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We could slow global warming by making brighter clouds – but should we?

Geoengineering could help offset the effects of climate change, but is it wise to dabble in deliberately changing the climate?
Geoengineering could help offset the effects of climate change, but is it wise to dabble in deliberately changing the climate?
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An artist's rendition of a cloud-brightening ship concept, from the University of Washington
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An artist's rendition of a cloud-brightening ship concept, from the University of Washington
Geoengineering could help offset the effects of climate change, but is it wise to dabble in deliberately changing the climate?
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Geoengineering could help offset the effects of climate change, but is it wise to dabble in deliberately changing the climate?

Human activity has been messing with the Earth's atmosphere since the Industrial Revolution, and one controversial proposal is to attempt to slow the effects of climate change by… messing with the atmosphere. This week, two independent studies have examined the idea, one running computer simulations of a "cocktail" of techniques, while the other outlined a small-scale test to figure out how practical and safe the idea might be.

Geoengineering is the blanket term for a range of methods of tinkering with the delicate processes that regulate the climate. Suggested strategies include spraying small, reflective particles into the atmosphere to reduce the amount of solar energy that gets through. These particles, it's said, would mimic the effects of those blasted into the air from volcanic eruptions and rapidly cool the planet in a matter of years.

Of course, volcanic eruptions come with their share of hazards as well, polluting the air and water and in extreme cases triggering ice ages. It's unsurprising then that geoengineering is a sensitive topic. After all, unnatural airborne particles are what got us into this mess in the first place, so is it really wise to steer into the skid?

In a 2015 report, the US National Academies of Sciences, Engineering, and Medicine concluded that climate intervention technologies "pose considerable risks and should not be deployed at this time." But they didn't rule out the idea completely, instead recommending further research into the risks, challenges and benefits, and favoring studies that could improve our understanding of the climate in general.

Over the years, various research efforts have found both pros and cons. On the plus side, the diffused light from the Sun, as well as the high CO2 concentration in the air, can improve crop yields. But on the other hand, deflecting sunlight could undermine solar power systems and wouldn't address other problems like ocean acidification. Worse, there's no way to really know what other run-on consequences it could trigger.

An artist's rendition of a cloud-brightening ship concept, from the University of Washington
An artist's rendition of a cloud-brightening ship concept, from the University of Washington

With further research required, a team at the University of Washington is investigating marine cloud brightening, and has outlined a test to determine how feasible it might be. By spraying saltwater into the air, the process could make the clouds over the oceans "brighter" so they reflect more of the Sun's rays and, in keeping with the NAS's guidelines, also provide data on how clouds and aerosols interact.

"A major, unsolved question in climate science is: How much do aerosol particles cool the planet?," says Rob Wood, lead author of the study. "A controlled test would measure the extent to which we are able to alter clouds, and test an important component of climate models."

The researchers are already developing a nozzle that can reduce saltwater into tiny droplets and spray them high into the atmosphere by the trillions every second. The proposal outlines a three-year plan to produce the system, then conduct tests in a lab, before moving them outdoors and eventually offshore. These would all be small scale proof-of-concept runs, but if the technology works, scaled up versions could eventually be deployed over bigger patches of the ocean.

The second study comes out of Carnegie Institution for Science. In this project, climate scientists focused on two different methods of geoengineering: thinning cirrus clouds, which act like a blanket and trap heat close to Earth, and solar geoengineering, where sunlight is scattered by aerosol particles.

While both of these techniques could be effective at cooling the Earth, they run the risk of disrupting the precipitation cycle. Solar engineering, it was found, would reduce rainfall too much, while focusing on cirrus clouds doesn't do enough to slow the increase in rain that global warming causes.

So, the team ran "cocktail shaker" simulations to see what would happen if both were deployed at the same time. Interestingly enough, the study showed that warming would drop to pre-Industrial levels, while rainfall levels would on average stay the same. But the key word there is "average": where and how much rain fell would be drastically different.

"The same amount of rain fell around the globe in our models, but it fell in different places, which could create a big mismatch between what our economic infrastructure expects and what it will get," says Ken Caldeira, lead author of the study. "More complicated geoengineering solutions would likely do a bit better, but the best solution is simply to stop adding greenhouse gases to the atmosphere."

In the end, any kind of geoengineering technique may be too risky to roll out in the near future, but they should still be investigated as an emergency backup plan, in case climate change hits harder than expected.

"If the world cannot slow emissions or the effects of climate change are more extreme or occur sooner than expected, there may be demands to pursue additional climate-intervention technologies about which scientists need a better understanding," says Ralph J. Cicerone, National Academy of Sciences President. "Although riskier ideas to lessen the amount of energy absorbed from the sun should not be considered for deployment, they should be studied so that we can provide answers if someday these ideas begin to be considered in attempts to avert catastrophe."

The University of Washington study was published in the journal Earth's Future, while the Carnegie paper was published in Geophysical Research Letters.

