Paths to geoengineering


in Economics, Geek stuff, Politics, Science, The environment

Green paint, red rust

For a number of reasons, geoengineering is all over the news. The basic idea is to counteract the effects of climate change induced by greenhouse gasses. This can be accomplished in two basic ways. One is to use a separate mechanism to reduce the amount of energy the Earth absorbs from the sun. Orbiting mirrors and sulfate injection seek to do this. This approach is not ideal, partly because it would cause unknown side effects and partly because it would not stop the oceans from becoming more acidic. A more appealing route focuses on actively removing greenhouse gasses from the atmosphere.

The first way to do this is to encourage the growth of biomass. This is relatively easy, but has limited potential. Biomass is like a giant carbon cushion: it can be thick or thin, but it cannot keep growing forever. Increasing the amount of biomass on Earth could draw down the amount of CO2 in the atmosphere a bit, but only if we also manage to cut our greenhouse gas emissions to practically zero.

The second way – mentioned before – is to draw greenhouse gasses from the air and bury them, using carbon capture and storage technology (CCS). This could be done in two basic ways: (a) draw carbon dioxide (CO2) directly from the air and bury it or (b) grow biomass, burn it, collect the CO2, and bury that. The major limitations here are cost and technology. It remains unclear whether CCS can be made safe, effective, and affordable. It is also unclear whether it could be ramped up to a big enough scale to stop catastrophic climate change, in the absence of strong mitigation action.

The third option is to enhance the weathering of rocks. In the long term, this is where atmospheric CO2 actually ends up going. Some people are talking about speeding up the process, using various suitable types of rock and various mechanisms for increasing its rate of reaction with atmospheric CO2. Once again, the uncertainties concern scale and cost.

The three options that actually remove CO2 from the atmosphere are much more appealing than options that try to interrupt incoming sunlight. Each acts directly on the cause of anthropogenic warming, rather than trying to counter it by proxy. This is a bit like removing poison from a person’s body, as opposed to administering a supposed antidote with unknown effectiveness and side effects.

It remains unknown whether there will ever be a point where geoengineering is less costly per tonne of CO2 than various mitigation approaches. Right now, there are certainly greater opportunities in areas like energy efficiency and building design. That being said, research into CO2-removing technologies strikes me as having merit. They may eventually prove economically comparable to more expensive mitigation options; they may allow us to counteract activities that inevitably produce emissions, such as air travel; and they could give us some last-ditch options, if we find ourselves experiencing abrupt, catastrophic, or runaway climate change as a result of past emissions.

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{ 10 comments… read them below or add one }

R.K. September 9, 2009 at 11:45 am

The danger is that people will either invest heavily in geoengineering approaches that prove ineffective, or they will assume that geoengineering will work cheaply, with no bad side effects, and then use it as an excuse to not mitigate.

Geoengineering might be an example of something best studied in secret.

R.K. September 9, 2009 at 11:47 am

Then again, only widely publicized studies illustrating the difficulties and limitations will allow people to argue effectively against those who assert that geoengineering will easily solve the climate problem.

. September 14, 2009 at 4:44 pm

Now, what’s the best way to suck CO2 from thin air? I’ll discuss four technologies for building the giant vacuum cleaner:

A. chemical pumps;
B. trees;
C. accelerated weathering of rocks;
D. ocean nourishment.

Tristan February 8, 2010 at 7:07 pm
Milan February 8, 2010 at 7:18 pm

A space mirror would be a lot easier to build than a huge atmosphere-sucking maid robot.

. March 26, 2010 at 6:36 pm

Cooling the Planet With a Bubble Bath

“A Harvard University physicist has come up with a new way to cool parts of the planet: pump vast swarms of tiny bubbles into the sea to increase its reflectivity and lower water temperatures. ‘Since water covers most of the earth, don’t dim the sun,’ says the scientist, Russell Seitz, speaking from an international meeting on geoengineering research. ‘Brighten the water.’ From ScienceNOW: ‘Computer simulations show that tiny bubbles could have a profound cooling effect. Using a model that simulates how light, water, and air interact, Seitz found that microbubbles could double the reflectivity of water at a concentration of only one part per million by volume. When Seitz plugged that data into a climate model, he found that the microbubble strategy could cool the planet by up to 3C. He has submitted a paper on the concept he calls “Bright Water” to the journal Climatic Change.'”

