18 August 2015, Atmospheric Chemistry and Physics, Abstract. The injection of sulfur dioxide (SO2) into the stratosphere to form an artificial stratospheric aerosol layer is discussed as an option for solar radiation management. The related reduction of radiative forcing depends upon the injected amount of sulfur dioxide, but aerosol model studies indicate a decrease in forcing efficiency with increasing injection rate. None of these studies, however, consider injection rates greater than 20 Tg(S) yr−1. But this would be necessary to counteract the strong anthropogenic forcing expected if “business as usual” emission conditions continue throughout this century. To understand the effects of the injection of larger amounts of SO2, we have calculated the effects of SO2 injections up to 100 Tg(S) yr−1. We estimate the reliability of our results through consideration of various injection strategies and from comparison with results obtained from other models. Our calculations show that the efficiency of such a geoengineering method, expressed as the ratio between sulfate aerosol forcing and injection rate, decays exponentially. This result implies that the sulfate solar radiation management strategy required to keep temperatures constant at that anticipated for 2020, while maintaining business as usual conditions, would require atmospheric injections of approximately 45 Tg(S) yr−1 (±15 % or 7 Tg(S) yr−1) at a height corresponding to 60 hPa. This emission is equivalent to 5 to 7 times the Mt. Pinatubo eruption each year. Read More here
Tag Archives: geoengineering
3 August 2015, Potsdam Institute, CO2 removal cannot save the oceans – if we pursue business as usual. Greenhouse-gas emissions from human activities do not only cause rapid warming of the seas, but also ocean acidification at an unprecedented rate. Artificial carbon dioxide removal (CDR) from the atmosphere has been proposed to reduce both risks to marine life. A new study based on computer calculations now shows that this strategy would not work if applied too late. CDR cannot compensate for soaring business-as-usual emissions throughout the century and beyond, even if the atmospheric carbon dioxide (CO2) concentration would be restored to pre-industrial levels at some point in the future. This is due to the tremendous inertia of the ocean system. Thus, CDR cannot substitute timely emissions reductions, yet may play a role as a supporting actor in the climate drama. Ocean acidification affects the shells of plankton like Pteropods. “Geoengineering measures are currently being debated as a kind of last resort to avoid dangerous climate change – either in the case that policymakers find no agreement to cut CO2 emissions, or to delay the transformation of our energy systems,” says lead-author Sabine Mathesius from GEOMAR Helmholtz Centre for Ocean Research Kiel and the Potsdam Institute for Climate Impact Research (PIK). “However, looking at the oceans we see that this approach carries great risks.” In scenarios of timely emissions reductions, artificially removing CO2can complement efforts. “Yet in a business-as-usual scenario of unabated emissions, even if the CO2 in the atmosphere would later on be reduced to the preindustrial concentration, the acidity in the oceans could still be more than four times higher than the preindustrial level,” says Mathesius. “It would take many centuries to get back into balance with the atmosphere.” Read More here
4 May 2015, Climate News Network: No green light for whitening Arctic’s melting ice. Scientists pour cold water on the idea of preventing ice melt by using geo-technology to keep it white so that it reflects sunlight and stays frozen. Yet another geo-engineering solution to climate change has been proven potentially useless: even if you could paint the Arctic white, the world would still get warmer. Read More here