Geoengineering

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Royal Society Report Concludes Geoengineering and its Consequences May be the Price for Failure to Act on Climate Change; Recommendations for “Plan B”

September 02, 2009

Preliminary overall evaluation of the geoengineering techniques considered in the report. From: Geoengineering the Climate (2009) Click to enlarge.

Unless emissions of carbon dioxide can be greatly reduced—i.e., unless future efforts to reduce greenhouse gas emissions are much more successful then they have been so far—potentially dangerous and unproven geoengineering will be required to cool the Earth this century, according to the latest report from the UK’s Royal Society. Geoengineering is defined as the deliberate large-scale intervention in the Earth’s climate system in order to moderate global warming.

The report, Geoengineering the climate: Science, governance and uncertainty, published by the Royal Society (the UK’s national academy of science), found that geoengineering technologies were very likely to be technically possible and some were considered to be potentially useful to augment the continuing efforts to mitigate climate change by reducing emissions. However, the report identified major uncertainties regarding their effectiveness, costs and environmental impacts.

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Study Finds That Plankton Blooms Do Not Send Atmospheric Carbon to the Deep Ocean; Weakens Iron Fertilization as Geo-Engineering Approach

May 07, 2009

Bishop and Wood with a recent version of the Carbon Explorer float. Photo: Roy Kaltschmidt, Lawrence Berkeley National Laboratory. Click to enlarge.

Oceanographers Jim Bishop and Todd Wood of the US Department of Energy’s Lawrence Berkeley National Laboratory have measured the fate of carbon particles originating in plankton blooms in the Southern Ocean, using data that deep-diving Carbon Explorer floats collected around the clock for well over a year. Their study reveals that most of the carbon from lush plankton blooms never reaches the deep ocean.

The results weaken the applicability of the simplest version of the Iron Hypothesis as a geo-engineering approach to climate change. Iron Hypothesis adherents suggest global warming can be slowed or even reversed by fertilizing plankton with iron in regions that are iron-poor but rich in other nutrients like nitrogen, silicon, and phosphorus. The Southern Ocean is one of the most important such regions.

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Researchers Evaluate Climate Cooling Potential of Different Geoengineering Schemes

January 27, 2009

Schematic overview of the climate geoengineering proposals considered. From Vaughan and Lenton (2009). Click to enlarge.

Researchers at the University of East Anglia (UEA) have carried out the first comprehensive assessment of the relative merits of different geoengineering schemes in terms of the climate cooling potential. Their paper appears in the journal Atmospheric Chemistry and Physics Discussions.

Climate geoengineering proposals seek to combat the effects of climate change—in particular to counteract the effects of increased CO₂ in the atmosphere. There are two basic approaches proposed: reducing the atmospheric absorption of incoming solar (shortwave) radiation, or removing CO₂ from the atmosphere and transferring it to long-lived reservoirs, thereby increasing outgoing longwave radiation.

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Aerosols Can Either Increase or Decrease Rainfall Based on Local Environmental Conditions

September 07, 2008

Evolution of deep convective clouds developing in the pristine (top) and polluted (bottom) atmosphere. Click to enlarge. Source: AAAS

An international team of scientists, headed by Prof. Daniel Rosenfeld of the Institute of Earth Sciences at the Hebrew University of Jerusalem, has concluded that air pollution can either increase or decrease rainfall, depending on local environmental conditions. The determination of this issue is one with significant consequences in an era of climate change and specifically in areas suffering from manmade pollution and water shortages, including Israel, according to the researchers. A paper on the work appears in the 5 September issue of the journal Science.

Aerosols serve as cloud condensation nuclei (CCN) and thus have a substantial effect on cloud properties and the initiation of precipitation. Large concentrations of human-made aerosols have been reported to both decrease and increase rainfall as a result of their radiative and CCN activities. At one extreme, pristine tropical clouds with low CCN concentrations rain out too quickly to mature into long-lived clouds. On the other hand, heavily polluted clouds evaporate much of their water before precipitation can occur, if they can form at all given the reduced surface heating resulting from the aerosol haze layer.

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