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I
Heatwaves: A brief note on the phenomenon
In recent weeks, the world has witnessed record-breaking temperatures from the US to Siberia. On 29 June, in British Columbia, the temperature touched 50 degrees Celsius, setting the national record for the highest-ever temperature in Canada. On 28 June, in the US, Portland recorded an all-time high temperature of 46.6 degrees Celsius, breaking the previous record set in 1965. On 4 July, in Europe, Finland recorded 33.5 degrees Celsius, which was its highest recorded temperature since 1914. On 24 June, Siberia recorded 48 degrees Celsius, which was its highest record. The record-breaking temperatures resulted in a prolonged heatwave which was attributed to the formation of a heat dome. The average death numbers increased unusually and evacuation orders were issued. Siberia, Canada, and the US are witnessing high temperatures consecutively for years.
A heatwave can be defined as a prolonged period of excessively hot weather that is above the normal average temperatures. World Meteorological Organization (WMO) defines a heatwave as a phenomenon when the daily maximum temperature is higher than the average maximum temperature by at least 5 degrees Celsius for five or more consecutive days. However, some countries have devised their own mechanisms to define heatwave based on the regional temperature gradients. Heatwaves can occur on land, ocean, and polar regions.
Marine heatwaves (MHW) are those which occur when ocean temperature is exceedingly warm for a prolonged period of time. According to Marine Heatwaves International Working Group, "a marine heatwave occurs when the seawater temperatures exceed a seasonally varying threshold (usually the 90th percentile) for at least five consecutive days. Successive heatwaves with gaps of two days or less are considered part of the same event."
While there are many factors causing marine heatwaves, ongoing studies show that a great amount of the heat from the atmosphere has gone into the oceans, implying that extremities in temperature can lead to warmer oceans. Currently, there is some evidence on the increasing frequency and intensity of the marine heatwaves.
The impact of the MHW is substantial on the marine ecosystem and the food chain of the oceans. An impact on the growth of zooplankton due to warming oceans, will in turn, impact the health, nutrition, and growth of fish, marine mammals that feed on them. In 2011, the excessive heat resulted in fish being washed ashore on the western coast of Australia, prompting the scientific community to understand the effects of MHWs on marine life.
Heatwaves in the polar regions serve as a climate alarm. Due to the high vulnerability factor, the polar regions are warming up at a higher rate than the global average rate. They are warming up about three times the average global rate. Consequently, there is a loss of ice sheets, permafrost, and wildlife. Glacier melt can result in rising sea levels, the formation of glacial lakes, and an increased risk of flash floods. However, the adverse impact of heatwave on the polar region will have global effects.
The Heat dome effect
According to the National Oceanic Administration of the US department of state, a heat dome occurs when the atmosphere traps hot ocean air like a lid or cap. The phenomenon begins when there is an increase in the temperature of the ocean. When the ocean warms up due to the sun's rays for a longer period of time, hot water rises up, and cold water settles down due to convection. The rising hot water starts escaping from the ocean. The high pressure above the ocean acts as a lid. The hot air tries to escape the lid formed by the high pressure; simultaneously, the jet streams flowing from the west to east further push the hot air back towards the ocean, and as a result, the air sinks and get hotter resulting in the formation of heat dome. In the case of the US and Canada, the Pacific Ocean has played a significant role in the formation of heat dome. Prolonged heating of the Pacific Ocean resulted in the formation of the heat dome.
