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Study finds sunshade geoengineering could improve crop yields

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January 26, 2012

A new study has concluded that sunshade geoengineering is more likely to improve crop yields than threaten them (Photo: Shutterstock)

A new study has concluded that sunshade geoengineering is more likely to improve crop yields than threaten them (Photo: Shutterstock)

In the face of potentially catastrophic effects on global food production, some have proposed drastic solutions to counteract climate change such as reflecting sunlight away from the Earth. A new study from the Carnegie Institution for Science examining the effects of sunshade geoengineering has concluded that such an approach would be more likely to improve food security than threaten it.

Just as large volcanoes cool the planet by ejecting massive amounts of small particles into the stratosphere, one sunshade geoengineering proposal would involve using high-flying airplanes to release small particles in the stratosphere that would scatter sunlight back into space. Just like the volcanic particles, these would fall back to Earth within a year so they would have to be constantly replenished to stop the planet heating back up. The fear is that such an approach could have unintended consequences for the climate, particularly in terms of its effect of precipitation.

While climate change in recent decades has been found to negatively affect crop yields in many regions, a new study led by Carnegie's Julia Pongratz is the first to examine the potential effect of geoengineering on food security. To assess the impact of sunshade geoengineering on crop yields, Pongratz's team, which included Carnegie's Ken Caldeira and Long Cao, as well as Stanford University's David Lobell, used two different climate models.

The team first simulated climates with CO2 levels similar to what exists today. A second set doubled CO2 levels to simulate levels that could be reached in several decades if current trends in fossil-fuel burning continued unabated. A third set doubled the levels of CO2, but with a layer of sulfate aerosols in the stratosphere deflecting about two percent on incoming sunlight away from Earth. The team then applied the simulated changes to crop models that are commonly used to project future yields.

They found that for both current and doubled CO2 levels, sunshade geoengineering would lead to increased crop yields in most regions. This because while such an approach would reduce temperatures by deflecting sunlight back into space, it wouldn't affect the levels of CO2.

"In many regions, future climate change is predicted to put crops under temperature stress, reducing yields. This stress is alleviated by geoengineering," Pongratz said. "At the same time, the beneficial effects that a higher CO2 concentration has on plant productivity remain active."

While the researchers say sunshade geoengineering would improve crop yields overall, the models also predict that some areas would be negatively affected. They also point out that there are other factors to consider, such as the deployment of such a system leading to political or military conflict, and the fact it ignores the acidification of the ocean, which is also caused by CO2 emissions. It would also affect the electricity-generation capabilities of solar power plants.

"The real world is much more complex than our climate models, so it would be premature to act based on model results like ours," Caldeira said. "But desperate people do desperate things. Therefore, it is important to understand the consequences of actions that do not strike us as being particularly good ideas."

"The climate system is not well enough understood to exclude the risks of severe unanticipated climate changes, whether due to our fossil-fuel emissions or due to intentional intervention in the climate system," says Pongratz. "Reducing greenhouse gas emissions is therefore likely a safer option than geoengineering to avert risks to global food security."

The Carnegie Institution for Science team's work was published online by Nature Climate Change.

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About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick
10 Comments

I read that by 2010, sea levels could potentially rise to cover up the US Midwest and Florida completely. According to The Canadian Progressive newspaper, climate change is likely to cause almost a billion deaths in 2011.

There was one measurable effect however; Al Gore\'s personal net worth went from $2M after the 2004 campaign to north of $800M today.

Todd Dunning

how about we learn to live with nature instead of trying to control it?

Artisteroi

So, if the CO2 doesn\'t change, why then are the crops effected by less sunlight? It would appear that it has nothing to do with the CO2 levels in the atmosphere, it most likely is a result of less light to evaporate the water that crops need to thrive.

I say that this \"seeding\" is a waste of time and money. We should be concentrating on desalination of ocean water, so we have plentiful water supplies for our growing earth.

As for the higher levels of CO2.... I, for one, do not believe that man is responsible for the critical levels, rather I think it is as a result of Mother nature, and her undersea furry. (Volcanoes, earthquakes, etc...)

Observer101

This article seems to ignore the most important question. Small particles of what will be sprayed into the stratosphere? Barium? Aluminum Oxide? Whatever is chosen it\'s doubtful that it will be conducive to healthy inhabitants on the planet.

Ian Atkinson

Geo-Engineering is already killing us. The planes are leaving Chemtrails over most of the main cities of the world. Aluminum is the main chemical causing Alzheimer\'s to reach all time highs, kids not developing correctly, & the soil is left too alkaline for plants to grow well. Levels of Aluminum at Mt. Shasta are supposed to be 0 parts per million; they are currently measured at 10,000 ppm and rising. Our water is toxic with it unless you have a filter to remove it. AND THAT\'S ONLY ONE OF THE 3 TOXIC CHEMICALS THEY SPRAY ALL THE TIME. LOOK UP & SEE YOUR DEMISE...UNLESS WE DO SOMETHING TO STOP THESE IDIOTS. See the video \"What in the World Are They Spraying?\"

Steve Alvarez

Sulfate aerosols are used in the simulations Ian.

Mark Keller

I\'m so tired of these stupid people thinking they run the world and the climate. CO2 is nearly twice as heavy as \'air\'. There is no CO2 in the upper atmosphere to reflect the heat and is why trees don\'t grow above 9,000 ft elevation.

bgroicahn

These questions and others disqualify aerosol releases.

Instead, very large inflatable satellites much like the original Echo One, should be placed in orbit to scatter sunlight away.

Think of the earth as a thermal system. The sun warms the system and like transparent goose down might, CO2 holds too much of that warmth at the surface. Since the earth cannot get rid of the sun\'s heat because of the increased CO2, the heat builds up. Most of the heat build up is going to unfreezing ice so far and raising the temperature of water. Glaciers and ice caps are melting everywhere on earth and the oceans are warming. Of course, the ice melt runoff cools the oceans back down, but the entire system is gradually accumulating heat.

Well, when balloons are orbited, they can stay up for more than just a year, plus they can be taken down easily or guided to other locations. Aerosols cannot be recalled like balloons can.

Orbital balloons can block light using very little mass. Such balloon satellites need only low pressure inflation and with no weather buffeting in space, their walls can be only a few molecules thick. That\'s lighter than aerosols. Twenty shuttle flights full of thousands of balloons would end global warming. We could even induce global cooling to get things back to historical temperature trends.

And what about CO2? Well, nothing. Increased CO2 will stay below 1% of the atmosphere at current trends for 100 years. More CO2 means more photosynthesis. Lower heating means higher crop yields, too. That means there would be food enough to feed all of humanity.

Once balloons were in place mostly above the equator, the ice in glaciers and ice caps would re-accumulate, so we would have our \'temperature buffer\' back, increasing planetary safety, too.

Experiments have shown that higher temperatures reduce rice yields. Higher CO2 increases rice yields. Lower just the temperature and we will have the best of both worlds.

TogetherinParis

Grow higher yield crops in the shade of a solar panel; dispersed light can be reflected in from the edges if too much light is blocked by a photovoltaic device.

HeavyDuty

Cane toads. The worst possible "solution" (to a problem that most likely doesn't exist) is to pump crap into the atmosphere. Duh. All you Eco people voted for Obama and for change, yet you won't accept climate change. You fail to remember that we are humans. We've tried to eradicate ourselves before but it never works.

Ethan Brush
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