Cloud Loss Could Add 8 Degrees to Global Warming

[Eugene]

Source: Quanta Magazine

A World Without Clouds

A state-of-the-art supercomputer simulation indicates that a feedback loop between global warming and cloud loss can push Earth’s climate past a disastrous tipping point in as little as a century.

Natalie Wolchover
Senior Writer/Editor

February 25, 2019

-snip-

More data points surfaced in China, then Europe, then all over. A picture emerged of a brief, cataclysmic hot spell 56 million years ago, now known as the Paleocene-Eocene Thermal Maximum (PETM). After heat-trapping carbon leaked into the sky from an unknown source, the planet, which was already several degrees Celsius hotter than it is today, gained an additional 6 degrees. The ocean turned jacuzzi-hot near the equator and experienced mass extinctions worldwide. On land, primitive monkeys, horses and other early mammals marched northward, following vegetation to higher latitudes. The mammals also miniaturized over generations, as leaves became less nutritious in the carbonaceous air. Violent storms ravaged the planet; the geologic record indicates flash floods and protracted droughts. As Kennett put it, “Earth was triggered, and all hell broke loose.”

The PETM doesn’t only provide a past example of CO2-driven climate change; scientists say it also points to an unknown factor that has an outsize influence on Earth’s climate. When the planet got hot, it got really hot. Ancient warming episodes like the PETM were always far more extreme than theoretical models of the climate suggest they should have been. Even after accounting for differences in geography, ocean currents and vegetation during these past episodes, paleoclimatologists find that something big appears to be missing from their models — an X-factor whose wild swings leave no trace in the fossil record.

Evidence is mounting in favor of the answer that experts have long suspected but have only recently been capable of exploring in detail. “It’s quite clear at this point that the answer is clouds,” said Matt Huber, a paleoclimate modeler at Purdue University.

Clouds currently cover about two-thirds of the planet at any moment. But computer simulations of clouds have begun to suggest that as the Earth warms, clouds become scarcer. With fewer white surfaces reflecting sunlight back to space, the Earth gets even warmer, leading to more cloud loss. This feedback loop causes warming to spiral out of control.

-snip-

Read more: https://www.quantamagazine.org/cloud-loss-could-add-8-degrees-to-global-warming-20190225/

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Related: Possible climate transitions from breakup of stratocumulus decks under greenhouse warming (Nature Geoscience)

[matt819]

1. Regarding PETM

I'm a believer in climate change. Which is kind of like saying I believe in air. Or water. Or gravity. It's not something you believe it. It's something that *is*.

If I'm reading the info right about PETM - no guarantee, mind you - it seems that the earth went through major and highly adverse warming many millions of years ago when there were no humans doing stuff.

Yes, climate change now is due to human interference with, well, with everything. But to what degree (haha) is more or less natural warming at work. Maybe we're at the point where it would happen anyway.

Probably not. But the question explains why I'm not a scientist of any kind.

[OKIsItJustMe]

4. Today's rate of carbon emission build-up is much faster than the natural increase related to PETM

https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum#Comparison_with_today's_climate_change

…

Comparison with today's climate change

Model simulations of peak carbon addition to the ocean–atmosphere system during the PETM give a probable range of 0.3–1.7 Petagrams of Carbon per year (Pg C/yr), which is much slower than the currently observed rate of carbon emissions. It has been suggested that today's methane emission regime from the ocean floor is potentially similar to that during the PETM.

…

https://www.climate.gov/news-features/features/models-and-fossils-face-over-one-hottest-periods-earths-history

[NickB79]

5. Based on planetary wobble, we should be going back into an Ice Age by now

https://www.bloomberg.com/news/articles/2016-01-13/the-good-news-on-global-warming-we-ve-delayed-the-next-ice-age

So no, the warming we're seeing now is all on us.

[OKIsItJustMe]

2. High CO₂ Levels Can Destabilize Marine Layer Clouds

https://www.caltech.edu/about/news/high-cosub2sub-levels-can-destabilize-marine-layer-clouds

High CO₂ Levels Can Destabilize Marine Layer Clouds
February 25, 2019

At high enough atmospheric carbon dioxide (CO₂ ) concentrations, Earth could reach a tipping point where marine stratus clouds become unstable and disappear, triggering a spike in global warming, according to a new modeling study.

This event—which could raise surface temperatures by about 8 Kelvin (14 degrees Fahrenheit) globally—may occur at CO₂ concentrations above 1,200 parts per million (ppm), according to the study, which was published in Nature Geoscience on February 25. For reference, the current concentration is around 410 ppm and rising. If the world continues burning fossil fuels at the current rate, Earth's CO₂ level could rise above 1,200 ppm in the next century.