In 2020, Death Valley, California, recorded a temperature of 54 degrees Celsius. Formation of heat dome is a usual phenomenon in the valley due to the complex geographic conditions; however, the formation of heat dome in populated regions such as the British Columbia and Oregon serve as climate alarm. ("Marine heatwaves explained", Marine Heatwaves International Working Group, updated in January 2021), (Eric Oliver, Markus Donat, Michael Burrows, et.al, "Longer and more frequent marine heatwaves over the past century", 10 April 2018), ("So, what are marine heatwaves?", NOAA, 8 October 2019), ("Fevers are plaguing the oceans- climate change is making them worse", Nature, 5 May 2021), (Jason Samenow, "The Northern Hemisphere has a punishing heat wave infestation", The Washington Post, 20 July 2021),(Mohammed Haddad, "Mapping the hottest temperatures around the world", Al Jazeera, 1 July 2021), ("What is a heat dome?", National Oceanic and Atmospheric Administration),(Matt Craig and Sophie Kasakove, "Death Valley Hits 130 Degrees as Heat Wave Sweeps the West", The New York Times, 10 July 2021)
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Heatwaves: A backgrounder
Strongest recorded heatwaves
The following section looks into the strongest heatwaves in terms of various factors, including temperature, impact, casualties, and duration. However, they are among the recorded heatwaves, and history is a witness to many more deadly heatwaves in the Global South that have not been reported.
The North American heatwave of 1936 resulted in record-breaking temperatures in almost 12 states of the US, and Ontario, and Manitoba in Canada. Few areas recorded more than 48.8 degrees Celsius mark, killing at least 5,000 Americans and 1,100 Canadians. The summer followed an extremely cold winter, leaving the population vulnerable to an extreme change in weather patterns. This heatwave, coupled with the Great Depression and imposed a heavy toll in economic and social terms.
The European heatwave of 2003 is one of the worst recorded heatwaves yet. July-August 2003 was termed as the hottest summer the continent witnessed since 1500 AD. The major cause for the extremely prolonged heatwave was attributed to the anti-cyclone over the western parts of Europe. The wave claimed the lives of at least 40,000 people across the continent, with France being the worst-hit country reporting 14,000 deaths.
India-Pakistan heatwave of 2015 between April to June claimed more than 2,500 lives in India and more than 1,100 lives in Pakistan. Most numbers of fatalities in India occurred in Andhra Pradesh and Telangana. South Asia, located in the tropical zone of the planet, is known for enduring extreme temperatures in summer. However, the intensity of the heatwaves is increasing every year in direct proportion to the changing climate.
Heatwaves in Australia, in terms of intensity, are now on an increasing trend. The worst of heatwaves have been experienced in the past decade, and scientists attribute it to human-induced climate change. The direct result of the extreme heat is the bush fire that proves disastrous to the unique flora and fauna of the country. The time period from 2019-20 saw one of the most devastating wildfire seasons, with hundreds of such incidents in New South Wales, Victoria and Queensland.
Extreme summers in parts of Africa are not an unknown fact. Sub-Saharan Africa has been termed as one of the hotspots for heatwaves. Yet, these incidents do not find a record in global databases such as the Emergency Events Database (EM-DAT) by the Centre for Research on the Epidemiology of Disasters, Belgium. EM-DAT has listed only two heatwaves in sub-Saharan Africa in the 20th century and 70 related deaths. However, in the same time frame, more than 80 heatwaves and 140,000 deaths were recorded in Europe.
Geographical distribution of heatwaves
The phenomenon of a heatwave is on an escalation ladder since the 1950s, with the biggest increases in parts of Africa, the Middle East, and South America. Perkins-Kirkpatrick and Lewis (2020) used the concept known as 'cumulative heat' and assessed that heat produced in parts of Africa is increasing by 10 degrees Celsius. 'Cumulative heat' considers the excess heat or the temperature anomaly recorded above the average air temperature that indicates a heatwave. Studies show that southern, east, and northern Africa are under increased heatwave duration and intensity. A similar situation exists in parts of South America and the Middle East, where excess heat produced, is increasing by 10 degrees Celsius each decade.
Heatwaves in Europe are reportedly increasing since the 1970s and more evident since 2003. Along with factors such as North Atlantic Oscillation, El Nino, and warming of the North Atlantic Ocean, anthropogenic activity-induced climate change and rapidly changing Arctic weather patterns are the primary causes for amplifying heat in the European continent.
