Geoengineering

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Oxford Geoengineering Programme? Oxford Martin School

Will Developing Nations Hack the Climate? Kristan Uhlenbrock; UnDark; 18 Jul 2016

What if the poor and developing nations most vulnerable to climate change took matters into their own hands with geoengineering?

Solar geoengineering: Science fiction – or saviour? DAVID KEITH, EDWARD PARSON; GLOBE AND MAIL; 8 Dec 2017

People's initial reactions when they learn about the prospect of solar geoengineering typically involve some mix of horror and relief: horror at the prospect of a dangerous and uncontrolled technical fix, and relief that new technologies may offer the prospect of additional reductions in this century's severe climate risks.
But wherever your views fall on this spectrum, the case for serious research on solar geoengineering, and serious examination of its governance challenges, is compelling. Indeed, it is becoming increasingly likely that some form of climate engineering will be necessary to achieve the Paris target of limiting planetary heating to well below 2 C.
Solar geoengineering – one type of climate engineering – would involve reflecting a small amount of incoming sunlight back to space. The most plausible method is to use aircraft to make a fine mist of reflective material in the stratosphere, where it would act like a thin cloud reflecting a little sunlight back to space. Neither science fiction nor saviour, the goal of such intentional climate intervention would be to offset some of the climate changes caused by elevated greenhouse gases.
Most climate models agree that carefully managed solar geoengineering can reduce projected changes in both temperature and precipitation over nearly all the Earth's land surface. It can slow and likely reverse sea level rise, and provide some reduction to rapidly mounting threats to coral reefs, by slowing both rising temperatures and ocean acidification. It appears particularly effective at slowing current and projected increases in the strength of tropical hurricanes.
How should the world consider climate engineering? As a taboo, pushed aside from the centre of climate policy? Or, as a risky solution embraced all too quickly by opponents of emissions cuts? Between these polar extremes lies a wide range of opportunities for responsible exploration – and a great opportunity for Canada to exercise effective international leadership.

Carbon sequestration*

Aerosols

Devil’s Bargain Eric Holthaus; Grist; 8 Feb 2018

Air pollution from burning coal, driving cars, and using fire to clear land, among other activities, is the fourth-leading cause of death worldwide, killing about 5.5 million people each year. Nearly everybody is at risk, with roughly 92 percent of us living in places with dangerously polluted air. That alone makes reducing air pollution a necessary goal.
And yet we can’t live without aerosols, at least some of them. Natural aerosols — bits of dust, salt, smoke, and organic compounds emitted from plants — are an integral part of our planet’s atmosphere. Clouds probably wouldn’t be able to make rain without them. But as with greenhouse gases, human activity has resulted in too many aerosols (the excess is air pollution), with the bulk of the human-emitted aerosols lingering in the lower atmosphere, worsening their impact on our health. The result is a devil’s bargain: Aerosols are necessary for normal weather and help moderate rising temperatures, but they’re also killing us.
According to a new study, we might be locked in this deadly embrace. Research by an international team of scientists recently published in the journal Geophysical Research Letters says that the cooling effect of aerosols is so large that it has masked as much as half of the warming effect from greenhouse gases. So aerosols can’t be wiped out. Take them away and temperatures would soar overnight.
Turns out we have been unwittingly geoengineering for decades, and just like in the movies, it’s gone off the rails.

Climate Impacts From a Removal of Anthropogenic Aerosol Emissions B. H. Samset, M. Sand, C. J. Smith, S. E. Bauer, P. M. Forster, J. S. Fuglestvedt, S. Osprey, C.-F. Schleussner; Geophysical Research Letters; 24 Jan 2018

