This thesis presents the initial results from climateprediction.net’s paleo-experiments. A grand ... more This thesis presents the initial results from climateprediction.net’s paleo-experiments. A grand ensemble of paleo-climate models was successfully designed and executed using this distributed computing approach. The physical parameters, initial conditions and boundary conditions were perturbed in two sets of experiments distributed to the general public. The paleo - focus period is the mid-Holocene, i.e. �6000 years before present (6kyBP), due to its relative climatic stability and the abundance of geological evidence. Attempting to simulate climates that were substantially different from today provides an opportunity to evaluate model skill. A set of robust 6kyBP climatological features were established to benchmark the climate model against in order to assess the model’s abilities. Two experiments were distributed: in the first experiment the boundary conditions in the 6kyBP models took on the standard Paleoclimate Modelling Intercomparison Project (PMIP) values with altered orbit...
As a potential approach to prevent dangerous climate change, stratospheric aerosol geoengineering... more As a potential approach to prevent dangerous climate change, stratospheric aerosol geoengineering (SAG) aims to reflect some incoming solar radiation into space and reduce temperatures. Previous modeling studies suggest that storm tracks will shift poleward due to the increases in the greenhouse gas concentrations. As a consequence of this, the Middle East, North Africa, and Mediterranean regions will most likely experience a strong precipitation decrease, increasing the pressure on the region's vulnerable environment. Our results from an Earth system model indicate that SAG can partially offset the poleward shift of the storm tracks, thus potentially soothing the environmental and water stresses of the region. However, other climatic side effects may occur, hence still motivating ambitious mitigation action to reduce emissions and impacts of global warming. The results presented may have practical implications for ongoing climate policy debates in the region.
Climate engineering arises as one of the potential methods that could contribute to meeting the 1... more Climate engineering arises as one of the potential methods that could contribute to meeting the 1.5 °C global warming target agreed under the Paris Agreement. We examine how permafrost and high‐latitude vegetation respond to the large‐scale implementation of climate engineering. Specifically, we explore the impacts of applying the solar radiation management method of stratospheric aerosol injections (SAI) on permafrost temperature and the global extent of near‐surface permafrost area. We compare the RCP8.5 and RCP4.5 scenarios to several SAI deployment scenarios using the Norwegian Earth System Model (CE1 = moderate SAI scenario to bring down the global mean warming in RCP8.5 to the RCP4.5 level, CE2 = aggresive SAI scenario to maintain the global mean temperature toward the preindustrial level). We show that large‐scale application of SAI may help slow down the current rate of permafrost degradation for a wide range of emission scenarios. Between the RCP4.5 and CE1 simulations, the...
Current mitigation efforts and existing future commitments are inadequate to accomplish the Paris... more Current mitigation efforts and existing future commitments are inadequate to accomplish the Paris Agreement temperature goals. In light of this, research and debate are intensifying on the possibilities of additionally employing proposed climate geoengineering technologies, either through atmospheric carbon dioxide removal or farther-reaching interventions altering the Earth’s radiative energy budget. Although research indicates that several techniques may eventually have the physical potential to contribute to limiting climate change, all are in early stages of development, involve substantial uncertainties and risks, and raise ethical and governance dilemmas. Based on present knowledge, climate geoengineering techniques cannot be relied on to significantly contribute to meeting the Paris Agreement temperature goals.
Despite a growing literature on the climate response to solar geoengineering—proposals to cool th... more Despite a growing literature on the climate response to solar geoengineering—proposals to cool the planet by increasing the planetary albedo—there has been little published on the impacts of solar geoengineering on natural and human systems such as agriculture, health, water resources, and ecosystems. An understanding of the impacts of different scenarios of solar geoengineering deployment will be crucial for informing decisions on whether and how to deploy it. Here we review the current state of knowledge about impacts of a solar‐geoengineered climate and identify the major research gaps. We suggest that a thorough assessment of the climate impacts of a range of scenarios of solar geoengineering deployment is needed and can be built upon existing frameworks. However, solar geoengineering poses a novel challenge for climate impacts research as the manner of deployment could be tailored to pursue different objectives making possible a wide range of climate outcomes. We present a numb...
Atmospheric Chemistry and Physics Discussions, 2017
Marine cloud brightening through sea spray injection has been proposed as a climate engineering m... more Marine cloud brightening through sea spray injection has been proposed as a climate engineering method for avoiding the most severe consequences of global warming. A limitation of most of the previous modelling studies on marine cloud brightening is that they have either considered individual models, or only investigated the effects of a specific increase in the number of cloud droplets. Here we present results from coordinated simulations with three Earth system models (ESMs) participating in the Geoengineering Model Intercomparison Project (GeoMIP) G4sea-salt experiment. Injection rates of accumulation mode sea spray aerosol particles over ocean between 30° N and 30° S are set in each model to generate a global-mean effective radiative forcing (ERF) of −2.0 W m<sup>−2</sup> at the top of atmosphere. We find that the injection increases the cloud droplet number concentration in lower layers, reduces the cloud-top effective droplet radius, and increases the c...