Climate Change and Anthropocene Epoch
In the past decades, extreme weather events are occurring frequently. The increase in the frequency, intensity, and duration of such events can be attributed to anthropogenic climate change. After 1950, extreme weather events such as droughts, storms, and floods have unusually increased. The rise in global temperatures has further accelerated the occurrence of extreme weather events. According to the Fifth Assessment Report by the Intergovernmental Panel on Climate Change, the extreme weather events will increase as the global temperature rises. Globally and regionally, there is an increase in the frequency, intensity, and duration of heatwaves.
According to scientists, a new epoch known as the Anthropocene epoch should be declared because the impact of human activity on the earth is profound. The current epoch, the Holocene, a period of stable climate since the last ice age, must come to an end. After 1950, human activity has dominated the earth's system. The rise in greenhouse gas emissions, rise in the sea level, melting of glaciers, deforestation has impacted the earth's climate in irreversible ways. However, the epoch is not yet officially recognized. The proposal of a new epoch highlights the irreversible damage human activity has done to the planet's ecosystem. The rise in the frequency, intensity, and duration of extreme weather events like heatwaves is one of the manifestations of anthropogenic climate change. ("Heat Waves Throughout History", History, 27 July 2020), ("Why Africa's heatwaves are a forgotten impact of climate change", Carbon Brief, 13 July 2020), ("Climate Concern: Extreme Heatwaves are not being recorded in sub-Saharan Africa", University of Oxford, 13 July 2020), ("India heat wave kills thousands", NOAA, 9 June 2015), ("European heat wave of 2003", Britannica, 2003), ("Australia suffers worst heatwave in century", Gulf News, 29 January 2009), (Eric Oliver, Markus Donat, Michael Burrows, et.al, "Longer and more frequent marine heatwaves over the past century", Nature Communications, 10 April 2018), (SE Perkins- Kirkpatrik and SC Lewis, "Increasing trends in regional heatwaves", 3 July 2020), ("An overview of the intensity and frequency of extreme weather events", Green Peace), (Ruonan Zhang, Chenghu Sun, Jieshun Zhu, et.al, "Increased European heat waves in recent decades in response to shrinking Arctic sea ice and Eurasian snow cover", 18 February 2020), ("The Anthropocene epoch: scientists declare dawn of human-influenced age," The Guardian, 29 August 2016)
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Fallouts of the Heatwaves: Health, Economy and Environment
The impact of extreme heat on human health depends on various parameters including adaptation, preparedness, health policy, age, socio-economic conditions, and the amount of heat. Heatwaves can increase morbidity and mortality rates. According to the World Meteorological Organization, the number of fatalities due to extreme heat increased 2300 per cent between 1991-2010 making heatwave the most dangerous climate disaster. According to the World Health Organization, more than 1,66,000 people died due to heat waves from 1998-2017. The impact of extreme heat was found to be more on the older population. The immediate health impacts include dehydration, heatstroke, heat rash, increase in body temperatures, and heart rate. Other health impacts include organ, cardiological, cerebral and respiratory diseases.
Heatwaves can result in huge economic losses. Apart from human and wildlife loss, heatwaves can induce increased health costs and infrastructural damage. In 2020, the US spent USD 95 billion on climate-related disasters. Additionally, the agricultural losses, reduction in agricultural exports, increase demand for electricity also incurs huge costs. Extreme heat also results in a reduction in work productivity. Globally, two per cent of the total working hours are lost due to high heat.
Extreme heat can adversely affect crop yield. High temperature can increase stress levels in plants, decreased photosynthesis, pollen production, and seed absorption. This results in a decrease in grain number and weight. Reduction in food production can result in higher food prices leading to lesser access to food. In 2018, European heatwaves led to the widespread failure of harvest across the continent.
