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CLIMATE CHANGE IS REWRITING OUR FUTURE: THE HIDDEN COSTS OF EXTREME HEAT
This past decade has been the hottest on record, and could have harmful repercussions for hundreds – if not thousands – of years
By Sigrid Vestergaard Frandsen, Director of Environmental Health
03/23/2026
According to the World Meteorological Organization (WMO), the Earth's climate is more out of balance than at any other time in observed history, as rapidly increasing greenhouse gas emissions continue to warm the atmosphere and oceans, as well as melt the polar ice caps.
The WMO 'State of the Global Climate' Report 2025 states that the past decade has been the warmest on record, with 2024 being the hottest year.
Earth's temperature changes in response to the rate at which energy from the sun enters and leaves the Earth's atmosphere. In 2024, increasing concentrations of greenhouse gases in the atmosphere (carbon dioxide, methane, and nitrous oxide) reached record levels not seen in over 800,000 years, and have reduced the rate at which energy leaves the Earth's climate system. This imbalance leads to an accumulation of excess energy on Earth, which we call "the climate crisis."
Annual global mean temperature anomalies relative to a pre-industrial (1850–1900) baseline. Source: WMO
One of the longest and most well-known records of climate change is that of the global mean near-surface temperature. Around 5% of the excess heat from climate change is warming the land, 1% is warming the atmosphere, and 3% is warming and melting the cryosphere. However, around 91% has been absorbed by the oceans, and ocean heat content reached a new record high in 2025.
These extreme weather changes have cascading impacts on our oceans, leading to biodiversity changes and losses, impacts on agricultural production, water scarcity, increasing displacement, and thawing of permafrost. These changes – caused by human activities – are increasingly disrupting the natural equilibrium and will have consequences for hundreds – if not thousands – of years to come, according to WMO Secretary-General Celeste Saulo. “On a day-to-day basis, our weather has become more extreme. In 2025, heatwaves, wildfires, drought, tropical cyclones, storms, and flooding caused thousands of deaths, impacted millions of people, and caused billions in economic losses,” said Celeste Saulo.
Climate change has wide-ranging impacts on mortality, livelihoods, ecosystems, and health systems and amplifies risks such as vector- and water-borne diseases and mental health stressors, especially among vulnerable populations. Dengue stands out as the world’s fastest-growing mosquito-borne disease, with about half the world's population at risk.
Extreme heat poses a fundamental threat to human health. It affects the physical environment as well as all aspects of both natural and human systems. It is a threat multiplier, undermining and reversing decades of health progress. As our climate changes, more frequent and intensifying heat events occur. These weather and climate hazards affect health both directly and indirectly, increasing the risk of deaths, noncommunicable diseases, the emergence and spread of infectious diseases, and health emergencies.
Now is the time for true, sustainable, and easily deployable solutions to the health crises brought on by increasing heat. Our Foundation is dedicated precisely to making those solutions available to vulnerable populations worldwide.