Clouds feedback

The Clouds Feedback and the Clouds Tipping Point

The clouds feedback refers to disappearance of the lower clouds, more specifically the stratocumulus decks. Stratus cloud decks cover about 20% of subtropical oceans and are prevalent in the eastern portions of those oceans—for example, off the coasts of California or Peru. The clouds cool and shade Earth as they reflect the sunlight that hits them back into space. Tapio Schneider et al. calculated that these clouds begin to break up when CO₂e levels rise above the tipping point of 1,200 ppm.

Disappearance of these clouds will make the temperatures go up strongly and rather abruptly. By the time CO₂e levels will have risen to this clouds tipping point of 1,200 ppm CO₂e, temperatures will already have gone up a lot in line with the warming from rising CO₂e levels. On top of this, the clouds feedback itself triggers an additional surface warming of some 8°C globally.

Possible climate transitions from breakup of stratocumulus decks under greenhouse warming - by Tapio Schneider et al., published February 25, 2019.

Discussion at facebook starting February 26, 2019: 

Discussion in post at Arctic-News blog: 
When will we die?
discussed at facebook at:

News release:
High CO₂ Levels Can Destabilize Marine Layer Clouds, published February 25, 2019.

Clouds and the Climate Tipping Point - T. Schneider - April 24, 2019

Earth System Modeling 2.0: Toward Data-Informed Climate Models With Quantified Uncertainties - by Tapio Schneider | Earth System Modeling 2.0: Toward Data Informed Climate Models w/ Uncertainty - December 8, 2020

Possible climate transitions from breakup of stratocumulus decks under greenhouse warming

AI-Accelerated Climate Modeling | by Tapio Schneider

Specific questions answered in the study:

1. Is the tipping point 1200 ppm CO₂ or CO₂e?
CO₂ levels here should be understood as the equivalent CO₂ levels that correspond to a change in the concentration of all well-mixed greenhouse gases. When a CO₂ threshold is crossed at around 1,200 ppm, the stratocumulus decks abruptly become unstable and break up into scattered cumulus clouds. When the atmospheric concentration of greenhouse gases (for example, CO₂ and H₂O) increases (1,200 ppm), the longwave cooling of the cloud tops weakens, because the downwelling longwave radiation that reaches the cloud tops from above emanates at lower levels with higher temperatures relative to the cloud-top temperatures.

2. How difficult is it to reverse the clouds feedback once the tipping point has been crossed? 
When CO₂ levels are lowered again after the stratocumulus breakup, the stratocumulus decks only reform once the CO₂ levels drop below 300 ppm.

3. How is the 8°C temperature rise calculated?
Subtropical marine stratocumulus clouds cover about 6.5% of the Earth’s surface and, where they occur, reduce the solar radiative energy flux absorbed in the climate system by ~110 Wm⁻², compared to about a 10 Wm⁻² reduction by scattered cumulus. If we assume a climate sensitivity parameter of 1.2 K (Wm⁻²)⁻¹ (as for the more sensitive among current GCMs), this implies (110−10) Wm−2×6.5%×1.2 K (Wm⁻²)⁻¹ ≈8K global-mean surface warming when subtropical marine stratocumulus break up.

From selected posts

1. Abrupt stratocumulus cloud shattering

[ from earlier post ]
Catastrophic crack propagation is what makes a balloon pop. Could low-lying clouds similarly break up and vanish abruptly?

Could peak greenhouse gas concentrations in one spot break up droplets into water vapor, thus raising CO₂e and propagating break-up of more droplets, etc., to shatter entire clouds?

Moreover, could an extra burst of methane from the seafloor of the Arctic Ocean alone suffice to trigger the clouds tipping point and then abruptly push global temperatures up by an additional 8°C?

• Overshoot or Omnicide?

This possibility is explored further below. 

