Geoengineering Projects That Could Offset Global Warming

Geo-engineering is the large-scale engineering of the environment to combat the effects of climate change -- in particular to counteract the effects of increased carbon dioxide in the atmosphere. A number of schemes have been suggested including nutrient fertilisation of the oceans, cloud seeding, sunshades in space, stratospheric aerosol injections, and ocean pipes.

The first comprehensive assessment of the climate cooling potential of different geoengineering schemes has been carried out by researchers at the University of East Anglia (UEA).

Key findings include:

• Enhancing carbon sinks could bring CO₂ back to its pre-industrial level, but not before 2100 – and only when combined with strong mitigation of CO₂emissions
• Stratospheric aerosol injections and sunshades in space have by far the greatest potential to cool the climate by 2050 - but also carry the greatest risk
• Surprisingly, existing activities that add phosphorus to the ocean may have greater long-term carbon sequestration potential than deliberately adding iron or nitrogen
• On land, sequestering carbon in new forests and as ‘bio-char’ (charcoal added back to the soil) have greater short-term cooling potential than ocean fertilisation
• Increasing the reflectivity of urban areas could reduce urban heat islands but will have minimal global effect
• Other globally ineffective schemes include ocean pipes and stimulating biologically-driven increases in cloud reflectivity
• The beneficial effects of some geo-engineering schemes have been exaggerated in the past and significant errors made in previous calculations

“The realisation that existing efforts to mitigate the effects of human-induced climate change are proving wholly ineffectual has fuelled a resurgence of interest in geo-engineering,” said lead author Prof Tim Lenton of UEA’s School of Environmental Sciences.

“This paper provides the first extensive evaluation of their relative merits in terms of their climate cooling potential and should help inform the prioritisation of future research.”

Geo-engineering is the large-scale engineering of the environment to combat the effects of climate change – in particular to counteract the effects of increased CO₂ in the atmosphere.

A number of schemes have been suggested including nutrient fertilisation of the oceans, cloud seeding, sunshades in space, stratospheric aerosol injections, and ocean pipes.

“We found that some geoengineering options could usefully complement mitigation, and together they could cool the climate, but geoengineering alone cannot solve the climate problem,” said Prof Lenton.

Injections into the stratosphere of sulphate or other manufactured particles have the greatest potential to cool the climate back to pre-industrial temperatures by 2050.

However, they also carry the most risk because they would have to be continually replenished and if deployment was suddenly stopped, extremely rapid warming could ensue.

Using biomass waste and new forestry plantations for energy, and combusting them in a way that captures carbon as charcoal, which is added back to the soil as ‘bio-char’, could have win-win benefits for soil fertility as well as the climate.

This research was funded by the Natural Environment Research Council.

A new combined heat and power plant at UEA is pioneering this type of technology

Source: University of East Anglia. 

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Geoengineering Could Slow Down Global Water Cycle

A schematic representation of various geoengineering and carbon storage proposals. Credit: Diagram by Kathleen Smith/LLNL

As fossil fuel emissions continue to climb, reducing the amount of sunlight hitting the Earth would definitely have a cooling effect on surface temperatures.

However, a new study from Lawrence Livermore National Laboratory, led by atmospheric scientist Govindasamy Bala, shows that this intentional manipulation of solar radiation also could lead to a less intense global water cycle. Decreasing surface temperatures through "geoengineering" also could mean less rainfall.

The reduction in sunlight can be accomplished by geoengineering schemes. There are two classes: the so-called "sunshade" geoengineering scheme, which would mitigate climate change by intentionally manipulating the solar radiation on the earth's surface; the other category removes atmospheric CO₂ and sequesters it into the terrestrial vegetation, oceans or deep geologic formations.

In the new climate modeling study, which appears in the May 27-30 early online edition of the Proceedings of the National Academy of Sciences, Bala and his colleagues Karl Taylor and Philip Duffy demonstrate that the sunshade geoengineering scheme could slow down the global water cycle.

