New research using basic equations has decreased uncertainty about how clouds will influence future climate change.
Anvil clouds. Image number ISS042-E-215303 from the International Space Station. Image Credit: Earth Science and Remote Sensing Unit, NASA Johnson Space Center
Clouds have two primary effects on global temperature: they cool the planet by reflecting sunlight and warm it by providing radiation insulation.
The most significant source of uncertainty in estimates of global warming is the effect of clouds.
A model that forecasts how variations in the surface area of anvil clouds—storm clouds that are frequent in the tropics—will impact global warming was developed by researchers at the University of Exeter and the Laboratoire de Météorologie Dynamique in Paris in the new study.
They proved the efficiency of their model by evaluating it against observations of how clouds influence warming, reducing uncertainty in climate predictions.
The model demonstrates that variations in the area of anvil clouds have a substantially lower influence on global warming than previously believed.
However, the brightness of clouds (determined by their thickness) is still poorly understood, making it one of the most significant challenges to predicting future global warming.
Climate change is complex, but sometimes we can answer key questions in a very simple way. In this case, we simplified clouds into basic characteristics: either high or low, their size and the temperature. Doing this allowed us to write equations and create a model that could be tested against observed clouds. Our results more than halve uncertainty about the impact of the surface area of anvil clouds on warming.
Brett McKim, Study Lead Author and PhD Student, University of Exeter
McKim added, “That is a big step – potentially equivalent to several years’ difference in when we expect to reach thresholds such as the 2 °C limit set by the Paris Agreement. We now need to investigate how warming will affect the brightness of clouds. That’s the next stage of our research.”
A Fulbright scholarship funded McKim’s work at the Laboratoire de Météorologie Dynamique.
Journal Reference:
McKim, B., et. al. (2024) Weak anvil cloud area feedback suggested by physical and observational constraints. Nature Geoscience. doi:10.1038/s41561-024-01414-4