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Showing results 1 - 10 of 10
Author(s): Schmidt H, Alterskjær K, Karam DB, Boucher O, Jones A, Kristjansson JE, Niemeier U, Schulz M, Aaheim A, Benduhn F, Lawrence MG, Timmreck C
Published: March, 2012
Publisher: Earth System Dynamics Discussions
DOI: 10.5194/esdd-3-31-2012
Tags: Stratospheric Aerosols, Cloud Brightening, Climate Modelling
URL: http://www.earth-syst-dynam-discuss.net/3/31/2012/esdd-3-31-2012.html
Abstract: In this study we compare the response of four state-of-the-art Earth system models to climate engineering under scenario G1 of the GeoMIP and IMPLICC model intercomparison projects. In G1, the radiative forcing from an instantaneous quadrupling of the CO2 concentration, starting from the preindustrial level, is balanced by a reduction of the solar constant. Model responses to the two counteracting forcings in G1 are compared to the preindustrial climate in terms of global means and regional patterns and their robustness. While the global mean surface air temperature in G1 remains almost unchanged, the meridional temperature gradient is reduced in all models compared to the control simulation. Another robust response is the global reduction of precipitation with strong effects in particular over North and South America and northern Eurasia. It is shown that this reduction is only partly compensated by a reduction in evaporation so that large continental regions are drier in the engineered climate. In comparison to the climate response to a quadrupling of CO2 alone the temperature responses are small in experiment G1. Precipitation responses are, however, of comparable magnitude but in many regions of opposite sign.
Author(s): Schmidt H, Alterskjær K, Bou Karam D, Boucher O, Jones A, Kristjánsson JE, Niemeier U, Schulz M, Aaheim A, Benduhn F, Lawrence M, Timmreck C
Published: January, 2012
Publisher: Earth System Dynamics
DOI: 10.5194/esd-3-63-2012
Tags: Space Reflectors, Stratospheric Aerosols, Cloud Brightening, Climate Modelling
URL: http://www.earth-syst-dynam.net/3/63/2012/esd-3-63-2012.html
Abstract: In this study we compare the response of four state-of-the-art Earth system models to climate engineering under scenario G1 of two model intercomparison projects: GeoMIP (Geoengineering Model Intercomparison Project) and IMPLICC (EU project "Implications and risks of engineering solar radiation to limit climate change"). In G1, the radiative forcing from an instantaneous quadrupling of the CO2 concentration, starting from the preindustrial level, is balanced by a reduction of the solar constant. Model responses to the two counteracting forcings in G1 are compared to the preindustrial climate in terms of global means and regional patterns and their robustness. While the global mean surface air temperature in G1 remains almost unchanged compared to the control simulation, the meridional temperature gradient is reduced in all models. Another robust response is the global reduction of precipitation with strong effects in particular over North and South America and northern Eurasia. In comparison to the climate response to a quadrupling of CO2 alone, the temperature responses are small in experiment G1. Precipitation responses are, however, in many regions of comparable magnitude but globally of opposite sign.
Author(s): Robock A, Kravitz B, Boucher O
Published: June, 2011
Publisher: Eos
DOI: 10.1029/2011EO230008
Tags: Research, Stratospheric Aerosols, Climate Modelling
URL: http://www.agu.org/pubs/crossref/2011/2011EO230008.shtml
Abstract: The term “geoengineering” refers to deliberate large-scale anthropogenic modification of the climate. The most frequently discussed type of geoengineering, using socalled solar radiation management (SRM) to counteract global warming, has been to try to create a stratospheric aerosol cloud to reflect solar radiation. Stratospheric aerosols have the potential to cool the planet within a few years, as demonstrated by large natural volcanic eruptions. If a stratospheric aerosol layer could be maintained artificially, it could reduce or reverse some of the impacts of climate change, such as ice sheet melting, sea level rise, and thawing of permafrost.
Author(s): Kravitz B, Robock A, Boucher O, Schmidt H, Taylor KE, Stenchikov GL, Schulz M
Published: January, 2011
Publisher: Atmospheric Science Letters
DOI: 10.1002/asl.316
Tags: Stratospheric Aerosols, Climate Modelling
URL: http://onlinelibrary.wiley.com/doi/10.1002/asl.316/abstract
Abstract: To evaluate the effects of stratospheric geoengineering with sulphate aerosols, we propose standard forcing scenarios to be applied to multiple climate models to compare their results and determine the robustness of their responses. Thus far, different modeling groups have used different forcing scenarios for both global warming and geoengineering, complicating the comparison of results. We recommend four experiments to explore the extent to which geoengineering might offset climate change projected in some of the Climate Model Intercomparison Project 5 experiments. These experiments focus on stratospheric aerosols, but future experiments under this framework may focus on different means of geoengineering.
Author(s): Jones A, Haywood J, Boucher O
Published: September, 2010
Publisher: Atmospheric Science Letters
DOI: 10.1002/asl.291
Tags: Cloud Brightening, Stratospheric Aerosols, Climate Modelling, Cloud Physics
URL: http://onlinelibrary.wiley.com/doi/10.1002/asl.291/abstract
Abstract: We examine the climate impact of geoengineering via two different methods, namely, stratospheric SO2 injection and increasing reflectivity of marine stratocumulus clouds. Although both methods appear capable, in principle, of counteracting the global mean warming due to increases in greenhouse gas concentrations, significant changes in regional climate still result. The extent of this regional climate change appears linked to the location and degree of inhomogeneity of the radiative flux perturbations produced by each geoengineering method.
