Updated July 21, 2021 at 11:41 am
- What effect do clouds have on Earth’s climate?
- Researchers have investigated this question and are now reporting that cloud cover actually contributes to the warming of Earth’s atmosphere.
- Those responsible describe how clouds actually affect climate using three main processes.
Clouds increase global warming – This is the result of a study that combines satellite images of clouds from the years 2000 to 2019 with machine learning methods. In addition, the researchers calculated a 3.2 °C increase in average temperature if The concentration of carbon dioxide (CO2) in the atmosphere Twice that of the pre-industrial era.
It could be by the middle of the century if no drastic measures are taken, warn in the “Proceedings” of the US National Academy of Sciences (“PNAS”) Paulo Seppi and Peer Nowak of Imperial College London.
Clouds play an important role
“Clouds have long been recognized as a major source of uncertainty in Earth’s climate response to human impacts,” the researchers write. “They play an important role in modifying the global energy balance.”
On the one hand, clouds shield solar radiation from the Earth’s surface and largely reflect it into space. On the other hand, however, they also reflect thermal radiation from the ground, making the atmosphere hotter.
What clouds do in the overall equilibrium is important for the calculation of climate sensitivity. It expresses how the climate reacts to higher concentrations of greenhouse gases. In their calculations, Seppi and Nowak refer to a doubling of the CO2 concentration from pre-industrial 280 ppm (parts per million – particulates per million air particles) to 560 ppm. It is currently approaching 420 ppm.
“Cloud formation part of a massively coupled system”
The researchers used satellite measurements on cloud radiation and combined them with data on meteorological effects. In their model, they included five controlling factors for cloud formation: temperature at Earth’s surface, estimated thickness of the boundary layer in inverse weather conditions, relative humidity in the lower and upper atmosphere, and wind speed at medium altitudes.
“Our approach enables us to learn how the variability of cloud radiation depends on the spatial patterns of controlling factors – an important advance, as cloud formation is part of a massively coupled system,” the scientists write.
Researchers identify three main processes
As a result, researchers identify three main processes in which clouds affect climate as the average air temperature rises:
- Due to high cloud cover, the temperature increases.
- Less cloud cover in the tropics is also expected to increase temperatures.
- If the water in the clouds at higher latitudes – that is, toward the poles – is liquid rather than freezing, the clouds provide cooling due to their low light permeability.
Seppi and Nowak calculated an average value of 0.43 watts per square meter and per degree of higher temperatures that clouds contribute to global warming. If CO2 concentrations double, it is likely to increase global temperatures by an average of 3.2 °C.
A maximum temperature increase of two degrees Celsius would be possible – but scientists put the probability at less than 2.5 percent. (FF/DPA)
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