Heatwaves can have an impact on energy production. It can cause disruption in power generation and supply due to the high demand for power. Consequently, the high demand can result in power blackouts. Moreover, the transmission lines get damaged and there is an expansion in resistance of the lines. Extreme heat can affect the capacity of nuclear plants, renewables, and fossil fuels. The water bodies near the power plants get heated up, which can result in dressed heat absorption from the power plants resulting in energy inefficiency.
Heatwaves can lead to increased leaf fall resulting in the conversion of carbon sinks into carbon sources. It can result in an unusual increase in precipitation levels in the arid regions. Additionally, extreme heat can lead to the melting of the glaciers and permafrost, which can accelerate the formation of lakes leading to an increase in the possibility of flash floods and glacial lake outbursts. Moreover, it can increase the possibility of sparking wildfires and the urban heat island effect. Extreme heat can prove to be fatal for wildlife and aquatic species.
Finally, heatwaves have more impact on vulnerable populations. The elderly population, economically poor, women, children are adversely affected by extreme heat. Furthermore, the impact has been seen more in lower and middle-income countries than the high-income countries due to variability in the living conditions and distribution of resources. (Sharon Campbell et al., "Heatwave and health impact research: A global review", Health & place, 2018), (TordKjellstrom et al., "Working on a warmer planet: The effect of heat stress on productivity and decent work",International Labour Organization, 2019),(Steve Miller et al, "Heat Waves, Climate Change, and Economic Output", Journal of the European Economic Association, 2021),(World Meteorological Organization, "The Global Climate 2001-2010. A Decade of Climate Extremes", 2013), ("Extreme Weather and Climate Change", Centre for Climate and Energy Solutions)
IV
Addressing the heatwaves: Common issues, different strategies
The US, Canada, and parts of European countries are reeling under severe heatwave conditions, prompting emergency measures by the authorities.
In Canadian small towns like Lytton, the heatwave has killed hundreds of people. Given the lack of fans or air conditioners at homes in towns, the government has opened cooling centers, to enable the residents and homeless, to take shelter. In order to limit traveling, educational institutions were ordered to be closed, and roads to be closed. Thousands of vulnerable people in terms of exposure to the heat and facilities were evacuated to safer places.
The United States has undertaken similar measures to manage the heat dome. On 29 June, President Biden said that the heatwave is related to climate change, and laid out a strategy to upgrade the country's infrastructure accordingly. Extreme temperatures have triggered major wildfires in the region, threatening flora and fauna. Nearly 50 instances of wildfires were recorded in Canada between 10-12 July. Both the countries have deployed firefighters on the ground and choppers pouring water to douse the fire.
Europe experienced the heatwave prior to the current floods that are severely affecting countries like Germany. Villages and towns were evacuated in Cyprus and Greece, with wildfires raging across Spain, Cyprus, Italy, Russia, and Greece. The Siberian wildfires, increasing each year in intensity and frequency, threatened the unique Arctic biodiversity. However, areas with a human population are under focus, rather than a widespread approach in dousing fires that are ravaging the Siberian landscape. The short-term strategy for tackling the current heatwave seems similar across countries. ("Heatwave: US firefighters struggle to contain wildfires while Canada announces new measures", Independent, 12 July 2021), ("US, Canada hit by new round of scorching hot temperatures", Hindustan Times, 12 July 2021), ("Hundreds believed dead in heatwave in Canada despite efforts to help", Business Standard, 2 July 2021)
Conclusion
Heatwaves are linked to the larger climate change issues that are being witnessed across the world in various forms. Acknowledging and reporting these events, particularly in South America and Africa, are the first steps towards effective management of heatwaves.
Due to the link to anthropogenic activities, it is of utmost necessity to sustain climate action at the national, regional, and at international levels. Specifically with regard to the heatwaves, implementation of long-term heatwave action plans with mitigation and adaptation strategies must be in place in key regions that heavily reel under the effects of heatwaves and occasional heat domes.
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