"I think and hope that technological changes will slow carbon emissions so that we do not actually reach such high CO₂ concentrations. But our results show that there are dangerous climate change thresholds that we had been unaware of," says Caltech's Tapio Schneider, Theodore Y. Wu Professor of Environmental Science and Engineering and senior research scientist at the Jet Propulsion Laboratory, which Caltech manages for NASA. Schneider, the lead author of the study, notes that the 1,200-ppm threshold is a rough estimate rather than a firm number.

The study could help solve a longstanding mystery in paleoclimatology. Geological records indicate that during the Eocene (around 50 million years ago), the Arctic was frost free and home to crocodiles. However, according to existing climate models, CO₂ levels would need to rise above 4,000 ppm to heat the planet enough for the Arctic to be that warm. This is more than twice as high as the likely CO₂ concentration during this time period. However, a warming spike caused by the loss of stratus cloud decks could explain the appearance of the Eocene's hothouse climate.

…

http://dx.doi.org/10.1038/s41561-019-0310-1

[OKIsItJustMe]

3. Earth could warm by 14C as growing emissions destroy crucial clouds

https://www.newscientist.com/article/2194781-earth-could-warm-by-14c-as-growing-emissions-destroy-crucial-clouds/

Earth could warm by 14°C as growing emissions destroy crucial clouds
25 February 2019

By Michael Le Page

If we keep burning fossil fuels with reckless abandon, we could trigger a cloud feedback effect that will add 8°C on top of all the warming up to that point. That means the world could warm by more than 14°C above the pre-industrial level.

Needless to say, this would be cataclysmic. For instance, large parts of the tropics would become too hot for warm-blooded animals, including us, to survive.

The good news is that if countries step up their efforts to cut emissions we should avoid finding out if this idea is correct. “I don’t think we will get anywhere close to it,” says Tapio Schneider at the California Institute of Technology, Pasadena, who led the research.

Schneider’s team modelled stratocumulus clouds over subtropical oceans, which cover around 7 per cent of Earth’s surface and cool the planet by reflecting the sun’s heat back into space. They found there was a sudden transition when CO2 levels reached around 1200 parts per million (ppm) — the stratocumulus clouds broke up and disappeared.

…

https://doi.org/10.1038/s41561-019-0310-1

[Judi Lynn]

6. Climate Change Could Make These Super-Common Clouds Extinct, Which Would Scorch the Planet

By Rafi Letzter, Staff Writer | February 25, 2019 03:12pm ET

- click for image -

https://img.purch.com/h/1400/aHR0cDovL3d3dy5saXZlc2NpZW5jZS5jb20vaW1hZ2VzL2kvMDAwLzEwNC80NzIvb3JpZ2luYWwvc2h1dHRlcnN0b2NrXzY3NDE3Nzk5OC5qcGc=

This is a picture of stratocumulus clouds.
Credit: Shutterstock

If humanity pumps enough carbon dioxide into the atmosphere, one of Earth's most important types of cloud could go extinct. And if the stratocumulus clouds — those puffy, low rolls of vapor that blanket much of the planet at any given moment — disappear, Earth's temperature could climb sharply and radically, to heights not predicted in current climate models.

That's the conclusion of a paper published today (Feb. 25) in the journal Nature Geoscience and described in detail by Natalie Wolchover for Quanta Magazine.

As Wolchover explained, clouds have long been one of the great uncertainties of climate models. Clouds are complicated, small and fast-changing. Computer models that easily capture the complexity and detail of most climate systems just aren't powerful enough to predict worldwide shifts in cloud behavior. [7 Ways the Earth Changes in the Blink of an Eye]

But clouds are important. They dye a wide swath of the atmosphere white, as seen from space, reflecting sunlight away from Earth's surface. And stratocumulus clouds are an important part of that picture; they're those white blankets you might have seen as you looked out the window of an airplane, rolling out below you and hiding the ground. Researchers suspect that certain sudden, past jumps in temperature may have been caused by changes to clouds like these.

More:
https://www.livescience.com/64852-clouds-extinct-climate-change.html

[femmedem]

7. WaPo has picked the story up as well.

https://www.washingtonpost.com/climate-environment/2019/02/25/very-high-carbon-dioxide-could-suppress-cooling-clouds-climate-change-model-warns/?utm_term=.e15e9a54c89f