K. Frieler - Academia.edu (original) (raw)
Papers by K. Frieler
IOP Conference Series: Earth and Environmental Science, 2009
This article was submitted without an abstract, please refer to the full-text PDF file.
Page 1. CHAPTER 4 Polar Ozone: Past and Present Contributors: GE Bodeker K. Frieler F. Goutail M.... more Page 1. CHAPTER 4 Polar Ozone: Past and Present Contributors: GE Bodeker K. Frieler F. Goutail M. López-Puertas GL Manney ER Nash CE Randall HJ Singer CS Singleton RM Stimpfle S. Tilmes M. Weber Lead Authors: PA Newman M. Rex ...
The chlorine chemistry under highly activated polar stratospheric spring conditions is critical t... more The chlorine chemistry under highly activated polar stratospheric spring conditions is critical to understanding the dramatic ozone losses that lead to the formation of the stratospheric ozone hole'. A particular flight pattern of the Geophysica high altitude aircraft during VINTERSOL-EUPLEX/SOLVE II on the 30th January 2003 in the Arctic was designed to test our theoretical understanding of the ClO/ClOOCl system. The outbound and inbound flight legs followed a calculated pattern such that the same air masses were sampled before and after sunset. During the inbound flight three encounters of the contrail from the outbound flight confirmed the success of the flight planning. In-situ ClO measurements were examined to study the conversion of ClO into its nighttime reservoir during sunset. Applying a trajectory Match technique, traditionally used to examine ozone-sonde concentrations, we examined this 3 hour period of ClO observations. 72 ClO Match pairs were identified with temperatures ranging between 200-206 K and SZAs between 84o and 95o. For a given Match pair the total active chlorine ClOx is assumed to be constant, but allowed to vary between Matches. This allowed the kinetic parameters controlling the ClO concentration - Keq, kf and J with differing SZA and temperatures to be closely examined. Due to the particular design of the flight pattern we are able to retrieve robust values for Keq based on ClO measurements alone. Hence our results for Keq are independent of the more uncertain dimer measurements (ClOOCl). We find values for Keq that are about a factor of 3-4 smaller than current JPL recommendations relatively independent of kf and J, as long as kf is larger than 70% of its recommended value. Derived values for J and ClOx are strongly anticorrelated. Hence, without dimer observations the retrieved J is very sensitive to assumptions about ClOx. However, using total available chlorine as an upper limit for ClOx, we find that the upper limits of the current JPL 2006 recommended range of uncertainty for J are required to explain the data of the self-Match fight. If measured values of ClOOCl are used to better constrain ClOx, even larger values of J are inferred. These results contrast with a recent laboratory measurement of the ClO dimer cross sections (Pope et al. 2007, J. Phys. Chem., in press), which leads to large differences between modeled and measured ClO. We shall explore additional chemical mechanisms that could account for observed ClO and ClOOCl during the self-Match flight, in light of the new laboratory cross section.
Utilizing in-situ measurements of ClO made in the same airmass more than once under different pho... more Utilizing in-situ measurements of ClO made in the same airmass more than once under different photochemical conditions during the Geophysica self-match flight during Euplex 2003, enabled us to examine our understanding of the kinetics of chlorine dimer cycle in detail. The kinetics of the chlorine dimer catalytic ozone loss cycle rely upon the thermal equilibrium between the monomer ClO and the dimer ClOOCl and the photolysis rate of the dimer ClOOCl. In this paper, we illustrate the kinetic constraints able to be determined by such a methodology. Our results suggest a thermal equilibrium constant a factor of 5 smaller and a ratio of photolysis rate to formation rate of ClOOCl a factor of 2 larger than the values based on the JPL recommendations.
Earth's Future, 2017
Key points • Process-based crop models forced by observational weather data can explain more than... more Key points • Process-based crop models forced by observational weather data can explain more than 50% of reported yield fluctuations in some major producing countries. • Water limitation seems to be major driver of the observed variations in most of these countries.
This paper has been accepted by PNAS as: "Multisectoral climate impact hotspots in a warming... more This paper has been accepted by PNAS as: "Multisectoral climate impact hotspots in a warming world."
