Uncertainty about climate change is not our friend

For a long time, there’s been one key part of the Earth system that, just maybe, could help us out a little bit with our global warming problem: Clouds.

Clouds are central to the climate because their white surfaces reflect sunlight back to space, keeping the planet cooler than it would be otherwise. But they also trap infrared or heat radiation and prevent it from escaping the Earth (among many other relevant effects). So if a changing climate also changes clouds – which scientists definitely expect to happen – that could be very important, and there have been prominent suggestions that this could all play out in such a way as to slow down climate change.

Clouds are “the biggest unknown in terms of the Earth’s radiation budget right now. They’ve been identified to be the largest source of uncertainty,” says Ivy Tan, a geoscientist at Yale who studies them. But uncertainty can cut both ways, and Tan is the lead author of a new study in Science suggesting that changes in clouds won’t actually protect us as much as we might have thought from the consequences of atmospheric carbon dioxide – which, in turn, means the Earth could warm more than otherwise expected.

Tan and her colleagues focused on a particular type of clouds called “mixed-phased,” which are comprised of both ice crystals and also some supercooled liquid water. Mixed-phased clouds are very common across the Earth, especially in cold and temperate regions, occurring, not surprisingly, higher in the air in mid-latitude regions and closer to the ground as you near the poles.

The reason they’re so important to climate is not just their abundance but their composition – the liquid parts of the cloud are better at deflecting sunlight away from the Earth, and liquid parts of these clouds are expected to increase, not surprisingly, as the climate warms. And that ought to be a negative feedback that makes global warming somewhat less bad than it would be otherwise.

“The more liquid you have in your cloud, the more reflective of shortwave radiation, or sunlight, it is,” Tan explains. “It’s a jucier cloud, it’s going to be thicker, it’s denser, so it’s going to reflect more sunlight back out to space than a cloud with ice would. The ice clouds are thinner, wispier, and more transparent to sunlight.”

But if you change the ratio of water to ice, you also change the strength of the feedback. And based on recent satellite observations, Tan and her colleagues – from Yale and Lawrence Livermore National Laboratory – argue that water has a higher prevalence in these clouds than many climate models assume or allow for. Their water content is “severely underestimated on a global scale” in such models, they write.

If the satellite observations are right, that means that as the climate warms, there will be less ice in these clouds to convert to liquid – and thus, less sunlight that will be reflected away from the Earth, leaving behind a warmer Earth.

The new paper therefore surmises that because of this cloud process, the climate will warm more than previously believed for a doubling of carbon dioxide levels in the atmosphere – by as much as 1.3 degrees Celsius. The paper thus implies that it may be necessary to up the value (or the range) for a critical and long-discussed parameter, known as the climate “sensitivity” for a doubling of CO2, which the U.N.’s Intergovernmental Panel on Climate Change most recently defined as “likely in the range 1.5°C to 4.5°C.” If Tan and her colleagues are proven right, then, the result could be to increase our expectations of future warming.

But that requires them to be proved right – several experts consulted by the Post had differing reactions to the new study.

The research is “a great example of the use of state-of-the-art satellite retrievals to constrain climate model process simulations, and this emerging constraint points towards a positive rather than a negative cloud brightness feedback and towards a higher climate sensitivity,” said George Tselioudis, a NASA climate expert who studies clouds and climate models, by email.

However, Anthony Del Genio, another NASA expert, was a bit more skeptical, noting that satellites may observe one thing on the outside of clouds, but that doesn’t mean what’s happening on the inside of them is the same. He also said that generally, the key processes involved are just very difficult for scientists to observe. “It is easy to say that climate models should fix this problem. But in practice it’s hard to fix because we don’t have the necessary data,” he said by email.

It is probably premature, then, to say that the new research means that scientists as a whole will now be concluding that thanks to a better understanding of clouds, the Earth is more sensitive to carbon dioxide than we thought – and will likely warm more than expected, or, at the high range of what’s currently expected. It’s rare that one study has such a sweeping impact.

“Headlines that scream ‘Scientists say sensitivity higher than thought!’ will not be justified,” says Gavin Schmidt, who directs NASA’s Goddard Institute for Space Studies. “This is one extra ingredient that needs to go into the hopper.”