Sources: University of Washington, Carnegie Institution for Science

14 comments
ThomasEdwardMiller
What if brightening clouds causes them to heat up less and rise less and reduce rain? I say, rather than brighten clouds, make more clouds. Here is my Rain Enhancement Steam Grid idea. Contrary to what many believe, there is a lot of moisture in hot fairly dry desert air. The weather report says that at 17h00 Monday 24 July the humidity in Cairo will be 30% and the temperature will be 37 deg C. This air will hold about 13 grams of water vapour in each cubic metre. If the temperature was 15 deg C and the relative humidity was 95% the air would hold only about 12 grams of water vapour per cubic metre. When air cools the relative humidity increases and the weather report says that at 23h00 on Monday 24 July the relative humidity in Cairo will be 65% and the temperature will be 29 deg C. Now if you heat air with a high relative humidity it does not have to rise far before clouds form. If you heat low relative humidity air, it has to rise high before clouds form and you have to heat it a lot to get it to rise so far. So here is the idea: Wait until the air cools and RH is high and then heat air a little to get it to rise and form clouds. My method to heat it is to have pipes with heated water containers at the ends and with holes in the pipes to let steam out. This will humidify and heat the air. Example. The weather report says that in Cairo on 28 July 2017 at 04h00 the RH will be 86% and the temperature will be 26 deg C. Using Espy's equation, if this 26 deg C air is heated to 28 deg C it only needs to rise 321 metres for clouds to form. By virtue of its temperature (T=28 deg C) it could rise 606 metres. So it can easily reach the height needed for clouds to form (used general sorts of lapse rates). I think it is an excellent idea to make clouds over the ocean, but not necessarily brighter clouds. By making spray clouds over the ocean one prevents a huge amount of energy being absorbed because most of the solar energy is absorbed by oceans and most of the energy falling on water is absorbed by it. Clouds absorb infrared readily and the clouds will absorb and evaporate. This will create more moisture (raise relative humidity) which is again a good thing as it helps prevent droughts. It will also help produce more clouds.
windykites
The article does not mention the subject of Chemtrails. High altitude planes appear to be spraying chemicals into the skies all over the world. The trails expand and last for many hours, eventually veiling the sky from horizon to horizon. There are plenty of photos online. I have a personal collection.
Brian M
@windykites - Yes the dimming effect, although not sure if that is the best way to solve the problem! Perhaps an easier option is reducing the greying of Antarctic ice by micro organisms or consider whitening ground areas, roofs etc. to reflect light. Always dangerous to tweak the natural process (as we have done), but global warming (and cooling) will happen eventually (as it has done in the past) without human intervention anyway, so maybe we will need to employ geoengineering some time in the future anyway!
highlandboy
The solution proposed would need to be implemented so that the saline solution does not precipitate on land. Rising salt and irrigation induced salinity is allready a problem in many areas whithout starting salary rain.
fen
Perhaps we need to mandate cities to be more reflective. Most of the "heating" of the world that humans seem to see, is jut because they are in a city and cities are local hotspots. If we make a real effort to turn to hydrogen made with green energy, carbon instead of aluminum in our cars, graphene in our chips instead of hard to mine materials, our cities reflecting the heat back... well I think we could go right to the edge of the world failing and save it.
Bob
Actually after 9/11 when most air traffic was grounded for several days, there were some studies made on significant temperature fluctuations due to the lack of contrails in the sky. I attempted to interest Richard Branson and a major airline in a jet fuel additive for day and night time global routes to take advantage of the contrail reflectivity and the effect it could have on global temperatures. Unfortunately, no one was interested. The vaporizing of sea water or trying to brighten clouds sounds interesting but would require a great investment and consumption of energy. My idea would have cost little and the planes would be flying the global routes anyway whether or not they used the additive. It would only take small deviations in the global routes and flying altitudes to increase the area covered and enhance its effects. Eventually, someone with money and influence will pick up on the idea. and make a fortune.
watersworm
Please : DO NOT !!!
EZ
I used to believe strongly in the "global warming" concept but after watching videos of famous scientists explain why it's a joke, I'm starting to be more open minded. The part about the atmosphere being on 5% CO2 was a grabber, as well as the track record of climate change that goes back thousands of years. From what I can gather, the climate is changing but it has always been changing, thus it's not caused by the industrial revolution. If there are any semi-opened minded "believers" still out there, it might be worth their time to watch a few. The other issue is that the scientist spokesman for the true believers refuses to participate in an open debate on the topic. That attitude is usually seen on the side that's hiding something.
Subtle
With the new trend to a Solar Minimum, the reduction in the Earth's magnetic field is allowing more cosmic rays through. This, in turn increases cloud formation and cooling. Less expensive if we leave climate alteration to Mother Nature
Douglas Bennett Rogers
Adding water to dry air has an enormous blocking effect on thermal emission that dwarfs the effect of CO2. Making more desert is the cheapest and most natural cure. This raises reflectivity and increases thermal emittance.