Topic: Heatwave and its global impact


What is a Heatwave? 

Globally, a heatwave is  considered to be an extended period of hot weather relative to the expected conditions of the area at that time of year, which may be accompanied by high humidity. While according to the World Meteorological Organisation, a heat wave is said to be a period of five or more consecutive days during which the daily maximum temperature exceeds the average maximum temperature by five degrees Celsius.

In India, a heatwave is considered when the maximum temperature at a grid point is 3?C or more than the normal temperature, consecutively for 3 days or more. Indian MEtereological Department of India provides following range and validity of time forecast:

Causes of heatwave

  • Heatwave can occur when a system of high atmospheric pressure moves into an area. The longer the system stays in an area, the hotter the area becomes. 
  • The main reason behind the heatwave in Western Europe is an abnormal high-pressure weather system sitting over Europe. It is because Europe is currently under a historically strong upper ridge (vast area that is affected by high-pressure air, which has trapped warm air in place.).
  • As a result, warm winds blowing northward from the Mediterranean and North African Sahara are getting forced Earthward by the high-pressure air and held in place.
  • Usually the warm air rises into the atmosphere and moves horizontally after reaching a particular hiehgt but the air in a high-pressure system is dense, so it pushes less dense air down, preventing the usual mixing. 
  • In this absence of mixing, the air on the ground just gets hotter leading to a further rise in temperature. It results in persistent dry and settled weather.
  • Such systems are also known as anti-cyclones because of the downward spiral of air opposite a cyclonic circulation in which the air moves in a generally upward direction.

  • When anticyclones are in place they do not allow the regular weather systems to progress. So, the formation of localised low-pressure systems or convections which can bring down the heat become less likely.

  • Thus, high pressure prevents the formation of clouds and thus rainfall and so heatwave type conditions are more likely in the summer months.


Source: Photo: U. S. National Weather Service/Wikimedia Commons

Heat Wave and Global Warming

There has not been any scientific confirmation of the link between heat wave and global warming.. A 2016 report from the National Academy of Sciences linked extreme heat in general to climate change. One study has suggested that climate change made European heat wave of 2003 twice as likely. 

According to a research paper published in the Current Climate Change Reports, one of the possible reasons for such a disruption is global warming especially in the Arctic region which disrupts the major jet stream over Earth’s North Pole. If this system gets disturbed, it impacts all other jet streams in lower latitudes which then form high pressure systems.

Heatwave in Europe

According to a meteorlogist, there has never been a high pressure system over Eurpoe that matches the current one. According to France's national weather agency, the number of heat waves in the country has doubled in the past 34 years and is expected to double again by 2050. 16 years ago, in 2003 Western Europe experienced a similar trend in which 15000 people in France died due to the severe summer heat wave and the death toll rose to 70,000. UK also experienced heatwave in 2018. Currently, Western Europe is experiencing a severe heat wave. 


Harmful Effects of Heatwave:

  • It can cause lose of lives 
  • It has adverse effects on mental health
  • In can cause infrastructural damage
  • It can even trigger devastating wildfires
  • It leads to unusually High Levels of Electricity Consumption, leading to power outages



Heat wave is a condition of increased atmospheric temperature and as it is potent enough to cause damage to lives and livelihood, it is considered as a disaster. The increase in the frequency of the occurence of such incidences has bring into the light another ill-effect of the climate change and global warning. It re-asserts the need to take the challenges posed by the global warming seriously and enhance international collaboration to save precious lives.