Photo CreditNASA

The habitual suspect in the three-decade-old trillion-dollar climate heist is, of course, human caused carbon dioxide (CO₂) emissions. But whether or not the temperature rise we’ve experienced is human caused, it could be that the self-proclaimed detectives in the media and public are being misled. CO₂, while having some impact on temperatures as all greenhouse gases do, is apparently like a petty thief stealing from a convenience store while a master thief makes away with millions from the bank. So, the question is: who is the real culprit?

A recent paper, published on July 5, 2025 in the journal Atmospheric Measurement Techniques, “Development and comparison of empirical models for all-sky downward longwave radiation estimation at the ocean surface using long-term observations,” was written mostly by Chinese researchers Peng, J. Jiang, B., et al. The researchers analysed over 30 years’ worth of radiation data (1998 – 2019) from 65 buoys on the ocean surface. Figure 1 shows the distribution of buoys from which measurements were taken. They discovered that cloud properties rather than CO₂ turn out to be the dominant factor in controlling surface longwave radiation, which is the energy that warms the ocean’s surface.

Figure 1: The distribution of buoys to measure ocean surface temperature (https://amt.copernicus.org/articles/18/2877/2025/)

The ocean surface is a key feature to study to understand the air-sea interactions. These interactions, in turn, are crucial in understanding the Earth’s climate. On his post on X.com, Earth scientist Dr. Matthew Wielicki explains: “Downward longwave radiation is the key mechanism by which the atmosphere transfers heat to the surface. If CO₂ were truly the primary driver of surface warming, you would expect changes in CO₂ to show up clearly.” However, that wasn’t found in the Chinese study.

Instead, the culprits were near-surface air temperature, humidity, cloud fraction, cloud liquid water, and cloud ice water. The Chinese researchers found that clouds turn out to be the master thief, and CO₂ doesn’t even make a dent in the factors affecting ocean temperature. Dr. Wielicki further explains that the authors of the study found that “explicitly accounting for cloud thermodynamics dramatically improves agreement with observations.” Clouds by far make up the dominant effect on ocean surface temperature. Although CO₂ does have some effect, the researchers found that it is not significant enough to be included in their models. 

The variables that were included in the study can be seen in Figure 2 below. Measurements of the downward longwave radiation were taken at each buoy with an infrared radiometer. The researchers state that “in total, 47,266 samples at the daily scale and 1,275,308 samples at the hourly scale during the period from 1988 to 2019 were used in this study.” Thus, they had a significant amount of data from which to develop their model.

Figure 2: Variables used in the study’s data analysis

(https://amt.copernicus.org/articles/18/2877/2025/)

Clouds are complicated. They are also highly variable—compare the cloud cover from day to day and you will see massive changes in the extent and types of clouds. They are also nonlinear, which means that they have an unpredictable sensitivity to initial conditions and complicated feedback loops. Small changes in the input of the climate system can lead to extremely large effects, and the reverse is also true. This is also called chaos, which, although not entirely random, is extremely hard to predict with sufficient accuracy. This also means that claims that we can control the global temperature by simply reducing CO₂ are grossly unfounded: there are so many factors at play with CO₂ only one small part of the picture. 

With regards to why models to track surface warming trends have failed in the past, Dr. Wielicki says that “The models aren’t wrong because physics is wrong... they’re wrong because clouds are doing the heavy lifting, and we still don’t understand them well enough to parameterize them without tuning.”

Image - https://commons.wikimedia.org/wiki/File:Sunset_wide_angle_with_clouds_Wokshots.jpg

Science-based Strategic Consultancy Luis G López Lemus also commented on the study, writing “While [t]his paper doesn’t shout, doesn’t challenge policy, nor doesn’t wave ideological flags, it actually points out that CO₂ may matter but clouds run the system where it counts, at the surface.”  Indeed, the work of real climate scientists is rarely loud and political but is key to understanding our ever-changing climate. While we can and should use findings such as these to help determine rational policy, they often get buried in the noise of activists and the media focusing on climate doom.

While developing a new model to study the radiation data, the researchers, Peng, J. Jiang, B., et al, found that “the accuracy of the newly constructed model is superior to that of other models” and that it has the potential to be more widely used in climate science. This approach to science—refining and testing models and comparing their accuracy with existing models and real-world data—is a key element of the scientific process that should not be overlooked. If we simply do what has been done before without refinement, we could be stuck with outdated systems that don’t accurately represent the real world. A key part of science is questioning, and if we didn’t question existing theories, we would still be thinking that the Earth was the centre of the universe and that it was impossible to break the atom into constituent parts. Although the science and data analysis in the paper is complex, it is also a simple measure of reality rather than clouded with politics and dogma.

We need to be more rigorous in climate science, a multifaceted and complex field that includes not only terrestrial affects from winds, clouds, volcanoes, and other factors, but influences from the Sun and outer space. We don’t understand the full picture of what shapes the Earth’s climate, but the suspects are becoming clearer, and CO₂ doesn’t look like the master thief anymore. So, trillions of dollars are being wasted every year across the world prosecuting what appears to be a minor criminal from a climate perspective, one that hugely benefits the natural and human world in other ways. The real temperature culprits, clouds, strike in a chaotic manner, and although their actions are largely unpredictable, this study helps us further our understanding of their dynamic influence on our planet’s climate. 

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Tom Harris is Executive Director of the International Climate Science Coalition - Canada. Mary-Jean Harris, BSc, MSc Physics, contributed to this article.