The IPCC’s Moisture Miscalculation

Another ‘Settled Science’ Myth Crumbles

For decades, the Intergovernmental Panel on Climate Change (IPCC) and leading climate scientists have treated certain assumptions about Earth’s climate system as indisputable facts. One of the core tenets of modern climate science has been that as temperatures rise, the atmosphere’s ability to hold moisture increases, leading to more extreme weather events such as heavy rainfall, stronger storms, and prolonged droughts in other areas. This belief is baked into nearly every climate model and policy recommendation.

But what happens when one of these foundational assumptions turns out to be wrong? A new study, published in Geophysical Research Letters (2024), suggests that even basic understandings of how warming interacts with atmospheric moisture may need serious revision.

The Assumption: More Heat, More Moisture

One of the most cited principles in climate science is that warming increases the atmosphere’s capacity to hold water vapor, which then amplifies warming through the water vapor feedback loop. The Clausius-Clapeyron equation, a fundamental thermodynamic relationship, predicts that for every degree Celsius of warming, the atmosphere should hold about 7% more water vapor. This is the foundation for numerous climate projections predicting more intense storms and rainfall.

IPCC reports have consistently framed this as a certainty. The Sixth Assessment Report (AR6) asserts that “it is unequivocal that human influence has warmed the atmosphere, ocean, and land,” and that this warming is directly linked to “increases in atmospheric moisture.” This narrative has been used to justify climate policies aimed at reducing carbon emissions under the assumption that doing so will mitigate extreme weather, despite the fact that extreme weather events are not demonstrably increasing.

The Reality: Fundamental Flaws in Moisture Assumptions

The latest study in Geophysical Research Letters challenges this dogma by showing that the expected increase in atmospheric moisture has not occurred in key regions, or has followed patterns that contradict previous models. This means that the direct link between warming and increased atmospheric moisture is, at best, more complex than previously thought. At worst, it indicates that the models driving global climate policy are missing critical factors.