Still, the new study clearly underscores that, while we don’t know everything about the climate yet, the things we don’t know could just as well harm us as help us.

“Our study suggests that the climate sensitivity range should be shifted upwards,” says Tan. “By how much, we don’t know exactly.”

Talk to us

> Give us your news tips.

> Send us a letter to the editor.

> More Herald contact information.

More in Local News

Trader Joe’s customers walk in and out of the store on Monday, Nov. 20, 2023 in Everett, Washington. (Olivia Vanni / The Herald)
New Trader Joe’s opens this week at Everett Mall

It’s a short move from a longtime location, essentially across the street, where parking was often an adventure.

Ian Bramel-Allen enters a guilty plea to second-degree murder during a plea and sentencing hearing on Wednesday, March 6, 2024, at Snohomish County Superior Court in Everett, Washington. (Ryan Berry / The Herald)
‘Deep remorse’: Man gets 17 years for friend’s fatal stabbing in Edmonds

Ian Bramel-Allen, 44, pleaded guilty Wednesday to second-degree murder for killing Bret Northcutt last year at a WinCo.

Firefighters respond to a small RV and a motorhome fire on Tuesday afternoon in Marysville. (Provided by Snohomish County Fire Distrct 22)
1 injured after RV fire, explosion near Marysville

The cause of the fire in the 11600 block of 81st Avenue NE had not been determined, fire officials said.

Ashton Dedmon appears in court during his sentencing hearing on Tuesday, March 5, 2024, at Snohomish County Superior Court in Everett, Washington. (Ryan Berry / The Herald)
Everett Navy sailor sentenced to 90 days for fatal hit and run

Ashton Dedmon crashed into Joshua Kollman and drove away. Dedmon, a petty officer on the USS Kidd, reported he had a panic attack.

A kindergarten student works on a computer at Emerson Elementary School on Wednesday, Feb. 28, 2024, in Everett, Washington. (Ryan Berry / The Herald)
‘¡Una erupción!’: Dual language programs expanding to 10 local schools

A new bill aims to support 10 new programs each year statewide. In Snohomish County, most follow a 90-10 model of Spanish and English.

Logo for news use featuring the Tulalip Indian Reservation in Snohomish County, Washington. 220118
Woman drives off cliff, dies on Tulalip Reservation

The woman fell 70 to 80 feet after driving off Priest Point Drive NW on Sunday afternoon.

Everett
Boy, 4, survives fall from Everett fourth-story apartment window

The child was being treated at Seattle Children’s. The city has a limited supply of window stops for low-income residents.

People head out to the water at low tide during an unseasonably warm day on Saturday, March 16, 2024, at Lighthouse Park in Mukilteo, Washington. (Ryan Berry / The Herald)
Everett shatters record high temperature by 11 degrees

On Saturday, it hit 73 degrees, breaking the previous record of 62 set in 2007.

Snohomish County Fire District #4 and Snohomish Regional Fire & Rescue respond to a motor vehicle collision for a car and pole. The driver was pronounced dead at the scene, near Triangle Bait & Tackle in Snohomish. (Snohomish County Sheriff’s Office)
Police: Troopers tried to stop driver before deadly crash in Snohomish

The man, 31, was driving at “a high rate of speed” when he crashed into a traffic light pole and died, investigators said.

Alan Dean, who is accused of the 1993 strangulation murder of 15-year-old Bothell girl Melissa Lee, appears in court during opening statements of his trial on Monday, March 18, 2024, at Snohomish County Superior Court in Everett, Washington. (Ryan Berry / The Herald)
31 years later, trial opens in Bothell teen’s brutal killing

In April 1993, Melissa Lee’s body was found below Edgewater Creek Bridge. It would take 27 years to arrest Alan Dean in her death.

Logo for news use featuring the municipality of Snohomish in Snohomish County, Washington. 220118
Man dies after crashing into pole in Snohomish

Just before 1 a.m., the driver crashed into a traffic light pole at the intersection of 2nd Street and Maple Avenue.

Bodies of two men recovered after falling into Eagle Falls near Index

Two men fell into the falls and did not resurface Saturday, authorities said. After a recovery effort, two bodies were found.

Support local journalism

If you value local news, make a gift now to support the trusted journalism you get in The Daily Herald. Donations processed in this system are not tax deductible.