The Unintended Consequences of Geoengineering a Cooler Atmosphere

Stimulating Ocean Phytoplankton Growth to Reduce Global Warming

A large phytoplankton bloom off the coast of Portugal. Image courtesy of Jacques Descloitres/NASA Goddard Space Flight Center.

In a newly published study, scientists from MIT reveal unintended consequences of an idea to stimulate ocean phytoplankton growth in order to geoengineer a cooler atmosphere.

Like the leaves of New England maples, phytoplankton, the microalgae at the base of most oceanic food webs, photosynthesize when exposed to sunlight. In the process, they absorb carbon dioxide from the atmosphere, converting it to carbohydrates and oxygen. Many phytoplankton species also release dimethyl sulfide (DMS) into the atmosphere, where it forms sulfate aerosols, which can directly reflect sunlight or increase cloud cover and reflectivity, resulting in a cooling effect. The ability of phytoplankton to draw planet-warming carbon dioxide (CO2) from the atmosphere and produce aerosols that promote further cooling has made ocean fertilization — through massive dispersal of iron sulfite and other nutrients that stimulate phytoplankton growth — an attractive geoengineering method to reduce global warming.

But undesirable climate impacts could result from such a large-scale operation, which would significantly increase emissions of DMS, the primary source of sulfate aerosol over much of the Earth’s surface, and a key player in the global climate system. Now, in a study published in Nature’s Scientific Reports, MIT researchers found that enhanced DMS emissions, while offsetting greenhouse gas-induced warming across most of the world, would induce changes in rainfall patterns that could adversely impact water resources and livelihoods in some regions.

“Discussions of geoengineering are gaining ground recently, so it’s important to understand any unintended consequences,” says Chien Wang, a co-author of the study and a senior research scientist at MIT’s Center for Global Change Science and the Department of Earth, Atmospheric, and Planetary Sciences. “Our work is the first in-depth analysis of ocean fertilization that has highlighted the potential danger of impacting rainfall adversely.”


Overview of new MIT research analyzing the idea of geoengineering a cooler atmosphere by stimulating the growth of ocean phytoplankton. Video: Benjamin Grandey

To investigate the impact of enhanced DMS emissions on global surface temperature and precipitation, the researchers used one of the global climate models used by the Intergovernmental Panel on Climate Change (IPCC), which simulates the evolution of and interactions among the ocean, atmosphere, and land masses. Running simulations that compared two scenarios, they found mixed results. In one simulation they implemented a scenario known as RCP4.5 that is used by the IPCC to project greenhouse gas concentrations, aerosol emissions, and land-use change based on policies that lead to moderate mitigation of greenhouse gas emissions over the course of the 21st century. They also used RCP4.5 in a second simulation, with one exception: DMS emissions from the ocean were increased to the maximum feasible levels, or about 2.5 times higher.

The simulations showed that enhanced DMS emissions would reduce the increase in average global surface temperature to half that of the RCP4.5 scenario, resulting in a net increase of 1.2 degrees Celsius by 2100. But the cost would be a substantial reduction in precipitation for some regions.

“Generally, our results suggest that the cooling effect associated with enhanced DMS emissions would offset warming across the globe, especially in the Arctic,” says the study’s first author, Benjamin Grandey, a senior postdoc in Wang’s group who configured the model simulations and analyzed the data. “Precipitation would also decline worldwide, and some parts of the world would be worse off. Europe, the Horn of Africa, and Pakistan may receive less rainfall than they have historically.”

Grandey and Wang warn that the lower rainfall could reduce water resources considerably, threatening the hydrological cycle, the environment, and livelihoods in the affected regions.

The researchers hope their investigation will inspire further studies of more realistic ocean fertilization scenarios, and of the potential impacts on marine ecosystems as well as human livelihoods. Further research will be needed, they say, to fully evaluate the viability of ocean fertilization as a geoengineering method to offset greenhouse gas-induced warming.

The study was funded by the Singapore National Research Foundation through the Singapore-MIT Alliance for Research and Technology Center for Environmental Sensing and Modeling, and grants from the National Science Foundation, Department of Energy, and Environmental Protection Agency.

Publication: B. S. Grandey & C. Wang, “Enhanced marine sulphur emissions offset global warming and impact rainfall,” Scientific Reports 5, Article number: 13055 (2015); doi:10.1038/srep13055

Source: Mark Dwortzan, MIT News

4 Comments on "The Unintended Consequences of Geoengineering a Cooler Atmosphere"

  1. Geoengineering, at present, is not a systemic solution. Geotherapy, using existing ecological systems to repair the damage we are already experiencing from climate change or even reverse it, is. There is a recent academic text which deals with some of these solutions based upon soil and agriculture, titled Geotherapy

    A conference on Restoring Water Cycles to Reverse Global Warming is happening on October 16-18

    Geotherapy may be a much more powerful idea than geoengineering even though it is still almost unknown.

  2. What if geoengineering is already being used?
    I didn’t believe in chemtrails either until in 1999 when I saw a military transport plane flying at too low an altitude to be putting out a contrail yet it was putting out a very big contrail over south Austin Texas. Kristen Meghan was an Air Force Bio-Environmental Engineer who had access to the lists of all materials being brought into the Air Force base as part of her safety checks. She noticed that large amounts of aluminum, barium and strontium particles were being brought into the base and being put into the jet fuel. When she went and complained to the Commanding Officer that this was toxic material that shouldn’t be used in such a way he got angry and told her unless she shut up about this that he had the power to have her committed to a mental hospital for six months. Her term of enlistment was to expire in a short time so she quit the military at that point and then began speaking out.
    Watch on Youtube “Shasta County Board of Supervisors Hearing on Chemtrails and Geoengineering July 15, 2014”. Lots of expert testimony contrary to what the government is saying on the issue.

    • That chemtrails nonsense again?

    • If they were putting those elements/metals into the jet fuel they would not need her to tell them because the engines would seize. You might want to get your information straight before you post stuff that makes no sense. How did you calculate the altitude of that plane in Texas? How did you calculate the atmospheric conditions at that altitude to come to your conclusion?

      In Shasta there was no expert testimony at all…just people who don’t know what they are talking about complaining about a faulty test that was done on some dirty sludge. A test that when done properly later on turned out to show no elevated levels of any of your metals.

      You are getting your information from bad websites I am assuming. Try to learn atmospheric science and stop reading the constantly debunked website geoengineeringwatch.

      Here is a website that shows how big a fraud Kristen is too: https://www.metabunk.org/kristen-meghan-former-us-air-force-whistle-blower.t1066/

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