For people with maths, physics and chemistry (and biology) backgrounds non-linear processes are familiar. For people without this background they are often quite obscure.
I’ll give a simple example. It’s not based on reality but it seems like the easiest way to explain non-linear effects.
Here we go..
Half the world is snow-covered land and half the world is ocean. Snow reflects about half of sunlight and ocean reflects no sunlight (this is not accurate, the actual figure is something like 10%, but we’ll stick with 0% for simplicity).
We also have clouds in this world. Clouds reflect 100% of sunlight.
Half of the sky has cloud cover. In our mythical world the land has cloudy skies and the ocean has clear skies.
So the cloud over the land reflects 100% of solar radiation while the ocean, with clear skies, absorbs all of its radiation.
Result – the mythical world absorbs 50% of solar radiation and so reaches some steady state temperature.
Now some climate change takes place. The winds are stronger and all the clouds move over the ocean. So the ocean has cloudy skies and the land has clear skies. Now the land reflects 50% of its sunlight (because of the snow) and the ocean region – because it’s covered by clouds – reflects 100% of sunlight.
Result – under the changed climate, the mythical world absorbs only 25% of solar radiation and cools dramatically
The important point is that clouds still cover 50% of the skies, and the ocean and land haven’t changed. But simply moving the clouds halves the sunlight absorbed.
A more realistic example is given by in Clouds & Water Vapor – Part Five – Back of the envelope calcs from Pierrehumbert which looks at regions of low humidity and high humidity.
Articles in this Series
Opinions and Perspectives – 1 – The Consensus
Opinions and Perspectives – 2 – There is More than One Proposition in Climate Science
Opinions and Perspectives – 3 – How much CO2 will there be? And Activists in Disguise
Opinions and Perspectives – 3.5 – Follow up to “How much CO2 will there be?”
Opinions and Perspectives – 4 – Climate Models and Contrarian Myths
Opinions and Perspectives – 5 – Climate Models and Consensus Myths
Opinions and Perspectives – 6 – Climate Models, Consensus Myths and Fudge Factors
Opinions and Perspectives – 7 – Global Temperature Change from Doubling CO2
The Science of Doom 
[…] « Opinions and Perspectives – 8 – Pattern Effects Primer […]
Nice to see honesty adressed. Björn Stevens of the Hamburg Max Planck Institute for Meteorology has got out of the echochamber, and places the problem on cloud patterns.
From Der Spiegel: “Simulating natural processes in the computer is always particularly sensitive when small causes produce great effects. For no other factor in the climatic events, this is as true as for the clouds. If the fractional coverage of low-level clouds fell by only four percentage points, it would suddenly be two degrees warmer worldwide. The overall temperature effect, which was considered just acceptable in the Paris Agreement, is thus caused by four percentage points of clouds – no wonder that binding predictions are not easy to make.
In addition, the formation of clouds depends heavily on the local conditions. But even the most modern climate models, which indeed map the entire planet, are still blind to such small-scale processes.”
“The Hamburg Max Planck researcher has therefore turned to another type of cloud, the cumulonimbus. These are mighty thunderclouds, which at times, dark and threatening, rise higher than any mountain range to the edge of the stratosphere.
Although this type of cloud has a comparatively small influence on the average temperature of the earth, Stevens explains. Because they reflect about as much solar radiation into space as they hold on the other hand from the earth radiated heat. But cumulonimbus clouds are also an important climatic factor. Because these clouds transport energy. If their number or their distribution changes, this can contribute to the displacement of large weather systems or entire climatic zones.”
“We need a new strategy,” says Stevens. He sees himself as obliged to give better decision support to a society threatened by climate change. “We need new ideas,” says Tapio Schneider from Caltech in Pasadena, California.
“For more than 20 years he has been researching in the field of climate modeling. It is not easy to convey this failure to the public. Stevens wants to be honest, he does not want to cover up any problems.”
https://judithcurry.com/2019/03/30/why-climate-predictions-are-so-difficult/#more-24846
There is no echo chamber. Clouds have been a recognized problem for as long as I have been reading about the subject: early 2000’s. Skeptics trying to dress up Bjorn Stevens as some sort of skeptic has gotten really hilarious. He is not a skeptic; he has more confidence in the prediction. The cloud scientists keep saying versions of this as they learn more about clouds: observation-based estimates of low climate sensitivity are likely biased low.
March anomaly is very high; you can bet low clouds are reflecting a lot less SW. That has been the case versus the hiatus since around 2013- 2014.
JCH. What is interesting is what B Stevens says or writes himself, not what someone disagreeing with you might mean.
And I also find it interesting that B Stevens has been so interested in “patterns”.
He is not differentiating himself from the pack. The pack is pattern effects. He leads the cloud pack. He wrote a paper in which he found a tiny “iris effect” when he fudged up the computer model, and suddenly the skeptics think he’s one of them.
I see that B Stevens is differentiating himself from “the pack”.
He sees it as a problem that IPCC has so great focus on using models to project the future, it is “the dead end science”. And scientists are adapting to this by try to find projects to satisfy this perspective. “The superstructure of trusting models”. It restrict scientific creativity and inquiery. Science is to create ideas and hypothesis and bring knowledge foreward. “Seeing the world as different from the way you ever saw it before.” I don`t think Judith Curry, or some other “sceptics”, would have said it very different.
https://forecastpod.org/2018/12/19/episode-4-bjorn-stevens/
Reblogged this on Climate- Science.press.