. January 22, 2013 at 12:04 pm

Researchers analyse ‘rock dissolving’ method of geoengineering

The benefits and side effects of dissolving particles in our ocean’s surfaces to increase the marine uptake of carbon dioxide (CO2), and therefore reduce the excess amount of it in the atmosphere, have been analysed in a new study. The study, published Jan. 22 in IOP Publishing’s journal Environmental Research Letters, assesses the impact of dissolving the naturally occurring mineral olivine and calculates how effective this approach would be in reducing atmospheric CO2.

The researchers, from the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, calculate that if three gigatonnes of olivine were deposited into the oceans each year, it could compensate for only around nine per cent of present day anthropogenic CO2 emissions.

This long discussed ‘quick fix’ method of geoengineering is not without environmental drawbacks; the particles would have to be ground down to very small sizes (around one micrometre) in order to be effective. The grinding process would consume energy and therefore emit varying amounts of CO2, depending on the sort of power plants used to provide the energy.

. August 25, 2013 at 9:19 pm

Rocks Can Restore Our Climate … After 300,000 Years

July 26, 2013 — A study of a global warming event that happened 93 million years ago suggests that the Earth can recover from high carbon dioxide emissions faster than thought, but that this process takes around 300,000 years after emissions decline.Scientists from Oxford University studied rocks from locations including Beachy Head, near Eastbourne, and South Ferriby, North Lincolnshire, to investigate how chemical weathering of rocks ‘rebalanced’ the climate after vast amounts of carbon dioxide (CO2) were emitted during more than 10,000 years of volcanic eruptions

In chemical weathering CO2 from the atmosphere dissolved in rainwater reacts with rocks such as basalt or granite, dissolving them so that this atmospheric carbon then flows into the oceans, where a large proportion is ‘trapped’ in the bodies of marine organisms.

The team tested the idea that, as CO2 warms the planet, the reactions involved in chemical weathering speed up, causing more CO2 to be ‘locked away’, until, if CO2 emissions decline, the climate begins to cool again. The Oxford team looked at evidence from the ‘Ocean Anoxic Event 2’ in the Late Cretaceous when volcanic activity spewed around 10 gigatonnes of CO2 into the atmosphere every year for over 10,000 years. The researchers found that during this period chemical weathering increased, locking away more CO2 as the world warmed and enabling the Earth to stabilise to a cooler climate within 300,000 years, up to four times faster than previously thought.

. August 25, 2013 at 9:27 pm

Lithium isotope evidence for enhanced weathering during Oceanic Anoxic Event 2

The Ocean Anoxic Event 2 (OAE2) about 93.5 million years ago was marked by high atmospheric CO2 concentration, rapid global warming and marine anoxia and euxinia. The event lasted for about 440,000 years and led to habitat loss and mass extinction. The marine anoxia is thought to be linked to enhanced biological productivity, but it is unclear what triggered the increased production and what allowed the subsequent rapid climate recovery. Here we use lithium isotope measurements from carbonates spanning the interval including OAE2 to assess the role of silicate weathering. We find the lightest values of the Li isotope ratio (δ7Li) during OAE2, indicating high levels of weathering—and therefore atmospheric CO2 removal—which we attribute to an enhanced hydrological cycle. We use a geochemical model to simulate the evolution of δ7Li and the Ca, Sr and Os isotope tracers. Our simulations suggest a scenario in which the eruption of a large igneous province led to high atmospheric CO2 concentrations and rapid global warming, which initiated OAE2. The simulated warming was accompanied by a roughly 200,000 year pulse of accelerated weathering of mafic silicate rocks, which removed CO2 from the atmosphere. The weathering also delivered nutrients to the oceans that stimulated primary productivity. We suggest that this process, together with the burial of organic carbon, allowed the rapid recovery and stabilization from the greenhouse state.

. August 26, 2013 at 5:22 pm

Nature Climate Change | Perspective
Deliberating stratospheric aerosols for climate geoengineering and the SPICE project

Increasing concerns about the narrowing window for averting dangerous climate change have prompted calls for research into geoengineering, alongside dialogue with the public regarding this as a possible response. We report results of the first public engagement study to explore the ethics and acceptability of stratospheric aerosol technology and a proposed field trial (the Stratospheric Particle Injection for Climate Engineering (SPICE) ‘pipe and balloon’ test bed) of components for an aerosol deployment mechanism. Although almost all of our participants were willing to allow the field trial to proceed, very few were comfortable with using stratospheric aerosols. This Perspective also discusses how these findings were used in a responsible innovation process for the SPICE project initiated by the UK’s research councils.

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