the more energetic would they become. It also links heavy precipitation and storm energy to the amount of water vapour available in the atmosphere. A warmer atmosphere is also one with higher moisture. Essentially, more moisture suggests more vigorous thunderstorms and so more lightning, the researchers said.

Sarat Chandra Sahu, heading the India Meteorological Department (IMD) in Bhubaneswar, explains that the higher the mean day temperature, lower would be the atmospheric pressure. When clouds suck up moisture rapidly, the hotter and lighter air moves up in the cloud, causing the colder, denser and heavier cloud portions to sink. Due to such abnormal swings from high to low temperature within cloud formations, there is stronger convection or transfer of electric energy. Thunderstorms are formed.

Scientific observers point out after three very hot days, dense vertically towering storm clouds called cumulonimbus clouds are formed from water vapour carried up by powerful upward currents. Such clouds produce intense lightning, even tornadoes.

“Sufficiently available moisture, unstable air and atmospheric mechanism to lift the warm air, when available together cause thunderstorm and lightning,” Sahu told
Increased activity

According to the fourth report of the United Nations Intergovernmental Panel on Climate Change (IPCC) in 2007, an increase in lightning activity will have particular impact in areas that become warmer and drier as global warming progresses.

During El Niño years, which make air warmer and drier, there are fewer but more intense thunderstorms, with 50% more lightning activity, found researchers at Israel’s Tel Aviv University. Since 2000, El Niño events have been observed in 2002–03, 2004–05, 2006–07, 2009–10 and 2014–16.

In May 2015, an extreme heat wave in Odisha was unique in that it lasted for about two weeks in the 3rd and 4th weeks of the month. Around 12 to 15 cities in the state experienced a daily maximum temperature of over 45 degrees Celsius during this extremely abnormal heat wave period.

Researchers studying this phenomenon based on IMD data find from 2009 to 2015, the average rise in May temperature has been.0.41 degree Celsius over 1901 onward average.
Again in May 2016, three weeks were under heat wave conditions in Odisha with maximum temperature reaching 40.2 degree Celsius. All through May to August, several places in Odisha record high 75% to 95% humidity, laying a red carpet for intense lightning events.

According to IMD, 2016 was the hottest year recorded since 1901 in India. The country averaged annual mean land air temperature of 0.91 degree Celsius above the 1961-1990 average. The temperature anomaly of March to May hot weather season was 1.36 degrees Celsius above average, making it the second warmest since 1901.

More studies required

Almost all persons killed or injured by lightning in Odisha, as also elsewhere in India, belong to the economically less privileged groups and live in villages. A majority, mostly daily wage farm hands, is caught by the lightning late afternoon working in rice fields; others are herding back the cattle as the sun begins to set — the peak time for thunder squalls in Odisha. In the hot months, those too poor to afford electricity are cooling off as best as they can, under trees.

While lightning claims human lives, it does not often destroy property or livelihoods at the scale that other extreme weather events like floods, cyclones or droughts do. This is also a reason scientific researches to understand an admittedly complex phenomenon and prevent its toll, has not been urgently addressed.
Lightning is not included in the list of natural disasters under the central government’s Calamity Relief Fund (CRF). Odisha however has been compensating families of victims with INR 400,000 (USD 6,172) from its emergency funds.

Scarred survivors

Of every 10 people hit by lightning, nine will survive to tell the tale. But they could suffer a variety of short- and long-term effects after being hit by this electrical current that can approach 200 million volts and travels at one-third the speed of light. Side effects include temporary cardiac arrest, confusion, headaches, memory blips, dizziness, muscle aches, deafness, chronic pain and even personality changes like anxiety disorder. If the centre puts lightning on its calamity relief funding, compensation could be paid for long-term treatment, human injuries and animal deaths.

Since 2016, IMD Bhubaneswar has been forecasting on a daily basis the districts likely to face lightning activity.

After waiting since 2000, post the super-cyclone, in 2015 Odisha installed its first 500-km radius Doppler radar which costs INR 300 million (USD 4.63 million), ending its dependence on neighbouring Vishakhapatnam naval base. Doppler radars send out electromagnetic waves that get reflected back to the radar from water vapour and other molecules, able to carry back information on a range of weather conditions approximately five hours prior to striking time.

In Baunsamula-Jhunapada village in coastal Odisha, Sheikh Mukhtar, the youngest of the six village cricketers who dreamed to make it big some day, would have been 16 this month. His mother obsessively plants trees. “If more tall trees were standing perhaps my Mukhtar would have been spared,” she says.

Photo Caption: Most of those killed by a lightning bolt, either hit directly or when the monstrous electric current hopscotches after hitting a tree or other tall objects, are farm hands in the field busy during India’s peak rice cultivation season. 

Read original report at India Climate Dialogue

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