In order to get our warming climate under control, some forward thinkers say we should deploy any number of geoengineering schemes. But as the latest computer models show, these efforts would not only be futile — they'd probably result in a complete disaster.
Geoengineering techniques include such things as reflecting sunlight from space, ocean fertilization, making clouds more reflective, pumping deep cold nutrient-rich waters to the surface of oceans, and irrigating vast areas of the north African and Australian deserts to grow millions of trees. But after modeling five different schemes, researchers from the Helmholtz Centre for Ocean Research Kiel, Germany, concluded that, even when applied on a massive scale, the most that could be expected is a temperature drop of 8%.
But that's not the half of it; the potential side effects would be potentially disastrous. The Guardian reports on the findings:
Ocean upwelling, or the bringing up of deep cold waters, would cool surface water temperatures and reduce sea ice melting, but would unbalance the global heat budget, while adding iron filings or lime would affect the oxygen levels in the oceans. Reflecting the sun's rays into space would alter rainfall patterns and reforesting the deserts could change wind patterns and could even reduce tree growth in other regions.
In addition, say the scientists, two of the five methods considered could not be safely stopped. "We find that, if solar radiation management or ocean upwelling is discontinued then rapid warming occurs. If the other methods are discontinued, less dramatic changes occur. Essentially all of the CO2 that was taken up remains in the ocean."
Even the foresting of deserts on a massive scale could prove disastrous if the irrigation needed to grow the trees were stopped, they say. "The desert regions would eventually return to desert and the carbon that was stored in the plant biomass and soil would slowly be returned to the atmosphere through decay and respiration," says the paper.
Each of the five climate engineering methods considered has advantages and disadvantages but individually they are all limited, say the authors. "If CO2 emissions remain high, the climate engineering methods … should not be solely counted on to prevent warming. Our results suggest that CO2 mitigation seems the most effective way to prevent climate change. Climate engineering does not appear to be an alternative option, although it could be possibly used to complement mitigation," say the authors, who do not look at the ethical, economic, legal, political or technological feasibility of the five methods.
Damn, that's not good news. And neither is the suggestion that once we start geoengineering we won't be able to stop. What makes this all the more depressing is that we appear to lack the political and social will to do anything about climate change.
Read the study at Nature Communications: "Potential climate engineering effectiveness and side effects during a high carbon dioxide-emission scenario."