Simple equations clarify cloud climate conundrum, say researchers

Posted: April 2, 2024 by oldbrew in Clouds, modelling, research, Temperature, Uncertainty
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The paper, Weak anvil cloud area feedback suggested by physical and observational constraints, says in the section headed ‘Implications of uncertainty’: ‘A rigorous assessment of the anvil cloud area feedback was lacking because the confounding factors of cloud overlap and a changing cloud radiative effect on the feedback could not be accounted for.’ However, in the article at EurekAlert we find: ‘New analysis based on simple equations has reduced uncertainty about how clouds will affect future climate change’. A somewhat mixed picture there. The chicken/egg climate/clouds ‘conundrum’ remains.
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Clouds have two main effects on global temperature – cooling the planet by reflecting sunlight, and warming it by acting as insulation for Earth’s radiation.

The impact of clouds is the largest area of uncertainty in global warming predictions.

In the new study, researchers from the University of Exeter and the Laboratoire de Météorologie Dynamique in Paris created a model that predicts how changes in the surface area of anvil clouds (storm clouds common in the tropics) will affect global warming.

By testing their model against observations of how clouds impact warming in the present day, they confirmed its effectiveness and thereby reduced uncertainty in climate predictions. [Talkshop comment – an optimistic assessment?].

The model shows that changes in the area of anvil clouds have a much weaker impact on global warming than previously thought.

However, the brightness of clouds (determined by their thickness) remains understudied, and is therefore one of the largest obstacles to predicting future global warming.

“Climate change is complex, but sometimes we can answer key questions in a very simple way,” said lead author Brett McKim.

“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.

“That’s 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.” [Talkshop comment – or does the brightness of clouds affect warming?]

Full article here.
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Image: Anvil of a thundercloud over Columbia [credit: Eulenjäger @ Wikipedia]

Comments
  1. Ron Clutz says:

    The claim in the title exaggerates the significance of this narrowly scoped study. It only concerns anvil cloud, and only those in the tropics. It trys to constrain the uncertainty of radiative feedbacks from changes in the area of such clouds, setting aside the huge climate impact from the latent energy transfers involved. It admits that the much larger RF issue is not the cloud area, but the albedo (optical density) which is still guesswork.

    That being said, the topic is contemporary since Nobel Laureate Clauser was disinvited from speaking due to his skepticism over climate models due to their failures including clouds are key climate factors. Indeed CMIP6 versions run even hotter than CMIP5 owing to worse cloud parameters. I have a post that goes into this in some detail.

    https://rclutz.com/2023/07/23/how-climate-models-get-clouds-wrong/

  2. liardetg says:

    How I love that “threshold of 2 degrees set by the Paris Agreement”. I mean, how ‘set’? And upon what scientific basis? And who has done anything about it? And what change in the Keeling Curve has happened? And. What happens if it’s exceeded? Has it been already? No thermometers in the southern hemisphere in 1850. Fall about laughing. Wise old man Trump pulled the American taxpayer out.

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