Geoengineering could slow down the global water cycle
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, with unpredictable impacts on agriculture and marine life.
There are basically two classes of geoengineering: 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, either via 'synthetic trees' into deep geologic formations or into oceans via algae blooms triggered by 'iron seeding' (dismissed by the IMO as 'currently not justified' because environmentally risky and shown by scientist not to work).
Biopact tracks such geoengineering proposals to compare their potential and risks with safe alternatives like 'bio-energy with carbon storage' (BECS) and biochar, which are capable of actively withdrawing CO2 from the atmosphere in a more natural way by relying on terrestrial plants.
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 (found to be extremely costly), injecting sulfate or other reflective particles into the stratosphere to emulate the effect of a massive volcanic eruption (found to be dangerous to the water cycle and could destroy the ozone layer), 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.
The 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. The team found that while climate sensitivity can be the same for different forcing mechanisms, the hydrological sensitivity is very different. The global mean rainfall increased approximately 4 percent for a doubling of CO2 and decreases by 6 percent for a reduction in sunlight in his modeling study.
energy :: sustainability ::sulphur :: bioenergy :: biochar :: sunlight :: geoengineering :: water cycle :: rainfall :: climate change ::
"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.
References:
G. Bala, P. B. Duffy, and K. E. Taylor, "Impact of geoengineering schemes on the global hydrological cycle", PNAS published May 27, 2008, 10.1073/pnas.0711648105
National Science Foundation: Injecting Sulfate Particles into Stratosphere Could Have Drastic Impact on Earth's Ozone Layer - 25 April 2008
Biopact: Capturing carbon with "synthetic trees" or with the real thing? - February 20, 2007
Biopact: International maritime body rejects risky ocean geoengineering - November 09, 2007
Biopact: WWF condemns Planktos Inc. iron-seeding plan in the Galapagos - June 27, 2007
Biopact: The end of a utopian idea: iron-seeding the oceans to capture carbon won't work - April 26, 2007
Biopact: Climate change and geoengineering: emulating volcanic eruption too risky - August 15, 2007
Biopact: Simulation shows geoengineering is very risky - June 05, 2007
There are basically two classes of geoengineering: 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, either via 'synthetic trees' into deep geologic formations or into oceans via algae blooms triggered by 'iron seeding' (dismissed by the IMO as 'currently not justified' because environmentally risky and shown by scientist not to work).
Biopact tracks such geoengineering proposals to compare their potential and risks with safe alternatives like 'bio-energy with carbon storage' (BECS) and biochar, which are capable of actively withdrawing CO2 from the atmosphere in a more natural way by relying on terrestrial plants.
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 (found to be extremely costly), injecting sulfate or other reflective particles into the stratosphere to emulate the effect of a massive volcanic eruption (found to be dangerous to the water cycle and could destroy the ozone layer), 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.
The 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. The team found that while climate sensitivity can be the same for different forcing mechanisms, the hydrological sensitivity is very different. The global mean rainfall increased approximately 4 percent for a doubling of CO2 and 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. - Govindasamy BalaA 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:
energy :: sustainability ::sulphur :: bioenergy :: biochar :: sunlight :: geoengineering :: water cycle :: rainfall :: climate change ::
"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.
References:
G. Bala, P. B. Duffy, and K. E. Taylor, "Impact of geoengineering schemes on the global hydrological cycle", PNAS published May 27, 2008, 10.1073/pnas.0711648105
National Science Foundation: Injecting Sulfate Particles into Stratosphere Could Have Drastic Impact on Earth's Ozone Layer - 25 April 2008
Biopact: Capturing carbon with "synthetic trees" or with the real thing? - February 20, 2007
Biopact: International maritime body rejects risky ocean geoengineering - November 09, 2007
Biopact: WWF condemns Planktos Inc. iron-seeding plan in the Galapagos - June 27, 2007
Biopact: The end of a utopian idea: iron-seeding the oceans to capture carbon won't work - April 26, 2007
Biopact: Climate change and geoengineering: emulating volcanic eruption too risky - August 15, 2007
Biopact: Simulation shows geoengineering is very risky - June 05, 2007
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