Author(s): Jones A, Haywood J, Boucher O, Kravitz B, Robock A
Published: March, 2010
Publisher: Atmospheric Chemistry and Physics Discussions
DOI: 10.5194/acpd-10-7421-2010
Tags: Stratospheric Aerosols, Climate Modelling, Precipitation
URL: http://www.atmos-chem-phys-discuss.net/10/7421/2010/acpd-10-7421-2010.html
Abstract: We examine the response of the Met Office Hadley Centre's HadGEM2-AO climate model to simulated geoengineering by continuous injection of SO2 into the lower stratosphere, and compare the results with those from the Goddard Institute for Space Studies ModelE. The HadGEM2 simulations suggest that the SO2 injection rate considered here (5 Tg[SO2] yr−1) could defer the amount of global warming predicted under the Intergovernmental Panel on Climate Change's A1B scenario by approximately 30–35 years, although both models indicate rapid warming if geoengineering is not sustained. We find a broadly similar geographic distribution of the response to geoengineering in both models in terms of near-surface air temperature and mean June–August precipitation. The simulations also suggest that significant changes in regional climate would be experienced even if geoengineering was successful in maintaining global-mean temperature near current values.
Author(s): Jones A, Haywood J, Boucher O
Published: May, 2009
Publisher: Journal of Geophysical Research
DOI: 10.1029/2008JD011450
Tags: Environmental Side-Effects, Cloud Brightening, Climate Modelling, Precipitation, Cloud Physics
URL: http://www.agu.org/journals/ABS/2009/2008JD011450.shtml
Abstract: Theoretical potential geoengineering solutions to the global warming problem have recently been proposed. Here, we present an idealized study of the climate response to deliberately seeding large-scale stratocumulus cloud decks in the North Pacific, South Pacific, and South Atlantic, thereby inducing cooling via aerosol indirect effects. Atmosphere-only, atmosphere/mixed-layer ocean, and fully coupled atmosphere/ocean versions of the Met Office Hadley Centre model are used to investigate the radiative forcing, climate efficacy, and regional response of temperature, precipitation, and net primary productivity to such geoengineering. The radiative forcing simulations indicate that, for our parameterization of aerosol indirect effects, up to 35% of the radiative forcing due to current levels of greenhouse gases could be offset by stratocumulus modification. Equilibrium simulations with the atmosphere/mixed-layer ocean model, wherein each of the three stratocumulus sheets is modified in turn, reveal that the most efficient cooling per unit radiative forcing occurs when the South Pacific stratocumulus sheet is modified. Transient coupled model simulations suggest that geoengineering all three stratocumulus areas delays the simulated global warming by about 25 years. These simulations also indicate that, while some areas experience increases in precipitation and net primary productivity, sharp decreases are simulated in South America, with particularly detrimental impacts on the Amazon rain forest. These results show that, while some areas benefit from geoengineering, there are significant areas where the response could be very detrimental with implications for the practical applicability of such a scheme.
Author(s): Boucher O, Lowe JA, Jones CD
Published: October, 2008
Publisher: Climatic Change
DOI: 10.1007/s10584-008-9489-7
Tags: Stratospheric Aerosols, Climate Science
URL: http://www.springerlink.com/content/t64345806wmm57u1/
Abstract: Carbon dioxide emissions need to be reduced well below current emissions if atmospheric concentrations are to be stabilised at a level likely to avoid dangerous climate change. We investigate how delays in reducing CO2 emissions affect stabilisation scenarios leading to overshooting of a target concentration pathway. We show that if geo-engineering alone is used to compensate for the delay in reducing CO2 emissions, such an option needs to be sustained for centuries even though the period of overshooting emissions may only last for a few decades. If geo-engineering is used for a shorter period, it has to be associated with emission reductions significantly larger than those required to stabilise CO2 without overshooting the target. In the presence of a strong climate–carbon cycle feedback the required emission reductions are even more drastic.
Author(s): Woodhouse M, Mann G, Carslaw KS, Boucher O
Published: May, 2008
Publisher: Atmospheric Environment
DOI: 10.1016/j.atmosenv.2008.05.005
Tags: Cloud Brightening, Ocean Fertilization
URL: http://www.sciencedirect.com/science/article/pii/S1352231008004019
Abstract: Article on the impact emissions caused by iron fertilization in the Oceans, specifically emissions of aerosol particles that can act as cloud condensation nuclei.
Author(s): Dufresne JL, Quaas J, Boucher O, Denvil S, Fairhead L
Published: November, 2005
Publisher: Geophysical Research Letters
DOI: 10.1029/2005GL023619
Tags: Climate Science, Tropospheric Aerosols, Climate Modelling
URL: http://www.agu.org/journals/ABS/2005/2005GL023619.shtml
Abstract: In this study, we examine the time evolution of the relative contribution of sulfate aerosols and greenhouse gases to anthropogenic climate change. We use the new IPSL-CM4 coupled climate model for which the first indirect effect of sulfate aerosols has been calibrated using POLDER satellite data. For the recent historical period the sulfate aerosols play a key role on the temperature increase with a cooling effect of 0.5 K, to be compared to the 1.4 K warming due to greenhouse gas increase. In contrast, the projected temperature change for the 21st century is remarkably independent of the effects of anthropogenic sulfate aerosols for the SRES-A2 scenario. Those results are interpreted comparing the different radiative forcings, and can be extended to other scenarios. We also highlight that the first indirect effect of aerosol strongly depends on the land surface model by changing the cloud cover.
Showing results 1 - 10 of 10