Here we use an Earth System Model with interactive biogeochemistry to project future ocean biogeo... more Here we use an Earth System Model with interactive biogeochemistry to project future ocean biogeochemistry impacts from large-scale deployment of three different radiation management (RM) climate engineering (also known as geoengineering) methods: stratospheric aerosol injection (SAI), marine sky brightening (MSB), and cirrus cloud thinning (CCT). We apply RM such that the change in radiative forcing in the RCP8.5 emission scenario is reduced to the change in radiative forcing in the RCP4.5 scenario. The resulting global mean sea surface temperatures in the RM experiments are comparable to those in RCP4.5, but there are regional differences. The forcing from MSB, for example, is applied over the oceans, so the cooling of the ocean is in some regions stronger for this method of RM than for the others. Changes in ocean primary production are much more variable, but SAI and MSB give a global decrease comparable to RCP4.5 (~ 6 % in 2100 relative to 1971–2000), while ...
This thesis presents the initial results from climateprediction.net’s paleo-experiments. A grand ... more This thesis presents the initial results from climateprediction.net’s paleo-experiments. A grand ensemble of paleo-climate models was successfully designed and executed using this distributed computing approach. The physical parameters, initial conditions and boundary conditions were perturbed in two sets of experiments distributed to the general public. The paleo - focus period is the mid-Holocene, i.e. �6000 years before present (6kyBP), due to its relative climatic stability and the abundance of geological evidence. Attempting to simulate climates that were substantially different from today provides an opportunity to evaluate model skill. A set of robust 6kyBP climatological features were established to benchmark the climate model against in order to assess the model’s abilities. Two experiments were distributed: in the first experiment the boundary conditions in the 6kyBP models took on the standard Paleoclimate Modelling Intercomparison Project (PMIP) values with altered orbit...
As a potential approach to prevent dangerous climate change, stratospheric aerosol geoengineering... more As a potential approach to prevent dangerous climate change, stratospheric aerosol geoengineering (SAG) aims to reflect some incoming solar radiation into space and reduce temperatures. Previous modeling studies suggest that storm tracks will shift poleward due to the increases in the greenhouse gas concentrations. As a consequence of this, the Middle East, North Africa, and Mediterranean regions will most likely experience a strong precipitation decrease, increasing the pressure on the region's vulnerable environment. Our results from an Earth system model indicate that SAG can partially offset the poleward shift of the storm tracks, thus potentially soothing the environmental and water stresses of the region. However, other climatic side effects may occur, hence still motivating ambitious mitigation action to reduce emissions and impacts of global warming. The results presented may have practical implications for ongoing climate policy debates in the region.
Climate engineering arises as one of the potential methods that could contribute to meeting the 1... more Climate engineering arises as one of the potential methods that could contribute to meeting the 1.5 °C global warming target agreed under the Paris Agreement. We examine how permafrost and high‐latitude vegetation respond to the large‐scale implementation of climate engineering. Specifically, we explore the impacts of applying the solar radiation management method of stratospheric aerosol injections (SAI) on permafrost temperature and the global extent of near‐surface permafrost area. We compare the RCP8.5 and RCP4.5 scenarios to several SAI deployment scenarios using the Norwegian Earth System Model (CE1 = moderate SAI scenario to bring down the global mean warming in RCP8.5 to the RCP4.5 level, CE2 = aggresive SAI scenario to maintain the global mean temperature toward the preindustrial level). We show that large‐scale application of SAI may help slow down the current rate of permafrost degradation for a wide range of emission scenarios. Between the RCP4.5 and CE1 simulations, the...
Current mitigation efforts and existing future commitments are inadequate to accomplish the Paris... more Current mitigation efforts and existing future commitments are inadequate to accomplish the Paris Agreement temperature goals. In light of this, research and debate are intensifying on the possibilities of additionally employing proposed climate geoengineering technologies, either through atmospheric carbon dioxide removal or farther-reaching interventions altering the Earth’s radiative energy budget. Although research indicates that several techniques may eventually have the physical potential to contribute to limiting climate change, all are in early stages of development, involve substantial uncertainties and risks, and raise ethical and governance dilemmas. Based on present knowledge, climate geoengineering techniques cannot be relied on to significantly contribute to meeting the Paris Agreement temperature goals.
Despite a growing literature on the climate response to solar geoengineering—proposals to cool th... more Despite a growing literature on the climate response to solar geoengineering—proposals to cool the planet by increasing the planetary albedo—there has been little published on the impacts of solar geoengineering on natural and human systems such as agriculture, health, water resources, and ecosystems. An understanding of the impacts of different scenarios of solar geoengineering deployment will be crucial for informing decisions on whether and how to deploy it. Here we review the current state of knowledge about impacts of a solar‐geoengineered climate and identify the major research gaps. We suggest that a thorough assessment of the climate impacts of a range of scenarios of solar geoengineering deployment is needed and can be built upon existing frameworks. However, solar geoengineering poses a novel challenge for climate impacts research as the manner of deployment could be tailored to pursue different objectives making possible a wide range of climate outcomes. We present a numb...
