No quick fix: Climate plan could destabilize Earth’s weather

With the climate heating up and carbon dioxide emissions still rising, scientists and policymakers are getting more serious about extreme plans to slow global warming.

One proposed climate fix is to alter the atmosphere to reflect some sunlight back into space and cool things down. This kind of large-scale intervention is called geoengineering.

Sounds simple enough, but Earth’s climate system is anything but simple. The wrong move could throw global weather patterns out of whack, harming everything from rainfall to crops.

A new study takes a close look at two of the most talked-about geoengineering options. One of them, the researchers say, could cause serious damage.

Proposed plans to block the Sun

Both options in the study focus on cutting the amount of sunlight that reaches the Earth’s surface. The first is called marine cloud brightening (MCB).

The strategy works by spraying sea salt particles into low clouds over the ocean, making them more reflective. The idea is to cool the surface below by bouncing more sunlight away.

The second option is called stratospheric aerosol injection (SAI). It involves releasing tiny sulfate particles high in the atmosphere to scatter sunlight before it even reaches the clouds.

Scientists chose to focus on how each of these methods might affect the Pacific Ocean – especially a powerful climate engine called the El Niño Southern Oscillation, or ENSO.

Massive changes in natural systems

ENSO is a natural cycle that shifts the distribution of warm water across the tropical Pacific every 2 to 7 years. It has global ripple effects.

When El Niño hits, California gets soaked with rain, while parts of Asia dry out. During La Niña, it’s the opposite – Asia gets stronger monsoons, and the Americas dry up.

Because this cycle affects global rainfall, agriculture, and even hurricane patterns, any plan that might change ENSO needs a close look.

That’s what led researchers at UC Santa Barbara to model what would happen if marine cloud brightening was used over the southeastern Pacific. What they found was shocking.

“Deploying MCB in the subtropical eastern Pacific dramatically reduces ENSO amplitude by approximately 61%,” the researchers wrote.

That’s a massive change for a system that usually moves slowly and resists disruption. “It’s hard to get ENSO to change by that much that quickly,” said Professor Samantha Stevenson, who co-authored the study.

A climate fix with big side effects

The problem with marine cloud brightening isn’t just that it cools the surface. It also makes the clouds hold on to water instead of raining it out. That makes the air below drier.

When that dry air moves westward across the ocean, it weakens the system that drives rainfall and wind patterns in the tropics.

In other words, ENSO starts to fall apart. The whole Pacific dries out. The sky gets windier and cooler. Ocean water upwells more often, which means colder surface temperatures. With the ENSO cycle flattened, global weather loses one of its key drivers.

Study lead author Chen Xing is a doctoral student at UCSB’s Bren School of Environmental Science & Management.

“The authors thought the proposals could have impacts, but we didn’t expect two-thirds of ENSO’s variance to disappear,” said Xing. “Don’t do MCB over the eastern Pacific Ocean because it might cause super strong chain reactions from ENSO’s disappearance.”

Cooling effects and cloud seeding

Interestingly, stratospheric aerosol injection didn’t have the same effect. It barely changed ENSO at all.

Why the difference? It seems to come down to how high up the particles go, and how evenly they’re spread. SAI’s sulfates get distributed across the upper atmosphere. That spreads out their cooling effect.

Marine cloud brightening, on the other hand, dumps sea salt close to the surface and keeps it in one place. That’s what causes trouble. But not every use of MCB would be a disaster.

“We’re not saying that all MCB is going to kill ENSO,” said Stevenson. “We’re just saying that this happens if you do it in this specific region.” Other areas might work better, but the same cooling effect would require more widespread cloud seeding.

Potential of blocking the Sun

Slowing climate change is important. But quick climate fixes could bring other problems, too.

Blocking sunlight would reduce photosynthesis – not just in forests and farms, but in the ocean. That’s a big deal. Tiny marine algae produce about 70% of the oxygen we breathe and form the base of the ocean’s food web.

The UCSB team plans to explore how these sunlight-blocking strategies might affect marine ecosystems. That includes fish, plankton, and everything that depends on them – including us.

Climate fixes are not created equal

“There’s nothing that compares to the speed with which ENSO would change in these MCB experiments,” said Stevenson. “It just does not naturally drop 60% in 10 years, even under climate change.”

Geoengineering might seem like a shortcut to a cooler planet. But as this study shows, even similar methods can have wildly different results.

“Two interventions can get to the same warming target globally and have extremely different regional climate impacts,” said Stevenson. “The most important question is, ‘Are we thinking of all of the potential consequences?’”

The full study was published in the journal Earth’s Future.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–