Researchers study potential effects of geoengineering on global food supply

Jan 22, 2012

Carbon dioxide emissions from the burning of coal, oil, and gas have been increasing over the past decades, causing the Earth to get hotter and hotter. There are concerns that a continuation of these trends could have catastrophic effects, including crop failures in the heat-stressed tropics. This has led some to explore drastic ideas for combating global warming, including the idea of trying to counteract it by reflecting sunlight away from the Earth. However, it has been suggested that reflecting sunlight away from the Earth might itself threaten the food supply of billions of people.

New research led by Carnegie's Julia Pongratz examines the potential effects that geoengineering the climate could have on and concludes that sunshade geoengineering would be more likely to improve rather than threaten . Their work is published online by Nature Climate Change January 22.

Big volcanoes cool the planet by placing lots of small particles in the , but the particles fall out within a year and the planet heats back up. One proposal for cooling the planet is to use high-flying airplanes to constantly replenish a layer of small particles in the stratosphere that would scatter sunlight back to space. But such so-called sunshade geoengineering could have unintended consequences for climate, and especially for precipitation.

Although scientists know that climate change in recent decades has negatively impacted crop yields in many regions, the study by Pongratz and colleagues is the first to examine the potential effect of geoengineering on food security. Pongratz's team, which included Carnegie's Ken Caldeira and Long Cao, as well as Stanford University's David Lobell, used models to assess the impact of sunshade geoengineering on crop yields.

Using two different , they simulated climates with carbon dioxide levels similar to what exists today. A second set of simulations doubled carbon-dioxide levels – levels that could be reached in several decades if current trends in fossil-fuel burning continue unabated. A third set of simulations posited doubled carbon dioxide, but with a layer of sulfate aerosols in the stratosphere deflecting about 2% of incoming sunlight away from the Earth. The simulated climate changes were then applied to crop models that are commonly used to project future yields.

The team found that, in the model, sunshade geoengineering leads to increased crop yields in most regions, both compared with current conditions and with the future projection of doubled carbon dioxide on its own. This is because deflecting sunlight back to space reduces temperatures, but not CO2. "In many regions, future 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."

Even if the geoengineering would help crop yields overall, the models predict that some areas could be harmed by the geoengineering. And there are other risks that go beyond the direct impact on . For example, deployment of such systems might lead to political or even military conflict. Furthermore, these approaches do not solve the problem of ocean acidification, which is also caused by .

"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," Pongratz said. "Reducing greenhouse gas emissions is therefore likely a safer option than geoengineering to avert risks to global food security."

Explore further: Indians rally against climate change ahead of UN talks

Related Stories

Global sunscreen won't save corals

Jun 16, 2009

Emergency plans to counteract global warming by artificially shading the Earth from incoming sunlight might lower the planet's temperature a few degrees, but such "geoengineering" solutions would do little to stop the acidification ...

Climate change: Can geoengineering satisfy everyone?

Sep 15, 2010

Reflecting sunlight from the Earth by geoengineering would undoubtedly cool the climate, but would different countries agree on how much to reflect? Research by climate scientists at the University of Bristol ...

Cutting carbon dioxide helps prevent drying

Mar 24, 2011

Recent climate modeling has shown that reducing the concentration of carbon dioxide in the atmosphere would give the Earth a wetter climate in the short term. New research from Carnegie Global Ecology scientists Long Cao ...

Optimizing climate change reduction

Sep 16, 2010

Scientists at the Carnegie Institution's Department of Global Ecology have taken a new approach on examining a proposal to fix the warming planet. So-called geoengineering ideas—large-scale projects to change ...

Testing geoengineering

Oct 26, 2011

Solar radiation management is a class of theoretical concepts for manipulating the climate in order to reduce the risks of global warming caused by greenhouse gasses. But its potential effectiveness and risks are uncertain, ...

Recommended for you

Green dream: Can UN summit revive climate issue?

10 hours ago

Five years ago, the environment movement was in its heyday as politicians, actors, rock stars and protestors demanded a looming UN summit brake the juggernaut of climate change.

Rio's Olympic golf course in legal bunker

Sep 18, 2014

The return of golf to the Olympics after what will be 112 years by the time Rio hosts South America's first Games in 2016 comes amid accusations environmental laws were got round to build the facility in ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

mosahlah
not rated yet Jan 23, 2012
Add sulfur to JP8?