147 - Half the world faces extra month of extreme heat

And it is not for summer coming

Author

The Climate Mentor
June 2nd, 2025 • Estimated Reading Time: 5 minutes

The silent scorcher🔥

Imagine stepping outside and feeling as though you're walking into an oven.

For nearly 4 billion people—half of the global population—that sensation became a prolonged reality between May 2024 and May 2025. A comprehensive study by World Weather Attribution, Climate Central, and the Red Cross reveals that human-induced climate change added at least 30 extra days of extreme heat in 195 countries during this period.

While floods and cyclones often dominate headlines, heatwaves are the stealthiest killers, exacerbating health issues, crippling economies, and straining infrastructure.

World map showing the number of extreme heat days (days when maximum temperatures exceed 90% of local historic temperatures) between May 1, 2024, and May 1, 2025, attributed to climate change. Data sourced from ECMWF ERA5 and the Climate Shift Index (CSI). Darker regions indicate higher numbers of extreme heat days, with especially high concentrations in equatorial Africa, South America, and parts of Asia. Map produced May 6, 2025

Heat map of climate-driven extreme Heat Days (May 2024 - May 2025)

Heat by the numbers

The data is alarming:

  • In Aruba, residents endured 187 days of extreme heat—142 more than expected without climate change.

  • Puerto Rico experienced 161 extreme heat days, a stark increase from the 48 days projected in a climate-neutral scenario.

  • Globally, the number of extreme heat days has at least doubled in nearly every country compared to a world without climate change.

These prolonged heat periods have led to increased mortality rates, particularly among vulnerable populations such as the elderly and those with pre-existing health conditions. Moreover, the economic ramifications are staggering.

Graph showing the ratio of climate extremes (e.g., heatwaves, droughts, and heavy rainfall events) from 1880 to 2040. The y-axis represents the ratio of extremes, while the x-axis shows years. A red line shows historical data with significant fluctuations, a blue line shows the projected trend with uncertainty shaded in blue. A clear increase is visible after 1980, with a steep rise in the ratio of extremes projected beyond 2020. Source: Climate model projections

Projected increase in climate extremes over time (1880–2040)

In the United States alone, the combined effects of extreme heat in 2024 cost over $162 billion, nearly 1% of the nation's GDP.

The strain on energy systems is equally concerning.

As temperatures rise, the demand for cooling escalates, leading to increased energy consumption and potential grid failures.

This vicious cycle underscores the urgent need for sustainable energy solutions and infrastructure resilience.

Scatter plot showing the relationship between national income rank (x-axis) and income change from human-caused heat waves (y-axis) for various countries. Each dot represents a country. The graph highlights that lower-income countries, which contribute less to global CO2 emissions, suffer greater income losses from heat waves. Malawi, marked in red, shows one of the largest income losses, while the United States, marked in blue, shows less economic impact despite higher CO2 emissions. The trend line shows a positive slope, indicating that higher-income countries experience less negative economic impact from heat waves. Labels indicate that low-income countries account for 11% of CO2 emissions, while high-income countries account for 89%.

Disproportionate impact of human-caused heat waves on low-income countries

Turning up the heat on solutions

The pervasive nature of extreme heat necessitates a multifaceted response, blending policy, innovation, and investment.

Exchange-traded funds (ETFs) like the iShares Global Clean Energy ETF (ICLN), First Trust Global Wind Energy ETF (FAN), and Invesco Solar ETF (TAN) have shown resilience and potential in this evolving market.

Governments and businesses must prioritize the development of early warning systems, urban planning that incorporates green spaces, and policies that mitigate heat-related risks. Investing in these areas not only safeguards communities but also offers substantial economic returns.

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