Atmospheric Chemistry and Physics Discussions, 2017
Marine cloud brightening through sea spray injection has been proposed as a climate engineering m... more Marine cloud brightening through sea spray injection has been proposed as a climate engineering method for avoiding the most severe consequences of global warming. A limitation of most of the previous modelling studies on marine cloud brightening is that they have either considered individual models, or only investigated the effects of a specific increase in the number of cloud droplets. Here we present results from coordinated simulations with three Earth system models (ESMs) participating in the Geoengineering Model Intercomparison Project (GeoMIP) G4sea-salt experiment. Injection rates of accumulation mode sea spray aerosol particles over ocean between 30° N and 30° S are set in each model to generate a global-mean effective radiative forcing (ERF) of −2.0 W m<sup>−2</sup> at the top of atmosphere. We find that the injection increases the cloud droplet number concentration in lower layers, reduces the cloud-top effective droplet radius, and increases the c...
Here we use an Earth System Model with interactive biogeochemistry to project future ocean biogeo... more Here we use an Earth System Model with interactive biogeochemistry to project future ocean biogeochemistry impacts from large-scale deployment of three different radiation management (RM) climate engineering (also known as geoengineering) methods: stratospheric aerosol injection (SAI), marine sky brightening (MSB), and cirrus cloud thinning (CCT). We apply RM such that the change in radiative forcing in the RCP8.5 emission scenario is reduced to the change in radiative forcing in the RCP4.5 scenario. The resulting global mean sea surface temperatures in the RM experiments are comparable to those in RCP4.5, but there are regional differences. The forcing from MSB, for example, is applied over the oceans, so the cooling of the ocean is in some regions stronger for this method of RM than for the others. Changes in ocean primary production are much more variable, but SAI and MSB give a global decrease comparable to RCP4.5 (~ 6 % in 2100 relative to 1971–2000), while ...
Geological evidence indicate that the mid-Holocene experienced stronger than present day monsoon ... more Geological evidence indicate that the mid-Holocene experienced stronger than present day monsoon circulations, particularly across northern Africa. Sahara saw more in the way of a Sahelian vegetation, rather than the present day hyper arid conditions. General Circulation Models notoriously underestimate the northwards expansion of the increase in the Saharan moisture budget at 6kyBP. Here results are presented from a model (HadSM3) run in which the vegetation has been altered across northern Africa and the Middle East to evaluate the vegetation -- climate feedbacks. In addition to altering the orbital boundary conditions to 6k settings, the vegetation is changed from desert to rain forest, as opposed to a more realistic 6kyBP vegetation cover of steppe. This is to tease out a stronger signal and see if the modelled climate can be kicked out of its regional dry regime.
Results will be presented from Earth System Model simulations of the climate engineering method o... more Results will be presented from Earth System Model simulations of the climate engineering method of cirrus cloud thinning. This climate engineering method aims to cool temperatures as a response to seeding of high altitude ice clouds in order to deplete them. Hence more longwave radiation is allowed to escape to space. The ice crystal fall speed is perturbed as a simplified representation of the otherwise complex and computationally expensive micro- physics of the method. An octupling of the ice crystal fall speed at temperatures colder than 235K is found to be of the order of magnitude needed to offset the radiative forcing of a doubling of pre-industrial CO2 concentrations. The resulting climatic effects are presented, including the response of temperatures, hydrological cycle, with a particular emphasis on the East Asian Summer Monsoon.
Attempting to simulate climates substantially different from today offers an opportunity not only... more Attempting to simulate climates substantially different from today offers an opportunity not only to evaluate model skill but also a chance to test our understanding of the fundamental mechanisms governing our climate. The importance of the role played by boundary conditions in GCMs, in particular land ice, are explored in this study. The period of focus is the mid-Holocene, i.e. ∼6000 years before present (6kyBP), when the climate was stable and the forcing on the climate well known. To date the General Circulation Models (GCMs) have struggled to simulate the regional climate of Eastern North America correctly. This is attempted to be rectified with this experiment where new and improved local boundary conditions are implemented in an ensemble of paleo-climate models. The remnants of the Laurentide ice sheet is included and the Hudson Bay is somewhat expanded in the model. The ensemble results are compared to geological evidence from the region. The Eastern North American boundary condition experiment concludes that the perturbations brought the climate models to a closer agreement with the geological records regionally.
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Papers by Helene Muri
thinning. This climate engineering method aims to cool temperatures as a response to seeding of high altitude ice
clouds in order to deplete them. Hence more longwave radiation is allowed to escape to space. The ice crystal fall
speed is perturbed as a simplified representation of the otherwise complex and computationally expensive micro-
physics of the method. An octupling of the ice crystal fall speed at temperatures colder than 235K is found to be
of the order of magnitude needed to offset the radiative forcing of a doubling of pre-industrial CO2
concentrations.
The resulting climatic effects are presented, including the response of temperatures, hydrological cycle, with a
particular emphasis on the East Asian Summer Monsoon.