Abstract
Limiting global warming to 1.5 or 2.0°C requires strong mitigation of anthropogenic greenhouse gas (GHG) emissions. Concurrently, emissions of anthropogenic aerosols will decline, due to coemission with GHG, and measures to improve air quality. However, the combined climate effect of GHG and aerosol emissions over the industrial era is poorly constrained. Here we show the climate impacts from removing present-day anthropogenic aerosol emissions and compare them to the impacts from moderate GHG-dominated global warming. Removing aerosols induces a global mean surface heating of 0.5–1.1°C, and precipitation increase of 2.0–4.6%. Extreme weather indices also increase. We find a higher sensitivity of extreme events to aerosol reductions, per degree of surface warming, in particular over the major aerosol emission regions. Under near-term warming, we find that regional climate change will depend strongly on the balance between aerosol and GHG forcing.
Plain Language Summary
To keep within 1.5 or 2° of global warming, we need massive reductions of greenhouse gas emissions. At the same time, aerosol emissions will be strongly reduced. We show how cleaning up aerosols, predominantly sulfate, may add an additional half a degree of global warming, with impacts that strengthen those from greenhouse gas warming. The northern hemisphere is found to be more sensitive to aerosol removal than greenhouse gas warming, because of where the aerosols are emitted today. This means that it does not only matter whether or not we reach international climate targets. It also matters how we get there.

Polar ice

Can we refreeze the Arctic? Scientists are beginning to ask Chelsea Harvey; E&E News; 6 Mar 2018

Part one of a three-part series.
... researchers are turning their attention to the ever-more-vulnerable Arctic and Antarctic regions with increasingly ambitious ideas to protect them.
Recent proposals include the use of giant pumps to refreeze vanishing Arctic sea ice — an idea scientists say would not only preserve the landscape but also slow the region's rapid warming — and building huge mounds on the seafloor aimed at preventing warm water from melting glaciers. A number of these ideas were presented at the American Geophysical Union's conference in December, as reported by Oceans Deeply.
So far, they're just ideas. But the concept of polar geoengineering — physically manipulating conditions in the Arctic and Antarctic to try to protect the ice, if only temporarily — has been flickering within the scientific community for years.
In 2009, glaciologist Jason Box of the Geological Survey of Denmark and Greenland suggested covering sections of the Greenland ice sheet with reflective material, similar to the efforts in Europe's mountain glaciers. He went so far as to demonstrate the process on a small swath of the ice sheet in a project documented on the Discovery Channel's "Ways to Save the Planet" program.
It's uncertain whether this relatively simple idea — let alone more complex technological fixes — could ever be applied at a scale that would make a difference across the Arctic or Antarctic. Still, it's a field that some scientists believe is worth exploring, because what happens at the poles has such great potential to affect the rest of the world.

Albedo / radiation modification

Shipping in the Arctic to Cool Off the Planet ajdavis2004; Climate CoLab

With help from the multi-billion dollar trans-ocean shipping industry we can open Arctic-night ice-pack, and use these openings to grow and thicken ice to increase summer albedo. This intervention will keep the planet from accumulating excess energy, halting global warming, while providing habitat for Arctic sea life and year-round trade for Arctic human communities.

Will Dimming the Sun Cool the Planet and Help Crops? Annie Sneed; Scientific American; 8 Aug 2018

As Earth’s temperature steadily climbs and international action to curtail heat-trapping greenhouse gases falters, climate change poses such a dire threat that scientists are now seriously investigating geoengineering as a last-ditch attempt to cool the planet.
But deliberately manipulating Earth’s climate could obviously have unintended consequences, so “it’s very important that we study it before anyone tries to use it,” says Solomon Hsiang, a professor of public policy at the University of California, Berkeley. “We should know what we’re getting ourselves into.” Hsiang and a team of researchers aimed to find out with a new study that looks at how one type of proposed geoengineering—injecting tons of tiny particles into the atmosphere to deflect sunlight and shade the planet—would affect a very important system: agricultural crops.
A growing body of research suggests heat stress from global warming could crimp harvests—a major concern for global food security. For example, a study published in June found corn yields would drop overall and see more year-to-year variability as temperatures rise. Solar geoengineering, then, would seem like a potential way to ease the agrarian climate burden. It even offers the additional benefit of scattering the sun’s rays, creating the kind of diffuse light that many plants tend to prefer. But there is a potential snag: Plants would receive less light overall for photosynthesis. What remains unclear is which effect wins out, and so whether such geoengineering would ultimately hurt or help agriculture. Hsiang’s new study, published Wednesday in Nature, attempts to determine the overall effect.