8 December 2015, The Conversation, Removing CO2 from the atmosphere won’t save us: we have to cut emissions now. Over 190 countries are negotiating in Paris a global agreement to stabilise climate change at less than 2℃ above pre-industrial global average temperatures. For a reasonable chance of keeping warming under 2℃ we can emit a further 865 billion tonnes of carbon dioxide (CO2). The climate commitments to reduce greenhouse gas emissions to 2030 are a first step, but recent analyses show they are not enough. So what are the options if we cannot limit emissions to remain within our carbon budget? Emitting more than the allowance would mean we have to remove carbon from the atmosphere. The more carbon we emit over the coming years, the more we will need to remove in future. In fact, out of 116 scenarios consistent with 2℃ published by the Intergovernmental Panel on Climate Change, 101 scenarios require the removal of CO2 from the atmosphere during the second half of this century. That’s on top of the large emission reductions required. So how do we remove carbon from the atmosphere? Several technologies have been proposed to this effect. These are often referred to as “negative emissions technologies” because the carbon is being removed from the atmosphere (in the opposite direction to emissions). In a study published today in Nature Climate Change, which is part of a broader release by the Global Carbon Project, we investigate how big a role these technologies could play in halting global warming. We find that these technologies might play a role in climate mitigation. However, the large scales of deployment currently used in most pathways that limit warming to 2℃ will be severely constrained by environmental and socio-economic factors. This increases the pressure to raise the level of ambition in reducing fossil fuel emissions now. Read More here
Tag Archives: geoengineering
5 November 2015, Climate News Network, ‘Dragon water’ could power the planet. The quest is on to develop new technology that can tap the intense heat deep below the Earth’s surface and supply the whole world with electricity. An ambitious project is being launched to drill deep into the Earth’s crust to harness super-heated “dragon water” that would generate massive quantities of renewable energy. Unlike traditional geo-thermal heat, which exploits hot rocks to produce steam for turbines, this project goes far deeper − to where the pressure and temperature are huge but the potential benefits are 10 times as great. There is an infinite amount of energy beneath the Earth’s crust. The problem is the technology to harness it. The European Union (EU) believes that deep drilling techniques developed by the oil industry can be adapted to extract the energy. It has earmarked €15.6 million for a project in which potentially the world’s most energy-rich geothermal well will be drilled at Larderello in Tuscany, Italy. Formidable challenge The technical challenges are formidable because of the intense heat and pressure that will turn steel brittle and wreck electrical equipment, so the plan is to develop engineering tools that can withstand the conditions. Iceland, which already exploits traditional geo-thermal energy successfully, has tried and failed to harness super-heated rock. But it has not given up, and a second attempt is being planned. The EU believes using oil company expertise in drilling deep wells will be the key to success. Read More here
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
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