by Daniel Brouse and Sidd Mukherjee
August 10, 2025
I've been researching evaporation for decades, but sometimes the most telling experiments happen in my own backyard. At the start of this pool season, rainfall far exceeded evaporation. Then, for the past two months, the balance flipped: with little rain and intense heat, the pool lost about 10 inches of water solely from evaporation. This small observation mirrors what's happening globally -- a shift toward higher net water loss as temperatures climb.
In 2003, we invented Solar Powered Climate Control: Energy Transfer Through Evaporation. The idea was simple: collect rainwater and drip it over the roof on hot days. As the water evaporated, it absorbed heat from the structure, removing massive amounts of energy from the building.
When water evaporates, it transitions from liquid to vapor, a phase change that requires a huge energy input. In our experiments, Sidd calculated:
"For every cubic foot of water that evaporated, it took 61,000 BTU with it."
The results were remarkable: my electric bill dropped by two-thirds. Back then, I saw evaporation as a potential climate solution. Now, I see how climate change itself is supercharging evaporation -- and in ways that can harm as much as help.
Evaporation is among the most powerful natural cooling mechanisms on Earth. The latent heat of evaporation, L, measures the energy required to transform water into vapor without changing its temperature:
L = 8,094 BTU per gallon
1 BTU = 1,055 Joules
1 calorie raises the temperature of 1 gram of water by 1°C
Levaporation = 536 calories/gram
This means that even small amounts of evaporating water move massive amounts of energy from the surface into the atmosphere -- energy that doesn't just disappear, but fuels storms and weather extremes.
Evaporation cools surfaces locally, but globally it adds more water vapor to the atmosphere. According to the Clausius-Clapeyron equation, for every 1°C increase in temperature, air can hold about 7% more water vapor. In regions of the U.S. that are experiencing +10°C seasonal anomalies, the atmosphere can now hold about 70% more water vapor than in the past.
This fuels several dangerous trends:
Stronger storms -- The extra moisture is energy for hurricanes, atmospheric rivers, and severe thunderstorms.
More intense rainfall -- Raindrops are becoming larger and faster, increasing their momentum (p = mv). Higher drop count per second boosts total impact force.
Flash flood severity -- With more raindrops falling at higher velocities, momentum and destructive power increase significantly.
Erosion & soil degradation -- Heavy rains strip away topsoil, reducing agricultural capacity.
The drag equation shows that force increases with the square of velocity and is proportional to fluid density. This means:
Doubling wind speed quadruples its force.
Water is ~800x denser than air, so water flow at the same speed exerts ~800x the force of wind.
As climate change drives higher wind and water speeds, the destructive potential grows exponentially. A modest increase in velocity can translate into catastrophic increases in force -- toppling trees, collapsing infrastructure, and scouring soil.
Warming oceans -- particularly in the tropics -- are releasing increasing amounts of water vapor into the atmosphere. Atmospheric rivers transport this moisture and energy inland, fueling more intense rainfall events.
Death by Corn Sweat
On land, rising temperatures are accelerating evaporation from both plants and soil. By 2025, "corn sweat" had even entered weather forecasts. The term describes the large volumes of water vapor released by corn through transpiration -- the process by which plants draw water from their roots, move it up through the stalk, and emit it from tiny pores (stomata) in their leaves.
A mature cornfield can release thousands of gallons of water per acre per day into the atmosphere during peak growing season. The effect is often large enough that meteorologists factor corn sweat into heat-index and humidity forecasts for agricultural regions such as Iowa, Illinois, and Nebraska.
That extra moisture can push local humidity into dangerous ranges for people. The greatest near-term health risk isn't heat alone but the combination of heat and humidity -- known as deadly humid heat or wet-bulb temperature. Wet-bulb measurements mimic the body's evaporative cooling; when humidity is too high, sweat cannot evaporate and the body loses its ability to cool. In areas where corn sweat adds substantial moisture to the air, places that historically had lower humidity can become hazardous during heatwaves.
Transpiration at these levels also signals stress for the crop. Elevated temperatures and increased water loss can deplete soil moisture, reduce yields, and produce economic losses across farming regions already strained by climate change. In short, "corn sweat" is not only a public-health concern but also a threat to agricultural productivity and food security.
But here's the climate "whiplash" problem:
More extreme rainfall events lead to floods, soil loss, and infrastructure collapse.
More extreme droughts follow because warmer air strips moisture from the ground faster, especially when relative humidity remains low despite higher absolute humidity.
As soil moisture evaporates away, ecosystems degrade. Once soil structure collapses, desertification can set in -- a feedback loop that is much harder to reverse than to prevent.
Measuring the water loss in my swimming pool is straightforward. Measuring the net evaporation of the Earth's soils, forests, and croplands is far more complex -- but the trend is clear. Net evaporation is rising. Precipitation is becoming more extreme but also less reliable. Soil degradation is accelerating.
What began as an experiment in using evaporation to mitigate heat now reveals a stark reality: climate change is pushing evaporation into a new role as a driver of instability.
* Our climate model -- which incorporates complex social-ecological feedback loops within a dynamic, non-linear system -- projects that global temperatures could rise by up to 9°C (16.2°F) within this century. This far exceeds earlier estimates of a 4°C rise over the next thousand years, signaling a dramatic acceleration of warming.
Health feedback loops, violent rain, and deadly humid heat are fueling an exponential rise in climate-related deaths. This lethal triad -- disease, extreme heat, and intense rainfall -- demonstrates that climate change is not a distant threat but a rapidly accelerating public health emergency. These stressors interact and amplify one another, creating a cascade of compounding impacts that demand urgent intervention.
What Can I Do?
There are numerous actions you can take to contribute to saving the planet. Each person bears the responsibility to minimize pollution, discontinue the use of fossil fuels, reduce consumption, and foster a culture of love and care. The Butterfly Effect illustrates that a small change in one area can lead to significant alterations in conditions anywhere on the globe. Hence, the frequently heard statement that a fluttering butterfly in China can cause a hurricane in the Atlantic. Be a butterfly and affect the world.
Soil Degradation and Desertification
The Rapid Acceleration of Soil Degradation and Desertification Part II
The Converging Collapse: AMOC, Jet Streams, and Deadly Wet-Bulb Temperatures
Climate Change and Deadly Humid Heat
Burning to Stay Cool: How Our Fight Against Heat Is Fueling Climate Collapse
Solar Powered Climate Control: Energy Transfer Through Evaporation
Understanding Urban Heat Islands: Causes, Data, and Climate Context
Ignite a Domino Effect: Albedo, Brown Carbon, AMOC, Permafrost, Amazon Rainforest Dieback, Sea Level Rise Pulses, Hydroclimate Whiplash, and Arctic Sea Ice