2. Potential rise by 2026

Below follows an an extract from the post:  

CO₂ concentration at Mauna Loa on December 9, 2021, was 415.78 ppm and on January 26, 2022, it was 420.52 ppm. The MetOp-B satellite recorded a global mean methane level of 1958 ppb on October 25, 2021 am at 295 mb, and when using a 1-year GWP of 200, this translates into 391.6 ppm CO₂e. Together with the above level of CO₂, that's 391.6 + 420.52 = 812.12 ppm CO₂e.

Now add an additional 5 Gt of methane from an abrupt eruption of the seafloor, which is only 10% of the 50 Gt that Natalia Shakhova et al. warned about long ago, while 50 Gt is in turn only a small fraction of all the methane contained in sediments in the Arctic. On its own, such an eruption of seafloor methane could raise the global mean methane concentration by almost 2000 ppb which, at a 1-year GWP of 200, would translate into 400 ppm CO₂.

So, that would abruptly cause the joint CO₂e of just two greenhouse gases, i.e. methane and CO₂, to cross the 1200 ppm clouds tipping point, triggering a further 8°C global temperature rise, due to the clouds feedback.

A 5 Gt seafloor methane burst would double the methane in the atmosphere and could instantly raise CO₂e level to above 1200 ppm, thus triggering the cloud feedback (panel top right). Even with far less methane, levels of further pollutants could rise and feedbacks could strengthen, while sulfate cooling could end, and a 18.44°C rise (from pre-industrial) could occur by 2026 (left panel). Meanwhile, humans will likely go extinct with a 3°C rise, and a 5°C rise will likely end most life on Earth.

Above image and caption are from the post: 

3. Rate of change

Important also is the rate of change. Current temperatures are rising faster than they ever did in history. 
[ from: When will humans go extinct? ]

From the post:
• When will humans go extinct?

Related studies

1. Earthshine decline

• News release: Earth is dimming due to climate change
Warming oceans cause fewer bright clouds to reflect sunlight into space, admitting even more energy into earth's climate system

• Study: Earth's Albedo 1998–2017 as Measured From Earthshine - by Philip Goode et al.

discussed at:

2. The pattern effect
[ from earlier post ]

• News release: Paying for emissions we’ve already released

• Study: Greater committed warming after accounting for the pattern effect - by Chen Zhou et al.

and at: 

3. Clouds amplify global heating

• News release: Global satellite data shows clouds will amplify global heating

• Study: Observational evidence that cloud feedback amplifies global warming - by Paulo Ceppi et al.

discussed at:

4. Clouds net effect is more global heating

• News release: International analysis narrows range of climate’s sensitivity to CO2

• After 40 years, researchers finally see Earth's climate destiny more clearly

• The climate won’t warm as much as we feared – but it will warm more than we hoped - by Steven Sherwood et al.

• Study: An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence - by Steven Sherwood et al.

discussed at: 

5. Tipping point 478.6 ppm CO₂

• News release: Time Lag Between Intervention and Actual CO2 Decrease Could Still Lead to Climate Tipping Point

• Investigating climate tipping points under various emission reduction and carbon capture scenarios with a stochastic climate model - by Alexander Mendez et al. 

discussed at:

6. Temperatures looks set to keep rising

[ click on images to enlarge ]
An analysis by Jorgen Randers et al. points out that, even if all greenhouse gas emissions by people could stop immediately and even if the temperature anomaly could fall to 0.5°C above pre-industrial, greenhouse gas levels would start rising again after 2150 and keep rising for centuries to come.

Another analysis by Tapio Schneider et al., points out that solar geoengineering may not prevent strong warming from direct effects of CO₂ on stratocumulus cloud cover.

This means that the threat is even more menacing when including large methane releases that threaten to occur as temperatures keep rising in the Arctic and sediments at the seafloor of the Arctic Ocean threaten to get destabilized, resulting in the eruption of huge amounts of methane.

• An earth system model shows self-sustained thawing of permafrost even if all man-made GHG emissions stop in 2020 - by Jorgen Randers et al.

• Solar geoengineering may not prevent strong warming from direct effects of CO2 on stratocumulus cloud cover - by Tapio Schneider et al.

discussed at: