Climate change means geoengineering under pressure to keep our CO2budgets under control ABC Science Pressure ramps up to pull CO2 from the sky with geoengineering tech | | | | | | | | | | | Pressure ramps up to pull CO2 from the sky with geoengineering tech Malcolm Sutton Experts say humanity has only 10 years to have large-scale carbon dioxide reduction schemes up and running if gl... | | | By Malcolm Sutton 7 October 2019 Reflective clouds created by human industries likeshipping can be seen from space. (Supplied: NASA) It's 2029 and every merchant ship in the world is fertilising the oceanwith iron — a last-ditch effort to draw carbon dioxide from the air as globalemissions near the point of no return. This global attempt to remove CO2 from the atmosphere has been 11 yearsin the making — since 2018, when the IPCC Global Warming of 1.5Cspecial report warned that emissions reductions alone wouldnot be enough to restrict global heating to 1.5 degrees Celsius. Removing carbon dioxide from the atmosphere would also be required. Key points: · Carbon dioxide removal techniques will be required to restrict globalheating to 1.5 degrees Celsius, according to the 2018 IPCC report · A UN Expert Group has reviewed potential marine geoengineeringtechniques to remove carbon dioxide from the atmosphere · Carbon removal at a global scale needs to be in effect within 10 years,experts said The hope is that the powdered iron will trigger a bloom of phytoplanktonthat will remove a gigatonne of CO2 from the atmosphere, by taking the carbonto the ocean floor when they die. There's evidence to support the concept — iron-stimulated blooms havebeen observed in nature for some time, sparked by events such as the 2010eruption of the Icelandic volcano Eyjafjallajökull, and Saharan desert dustplumes. In 2029, it's just one of a number of ideas about to be employed acrossthe planet to remove atmospheric carbon dioxide. A recent working group reviewed a wide range of proposedmarine geoengineering techniques. (Supplied: GESAMP) How best to remove CO2? Back in the present, and as signs of global warming continue to mount, apush is on to find ways to draw CO2 from the atmosphere. "It's now abundantly clear from the IPCC 1.5C special report thatif we're going to restrict warming to 2 degrees or less, then mitigation of thereduction of emissions on its own is not enough," said Philip Boyd,professor of marine biogeochemistry at the University of Tasmania. "We have to go beyond that andwe now have to intervene in the climate." Professor Boyd recently co-chaired a working group for the UN advisoryorganisation, Group of Experts on the Scientific Aspects of MarineEnvironmental Protection (GESAMP) that reviewed 27 potential marinegeoengineering techniques that had been studied or modelled to varying degreesworldwide. The group particularly focused on: · Iron fertilisation across 10 per cent of the Earth's oceans by utilisingevery merchant ship in the world · Adding lime to 10 per cent of the oceans to enhance alkalinity, increaseCO2 uptake and counter seawater acidity · Drawing up cool, nutrient-rich water from the depths with large pipes tocreate an artificial upwelling that provokes algal blooms while also coolingthe ocean's surface · Injecting liquified CO2 into the seabed in depressions and trencheswhere it can be stored for 1,000 years · Increasing the ocean's reflectivity by drawing up cold water to increaseArctic ice thickness, or by adding foams, micro-bubbles or reflective particlesto the surface · Brightening marine clouds by spraying fine seawater into low lyingstratocumulus clouds to increase their reflectivity and reduce surfacetemperatures · Farming seaweed on a large scale before entombing it deep in the oceanto sequester its carbon, or process it for biofuels In short, the group found a lot of potential. But more research,modelling and pilot programs are required, especially in consideration of themassive scales required. "What we are trying to do now is put some incentives out there,create some of these models for feedback," Professor Boyd said. "But right now I can't see any one of them sticking outhead-and-shoulders above the rest." Saharan dust storms over the Atlantic ocean fertiliseoceans with iron minerals. (Supplied: NASA) Old concepts and natural evidence The concept of using reflective particles to reduce warming was floatedas early as 1965, when scientific advisors to US President Lyndon Johnsonrecognised that increased CO2 in the atmosphere could bring about climatic change. They raised the prospect of spreading small reflective particles overlarge oceanic areas in an effort to reduce warming and inhibit hurricaneformation. More recently, scientists have investigated spraying fine seawater intolow-lying stratocumulus clouds above the Great Barrier Reef to make thembrighter and reflect more sunlight. The hope is that this will keepthe water temperature low enough to prevent coral bleaching. Scientists internationally have also been modelling a strategy to injectaerosols high into the stratosphere to replicate outcomesfrom the 1991 Mount Pinatubo eruption, in which reflective sulfuric aciddroplets drew down average