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The Criteria for Heatwaves, How Climate Change Is Affecting It

Heatwaves have become a significant concern in India, particularly in the eastern and southern regions. The increasing frequency and intensity of these heatwaves have been linked to climate change, raising alarm bells for policymakers, researchers, and citizens alike.


This blog delves into the science behind heatwaves, their implications, and the measures being taken to mitigate their impact.

What is a Heatwave?

A heatwave is characterized by excessively high temperatures compared to the usual climate patterns of a region. It is not merely the high temperature that defines a heatwave but the deviation from the normal temperature.

Attribution to Climate Change

Recent studies by the World Weather Attribution group have highlighted that the extreme heat in parts of India this April was made 45 times more likely due to climate change. This follows a pattern observed over the last three years, where early summer heatwaves in India have been attributed to global warming.

Key Findings:

  • 2022 and 2023 Heatwaves: Similar studies linked the excessive heat in March-April 2022 and April 2023 to climate change.
  • New Methodologies: Attribution science has developed tools to measure the likelihood of weather events being influenced by climate change.

Historical Data and Recent Trends

Heatwaves are common in northern, central, and eastern India during summer. However, the frequency, duration, and intensity of these heatwaves are increasing due to climate change.

Notable Instances:

  • February 2023: Parts of India experienced heatwave conditions, an anomaly as February is typically considered a winter month.
  • Odisha: Recorded an 18-day heatwave in April 2023, the second longest for the state.
  • Gangetic West Bengal: Experienced the highest number of heatwave days in April 2023 in the past 15 years.

Heatwave Criteria

Heatwaves are determined by deviations from normal temperatures rather than absolute high temperatures. For instance, a region accustomed to 27°C experiencing 35°C would be under a heatwave.

Health Risks

Prolonged exposure to high temperatures can lead to severe health issues, including dehydration, cardiovascular and respiratory diseases, and even death.

Statistics and Reporting:

  • Health Ministry vs. NCRB: In 2022, the Health Ministry reported 33 heat-related deaths, whereas the NCRB reported 730.
  • Data Collection: Efforts to improve data collection on heat-related illnesses and deaths began only a decade ago, leading to discrepancies in reported figures.

Economic and Social Impact

Heatwaves disrupt daily life and economic activities, particularly affecting outdoor labor sectors like agriculture and construction. School schedules and office timings often need adjustment to protect public health.

Heat Action Plans

All 23 states prone to heatwaves have implemented heat action plans to mitigate the effects. These include providing cool drinking water, distributing oral rehydration solutions, and regulating outdoor activities during peak heat hours.

Additional Measures

More comprehensive measures are necessary as heatwaves become more severe. This includes mandatory regulation of outdoor activities, adjusting work and school hours, and ensuring adequate funding for heat action plans.

StateNumber of Heatwave Days (April 2023)
Gangetic West BengalHighest in 15 years
Other StatesVaries
  • Heatwaves: Defined by abnormal high temperatures, increasingly linked to climate change.
  • Health Impact: Significant health risks, with inconsistent data on heat-related deaths.
  • Mitigation: Heat action plans in place, but more extensive measures needed for the future.

Q1. What is a heatwave?

A heatwave is defined by unusually high temperatures relative to the typical climate of a region.

Q2. How are heatwaves linked to climate change?

Studies have shown that climate change makes extreme heat events more likely and severe.

Q3. What are the health impacts of heatwaves?

Heatwaves can cause dehydration, cardiovascular and respiratory diseases, and increase the risk of sudden deaths.

Q4. What measures are being taken to mitigate heatwaves in India?

States have implemented heat action plans, including providing cool water, adjusting school and work hours, and distributing oral rehydration solutions.

Q5. Why is there a discrepancy in heat-related death reports?

Data collection on heat-related deaths has improved recently, but discrepancies remain due to varied reporting methods by different agencies.

By understanding the complexities and impacts of heatwaves in India, UPSC aspirants can better grasp the challenges posed by climate change and the importance of effective policy responses.

June 2024