What is the issue?
Last week, Europe went through a heat wave that lasted for six days. It has smashed temperature records, left many people dead and caused huge fires to break out.
Why is it happening?
- The heat wave in Europe is a result of warm air masses from Africa, the World Meteorological Organization (WMO) said.
- It follows extreme heat episodes in India, Pakistan, parts of the Middle East and Australia.
- More events are expected to follow during this northern hemisphere summer.
What is a heat wave?
- Heat wave is a weather phenomenon which is a period of prolonged abnormally high surface temperatures relative to those normally expected.
- No standardized definition of a heat wave exists.
- WMO definition: If five or more consecutive days during which the daily maximum temperature surpasses the average maximum temperature by 5 °C or more, it is called heat wave.
- It may be characterized by low humidity (which may exacerbate drought) or high humidity.
How heat waves are classified?
- Classifying a heat wave varies from country to country.
- That is because what is seen as extremely hot in one place may seem within normal range in another.
- In 2016 – The WMO listed several factors to be considered while analysing an extreme weather event such as a heat wave.
- This includes defining a specific threshold for variables such as temperature to be considered extreme as well as a human perspective of extremes.
How heat waves are classified in India?
- The India Meteorological Department (IMD) classifies heat waves.
- It does not consider a heat wave unless the maximum temperature crosses 40°C and 30°C in the plains and hills respectively.
- Where the normal maximum is 40°C or less,
- Heat wave departure from normal – 5°C to 6°C
- Severe heat wave departure – 7°C or more.
- Where the normal maximum is more than 40°C,
- Heat wave departure from normal – 4°C to 5°C
- Severe heat wave departure – 6°C or more.
- In places where the maximum temperature reaches 45°C or more, the IMD declares a heat wave irrespective of the normal.
What is the controversy?
- Some scientists – Blamed climate change for these trends.
- WMO – It is too early for such an attribution.
- However, the WMO agreed that the heat wave is consistent with climate scenarios which predict more frequent.
- The WMO says that the drawn out and intense heat events as greenhouse gas concentrations lead to a rise in global temperatures.
What are its health hazards?
- It poses a risk to people’s health, agriculture and the environment.
- Babies and older people are particularly vulnerable as their bodies are not as well able to regulate their own temperatures.
- It can cause exhaustion and heat stroke.
- It can cause organ failure and breathing problems.
- The people living in urban areas are trapped in heat islands as steel, concrete, and asphalt structures absorb heat.
- In regions like Europe where people are not used to extremely high temperatures, many buildings don’t have air-conditioning.
Source: The Indian Express