global temperatures by 0.5C. A planet-sized sunshade? Should we try and turn thestratosphere into a giant global sunshade to stop Earth from overheating? But Andrew Lenton, an ocean carbon cycle modeler with the CSIRO, saidgeoengineering of this kind could have transnational consequences. "You're changing the balance,changing precipitation, and there is some really, really significant sideeffects that can go here," he said. Dr Lenton also pointed out that such techniques would not remove CO2from the atmosphere, which in high levels reduced pH levels at the ocean'ssurface and created acidity. "It might be like kids in a candy store with all these optionsavailable to us," he said. "But when you start to dig a bit deeper, everything has risk orpotential challenges associated with it." Humanity's CO2 budget · The IPCC in 2018 warned humanity could only emit another 420 gigatonnesif it is to have a 66 per chance of limiting global heating to 1.5 degreesCelsius · Uncertainties exist due to transient climate responses to high emissions,such as changes in the Earth's radiation absorption, thawing permafrost andwetlands releasing methane · The IPCC added that 'all analysed pathways' included a degree of carbondioxide removal to neutralise emissions from sources where no mitigation measureshad been identified Looking for ideas with multiple benefits Professor Boyd said there was a preference internationally fortechniques that had multiple benefits for the environment, along with thosethat did not step too far from the realms of financial reality. "There has been so muchsensationalism around this, with people talking about mirrors in space, orthousands of these bobbing pipes in the ocean," he said. "It's become a little bit sci-fi. "We really want to bring that back to earth by exploring work thatinvolves environmental co-benefits." Scientists have been studying the effects of acidificationon reefs. (Supplied: Aaron Takeo Ninokawa) This included the concept of "regenerative agriculture", whichcould see mined minerals with high CO2 absorption qualities worked intofarmland as fertiliser. "It comes at a low cost, you're sequestering carbon, you'refertilising, and you're also boosting the soil profile," Professor Boydsaid. "It might also be possible that you could further till that soil tobuild up its profile for biochar." Biochar is a carbon-rich material like charcoal that is produced frombiomass through slow pyrolysis rather than incineration, that is, heating inthe absence of oxygen rather than burning. Food and agricultural waste and even manure can be turned into biocharand added to soil, where it sequesters carbon and helps retain soil moistureand nutrients, subsequently bolstering crops when matched with the rightvarieties and conditions. Biochar, such as this collection created from bamboo, canalso help retain soil moisture. (ABC Sunshine Coast: Jacqueline Street) Just 10 years towork it out Trees also captureand store carbon dioxide — for as long as they stay alive, at least — and theirplanting in recent decades has been touted by commercial entities who claim tobe carbon neutral as a result. Dr Lenton cited a colleague who modelled growing trees on everyavailable piece of land worldwide under high emission models. "But she was not even able to get to a medium scenario [of globalemissions] by basically removing all the agricultural land and turning thatinto forest," he said. "The reality is, the scale isincredible, and there is competition for land. "You can't turn all sub-Saharan Africa into a forest and think thepeople there are going to be happy with that." Water availability could stymie plans to plant billions oftrees to capture carbon. ABC Rural: Kim Honan) Research published earlier this year, however, estimated there wasenough suitable unused land on Earth for re-forestration to store about 205 gigatonnes ofcarbon. "We can't just look at these things in isolation," Dr Lentonsaid. "We may potentially be able to plant a huge amount of forests butplanting eucalyptus, for example, requires a huge amount of water." He believes humanity has only 10 years to have large-scalecarbon dioxide reduction schemes up and running. These schemes would need to be making a significant dent in carbondioxide levels, as by that point CO2 emissions will likely have reached thelimit required to keep global warming to 1.5 degrees Celsius. But that, Dr Lenton said, was the root problem — one that casts a shadowover everything scientists were potentially fast-tracking to draw carbon fromthe sky. "If emissions are not going tobe falling globally, is this something even worth doing?" Bottom of Form Related articles · A planet-sized sunshade? It sounds far-fetched, but somescientists are seriously considering it · A billion hectares of new trees could pause theclimate-change clock · Acidic oceans could slow coral reef growth by a third · © 2019 ABC -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/1849369874.2973978.1570448787756%40mail.yahoo.com.
[geo] Climate change means geoengineering under pressure to keep our CO2 budgets under control ABC Science
'Robert Tulip' via geoengineering Mon, 07 Oct 2019 04:47:03 -0700