The sunshade schemes include placing reflectors in space, injecting sulfate or other reflective particles into the stratosphere, or enhancing the reflectivity of clouds by injecting cloud condensation nuclei in the troposphere. When CO₂ is doubled as predicted in the future, a 2 percent reduction in sunlight is sufficient to counter the surface warming.

This new research investigated the sensitivity of the global mean precipitation to greenhouse and solar forcings separately to help understand the global water cycle in a geoengineered world.

While the surface temperature response is the same for CO₂ and solar forcings, the rainfall response can be very different.

"We found that while climate sensitivity can be the same for different forcing mechanisms, the hydrological sensitivity is very different," Bala said.

The global mean rainfall increased approximately 4 percent for a doubling of CO₂and decreases by 6 percent for a reduction in sunlight in his modeling study.

"Because the global water cycle is more sensitive to changes in solar radiation than to increases in CO₂, geoengineering could lead to a decline in the intensity of the global water cycle" Bala said.

A recent study showed that there was a substantial decrease in rainfall over land and a record decrease in runoff and discharge into the ocean following the eruption of Mount Pinatubo in 1991. The ash emitted from Pinatubo masked some of the sunlight reaching the earth and therefore decreased surface temperatures slightly, but it also slowed down the global hydrologic cycle.

"Any research in geoengineering should explore the response of different components of the climate system to forcing mechanisms," Bala said.

For instance, Bala said, sunshade geoengineering would not limit the amount of CO₂ emissions. CO₂ effects on ocean chemistry, specifically, could have harmful consequences for marine biota because of ocean acidification, which is not mitigated by geoengineering schemes.

"While geoengineering schemes would mitigate the surface warming, we still have to face the consequences of CO₂ emissions on marine life, agriculture and the water cycle," Bala said.

Source: DOE/Lawrence Livermore 

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Can We Offset Global Warming By Geoengineering The Climate With Aerosols?

Volcano eruption on Reunion Island. Should humans deliberately mimic the effect of volcanic aerosols to try to offset global warming? Credit: iStockphoto/Julien Grondin

Concerned that energy system transformations are proceeding too slowly to avoid risks from dangerous human-induced climate change, many scientists are wondering whether geoengineering (the deliberate change of the Earth's climate) may help counteract global warming.

Sulfate aerosols, commonly released by volcanoes, serve to scatter incoming solar energy in the stratosphere, preventing it from reaching the surface. To investigate the feasibility of deliberately mimicking the effect of volcanic aerosols, Rasch et al. explore scenarios in which aerosol properties are varied to assess interactions with the climate system.

Through model simulations, they discover that, because stratosphere-troposphere exchange processes change with increasing levels of aerosols, about 50 percent more aerosols would have to be injected into the atmosphere than in the scenario where such processes stayed constant.

Further, almost double the level of aerosol loading is required to counteract greenhouse warming if aerosol particles are as large as those seen during volcanic eruptions. The authors caution that geoengineering methods to mask global warming may have serious environmental consequences that must be explored before any action is taken.

Journal reference: Exploring the geoengineering of climate using stratospheric sulfate aerosols: The role of particle size. Geophysical Research Letters (GRL) paper 10.1029/2007GL032179, 2008; http://dx.doi.org/10.1029/2007GL032179

Authors: Philip J. Rasch and Danielle B. Coleman: National Center for Atmospheric Research, Boulder Colorado, U.S.A.;Paul J. Crutzen: Max Plank Institute for Chemistry, Mainz, Germany; Also at Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, U.S.A.

Source: American Geophysical Union.

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Geoengineering our climate is not a 'quick fix'

The deliberate, large-scale intervention in the Earth's climate system is not a "quick fix" for global warming, according to the findings of the UK's first publicly funded studies on geoengineering. Credit: University of Leeds

The deliberate, large-scale intervention in the Earth's climate system is not a "quick fix" for global warming, according to the findings of the UK's first publicly funded studies on geoengineering.

The results of three projects -- IAGP, led by the University of Leeds; SPICE, led by the University of Bristol; and CGG, led by the University of Oxford -- are announced at an event held at The Royal Society, London, on 26 November 2014.

