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Is Global Climate Change Making Heatwaves Worse?

global climate change
Heatwaves pose a direct threat to human health

Global climate change is causing a rise in average global temperatures. According to the Intergovernmental Panel on Climate Change (IPCC), the Earth’s average surface temperature has increased by about 1 degree Celsius since the late 19th century, with the last decade being the hottest on record. This warming trend is leading to more frequent and severe heatwaves.

These extreme weather events pose significant challenges to ecosystems, communities, and economies around the world. The IPCC report highlights that human activities, primarily the burning of fossil fuels, are the dominant cause of global warming. These activities release greenhouse gases like carbon dioxide, methane, and nitrous oxide into the atmosphere, trapping heat and driving temperatures upward.

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The Science Behind Heatwaves

Heatwaves are defined as extended periods of excessively high temperatures relative to a specific location’s average. The specific thresholds for a heatwave can vary depending on the region’s climate. However, they typically involve several consecutive days or weeks with temperatures exceeding the 90th percentile for the area.

Scientists have observed a clear link between global climate change and the increased frequency and intensity of heatwaves. Studies show that heatwaves are becoming more common due to several factors:

A warmer baseline

  • As the average global temperature rises, the baseline for what constitutes a “hot day” also increases. This means that heatwaves become more likely to occur even with relatively small temperature fluctuations.

Changes in atmospheric circulation patterns

  • Global warming can alter atmospheric circulation patterns, leading to stagnant air masses and persistently hot weather conditions over specific regions.

Reduced moisture availability

  • Heatwaves often coincide with droughts, as rising temperatures increase evaporation rates. This creates a feedback loop, as drier conditions allow the land surface to heat up more easily, further intensifying the heatwave.

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Global Climate Change and Heatwaves: Real-World Examples with Data

The devastating impact of heatwaves linked to global climate change is being felt around the world. Here are just a few examples from the last decade, with specific data on temperature increases:


A deadly heatwave swept across India in 2015, with temperatures in some regions exceeding 50°C (122°F). This event claimed thousands of lives and disrupted agriculture due to high temperatures and drought.


Extreme heat events in Australia have become more frequent and intense. In 2019, Australia experienced its hottest year on record, with the national average temperature exceeding 30°C (86°F) for the first time. These scorching conditions fueled devastating wildfires, bleached coral reefs on the Great Barrier Reef, and stressed ecosystems.


Pakistan has grappled with deadly heatwaves, particularly in urban areas like Karachi. In 2017, Karachi experienced a heatwave with peak temperatures reaching 49°C (119°F). Lack of infrastructure and preparedness worsened the effects on vulnerable populations, especially those living in densely populated areas with limited access to air conditioning.

United States

Heatwaves are becoming more common in the U.S., impacting cities like Phoenix, Arizona, and Las Vegas, Nevada. Phoenix has seen a significant increase in the number of days exceeding 40°C (104°F) in recent decades. These events strain energy grids and endanger public health, as many succumb to heatstroke and other heat-related illnesses.

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The Cascading Impacts of Heatwaves

The consequences of heatwaves are far-reaching and can be felt across various sectors:

Human health

Heatwaves pose a direct threat to human health, particularly for vulnerable populations like the elderly, children, and those with pre-existing health conditions. Heat stress can lead to a variety of health problems, including heat exhaustion, heatstroke, dehydration, and even death.


Extreme temperatures can devastate crops, reducing yields and increasing susceptibility to pests and diseases. Heat stress can stunt plant growth, disrupt pollination processes, and reduce crop quality. Rising temperatures can also lead to more frequent droughts, further impacting agricultural productivity.

Energy demand

During heatwaves, demand for air conditioning and cooling systems skyrockets. This can strain power grids, leading to blackouts and disruptions in essential services. The increased reliance on air conditioning during heatwaves also creates a feedback loop, as power plants often rely on fossil fuels for generation, further contributing to greenhouse gas emissions and global warming.

Water resources

Heatwaves can exacerbate water scarcity. Increased evaporation rates due to high temperatures can deplete water resources in rivers, lakes, and reservoirs. Additionally, the increased demand for water for irrigation during droughts puts further strain on water supplies.


Heatwaves can disrupt delicate ecological balances. Rising temperatures can harm wildlife populations, damage coral reefs, and alter migration patterns. Extreme heat events can also increase the risk of wildfires, which can have a devastating impact on ecosystems and biodiversity.

Written by Dr. Evelyn Karen

Dr. Evelyn Karen is a highly regarded Internal Medicine Physician with over 20 years of experience in Manila. Dr. Karen is passionate about patient well-being and champions innovative practices, including integrative medicine, telemedicine, and community outreach.

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