Jul 21, 2017

How clouds could be engineered to cool the Earth

Simon A. Eugster / Wikipedia

Scientists are actively exploring – on a theoretical basis – what it might take to cool the Earth if governments, businesses and individual actions collectively fail to do so in the next 15+ years. But, in nearly every case, the potential downside of such scientific actions aren't yet known, and there is no regulatory mechanism yet in place to govern or monitor the efforts, several leading scientists argue in Science this week.

Two approaches:

1. The leading geoengineering theory, according to scientists, is essentially a large science experiment on a global scale that mirrors what clouds do naturally. It would diminish the sun's warming effects by continuously injecting sulfur particles into the stratosphere, thus filtering out some of the radiation entering our atmosphere.

  • Pros: Most scientists agree it would change the temperature on Earth.
  • Cons: It could have a dramatic (and unintended) effect on the Earth's major water cycles, like the monsoon, that provide fresh water necessary for billions of people to live.
  • Other unknowns: how effective it might be, or how much it might cost. (Initial estimate are on the order of $20 billion a year for a century or more, they wrote.)

2. A second approach is to artificially create thin cirrus clouds at low-altitude that trap less heat and would cool the Earth.

  • Risks: These artificial clouds would attract moisture, and could upset the Earth's water cycles as well. And if this grand science experiment was done poorly, it could actually heat the planet instead of cool it.

What's needed: Janos Pasztor, the former climate policy lead at the United Nations (who now leads a geoengineering institute affiliated with Carnegie) argues that all of this means government leaders need to move quickly to understand the profound implications of both the research and its potential impacts. There is also an immediate risk that just one country, a small group of countries or even a very wealthy individual could unilaterally deploy a planet-wide solar radiation management scheme before anyone truly understands the potential risks.

Go deeper: Read our Expert Voices conversation on the topic.

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John Kelly defends James Mattis against Trump attacks

John Kelly in the White House in July 2017. Photo: Cheriss May/NurPhoto via Getty Images

Former White House chief of staff John Kelly defended James Mattis on Thursday after President Trump attacked the former defense secretary as "the world's most overrated general" and claimed on Twitter that he was fired.

What he's saying: “The president did not fire him. He did not ask for his resignation,” Kelly told the Washington Post in an interview. “The president has clearly forgotten how it actually happened or is confused."

Barr claims "no correlation" between removing protesters and Trump's church photo op

Attorney General Bill Barr said at a press conference Thursday that there was "no correlation" between his decision to order police to forcibly remove protesters from Lafayette Park and President Trump's subsequent visit to St. John's Episcopal Church earlier this week.

Driving the news: Barr was asked to respond to comments from Defense Secretary Mark Esper, who said Tuesday that he "did not know a photo op was happening" and that he does everything he can to "try and stay out of situations that may appear political."

Updates: Cities move to end curfews for George Floyd protests

Text reading "Demilitarize the police" is projected on an army vehicle during a protest over the death of George Floyd in Washington, D.C.. early on Thursday. Photo: Yasin Ozturk/Anadolu Agency via Getty Images

Several cities are ending curfews after the protests over the death of George Floyd and other police-related killings of black people led to fewer arrests and less violence Wednesday night.

The latest: Los Angeles and Washington D.C. are the latest to end nightly curfews. Seattle Mayor Jenny Durkan tweeted Wednesday night that "peaceful protests can continue without a curfew, while San Francisco Mayor London Breed tweeted that the city's curfew would end at 5 a.m. Thursday.