Professor Piers Forster, Professor of Physical Climate Change at the University of Leeds, and the principal investigator of the Integrated Assessment of Geoengineering Proposals (IAGP) project, said: "Our research shows that the devil is in the detail. Geoengineering will be much more expensive and challenging than previous estimates suggest and any benefits would be limited.

"For example, when simulating the spraying of sea salt particles into clouds to try to brighten them, we found that only a few clouds were susceptible and that the particles would tend to coagulate and fall out before reaching the cloud base."

In September 2009, The Royal Society published a report, Geoengineering the climate: science, governance and uncertainty. It influenced research worldwide, identified important gaps and called for a major UK funding programme into geoengineering. The IAGP and SPICE projects were funded the next year, and the CGG project followed in 2012.

IAGP is the UK's first interdisciplinary research study into the controversial issue of geoengineering. It has brought together a range of expertise -- climate modelling, philosophy and engineering -- in addition to understanding public perceptions, to assess geoengineering within wider societal values.

"Cleverly designed simulations create less necessity for real-world testing.. My favourite part of the research involved creating a virtual reality in which we tried to rescue Arctic sea ice by dumping sulphur dioxide into the atmosphere from Stratotanker aircraft flying out of Svalbard in Norway," said Professor Forster.

"Issues around monitoring and predicting the effects of our actions led to huge indecision and highlighted how challenging it would be to ever try and deploy these techniques in the real world."

Researchers working on the Stratospheric Particle Injection for Climate Engineering (SPICE) project took a different tack, but came to a similar cautionary conclusion.

Rather than running simulations, SPICE researchers used volcanoes as models to mimic the effect of a solar geoengineering proposal, in which sulphate aerosols are pumped into the atmosphere to reflect more sunlight back into space. This is a process that also naturally occurs due to particles emitted from volcanic eruptions.

Dr Matthew Watson, a reader in natural hazards from the University of Bristol, and principal investigator for the SPICE project, said: "Whilst it is clear that temperatures could be reduced during deployment, the potential for misstep is considerable. By identifying risks, we hope to contribute to the evidence base around geoengineering that will determine whether deployment, in the face of the threat of climate change, has the capacity to do more good than harm."

In addition to the feasibility of deployment, IAGP researchers organised workshops to gauge people's perceptions of geoengineering. Four public workshops were held in Birmingham, Cardiff, Glasgow and Norwich, and two stakeholder workshops in London, with representation from national government departments, civil society groups and industry.

The idea that geoengineering involves "messing with nature" was found to be a central theme in public discussion groups. The workshops also revealed that, of the geoengineering proposals discussed, carbon dioxide removal approaches were favoured over solar geoengineering approaches.

In both the public discussion groups and stakeholder workshops, climate change mitigation strategies, such as improving energy efficiency measures and scaling up renewable technologies, were preferred to geoengineering proposals.

Professor Forster said: "Consulting the public, policymakers and industry from the start told us that we should only consider geoengineering within the wider context of climate change mitigation and adaptation. Geoengineering is not a 'quick fix' alternative."

Dr Watson added: "Full scale deployment of climate engineering technologies will be the clearest indication that we have failed in our role as planetary stewards, but there is a point at which not deploying some technologies would be unethical."

Meanwhile, the Climate Geoengineering Governance (CGG) project is the world's first project to concentrate on the governance and regulatory challenges posed by both research and possible deployment.

The findings of the CGG project include the likelihood that cost estimates for major projects are unrealistic, and that geoengineering must be located firmly in the context of mitigation and adaptation to climate change.

Furthermore, CGG research has also unearthed a paradox: Geoengineering proposals that are technically the easiest to implement and have the quickest impact may be most difficult to govern, while those that are easiest to govern seem likely to be further away from effective large-scale deployment.

Professor Steve Rayner, the James Martin Professor of Science and Civilization at the University of Oxford, and principal investigator for the CGG project, concludes: "Take everything you hear both for and against geoengineering with a large grain of salt. Mostly it is too soon to know what any of these technology ideas would look like in practice or what would be their true cost and benefit.

"But it's almost certain that geoengineering will be neither a magic bullet nor Pandora's Box."

Source: University Of Leeds

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