Thawing of permafrost and the associated release of carbon constitutes a positive feedback in the... more Thawing of permafrost and the associated release of carbon constitutes a positive feedback in the climate system, elevating the effect of anthropogenic GHG emissions on global-mean temperatures. Multiple factors have hindered the quantification of this feedback, which was not included in the CMIP3 and C 4 MIP generation of AOGCMs and carbon cycle models. There are considerable uncertainties in the rate and extent of permafrost thaw, the hydrological and vegetation response to permafrost thaw, the decomposition timescales of freshly thawed organic material, the proportion of soil carbon that might be emitted as carbon dioxide via aerobic decomposition or as methane via anaerobic decomposition, and in the magnitude of the high latitude amplification of global warming that will drive permafrost degradation. Additionally, there are extensive and poorly characterized regional heterogeneities in soil properties, carbon content, and hydrology. Here, we couple a new permafrost module to a reduced complexity carbon-cycle climate model, which allows us to perform a large ensemble of simulations. The ensemble is designed to span the uncertainties listed above and thereby the results provide an estimate of the potential strength of the permafrost-carbon feedback. For the high CO 2 concentration scenario (RCP8.5), 12-52 PgC, or an extra 3-11% above projected net CO 2 emissions from land carbon cycle feedbacks, are released by 2100 (68% uncertainty range). This leads to an additional warming of 0.02-0.11°C. Though projected 21 st century emissions are relatively modest, ongoing permafrost thaw and slow but steady soil carbon decomposition means that, by 2300, more than half of the potentially vulnerable permafrost carbon stock in the upper 3m of soil layer (600-1000PgC) could be released as CO 2 , with an extra 1-3% being released as methane. Our results also suggest that mitigation action in line with the lower scenario RCP3-PD could contain Arctic temperature increase sufficiently that thawing of the permafrost area is limited to 15-30% and the permafrost-carbon induced temperature increase does not exceed 0.01-0.07°C by 2300.
Nature Communications, 2019
Global impact models represent process-level understanding of how natural and human systems may b... more Global impact models represent process-level understanding of how natural and human systems may be affected by climate change. Their projections are used in integrated assessments of climate change. Here we test, for the first time, systematically across many important systems, how well such impact models capture the impacts of extreme climate conditions. Using the 2003 European heat wave and drought as a historical analogue for comparable events in the future, we find that a majority of models underestimate the extremeness of impacts in important sectors such as agriculture, terrestrial ecosystems, and heat-related human mortality, while impacts on water resources and hydropower are overestimated in some river basins; and the spread across models is often large. This has important implications for economic assessments of climate change impacts that rely on these models. It also means that societal risks from future extreme events may be greater than previously thought.
SSRN Electronic Journal, 2016
World markets are highly interlinked and local economies extensively rely on global supply and va... more World markets are highly interlinked and local economies extensively rely on global supply and value chains. Consequently, local production disruptions, for instance caused by extreme weather events, are likely to induce indirect losses along supply chains with potentially global repercussions. These complex loss dynamics represent a challenge for comprehensive disaster risk assessments. Here, we introduce the numerical agentbased model acclimate designed to analyze the cascading of economic losses in the global supply network. Using national sectors as agents, we apply the model to study the global propagation of losses induced by stylized disasters. We find that indirect losses can become comparable in size to direct ones, but can be efficiently mitigated by warehousing and idle capacities. Consequently, a comprehensive risk assessment cannot focus solely on first-tier suppliers, but has to take the whole supply chain into account. To render the supply network climate-proof, national adaptation policies have to be complemented by international adaptation efforts. In that regard, our model can be employed to assess reasonable leverage points and to identify dynamic bottlenecks inaccessible to static analyses.
Nature communications, Jan 19, 2017
High temperatures are detrimental to crop yields and could lead to global warming-driven reductio... more High temperatures are detrimental to crop yields and could lead to global warming-driven reductions in agricultural productivity. To assess future threats, the majority of studies used process-based crop models, but their ability to represent effects of high temperature has been questioned. Here we show that an ensemble of nine crop models reproduces the observed average temperature responses of US maize, soybean and wheat yields. Each day >30 °C diminishes maize and soybean yields by up to 6% under rainfed conditions. Declines observed in irrigated areas, or simulated assuming full irrigation, are weak. This supports the hypothesis that water stress induced by high temperatures causes the decline. For wheat a negative response to high temperature is neither observed nor simulated under historical conditions, since critical temperatures are rarely exceeded during the growing season. In the future, yields are modelled to decline for all three crops at temperatures >30 °C. Eleva...
Earth System Dynamics, 2014
Despite significant progress in climate impact research, the narratives that science can presentl... more Despite significant progress in climate impact research, the narratives that science can presently piece together of a 2, 3, 4, or 5 • C warmer world remain fragmentary. Here we briefly review past undertakings to characterise comprehensively and quantify climate impacts based on multi-model approaches. We then report on the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP), a community-driven effort to compare impact models across sectors and scales systematically, and to quantify the uncertainties along the chain from greenhouse gas emissions and climate input data to the modelling of climate impacts themselves. We show how ISI-MIP and similar efforts can substantially advance the science relevant to impacts, adaptation and vulnerability, and we outline the steps that need to be taken in order to make the most of the available modelling tools. We discuss pertinent limitations of these methods and how they could be tackled. We argue that it is time to consolidate the current patchwork of impact knowledge through integrated cross-sectoral assessments, and that the climate impact community is now in a favourable position to do so.
Earth System Dynamics, 2014
The largest uncertainty in projections of future sea-level change results from the potentially ch... more The largest uncertainty in projections of future sea-level change results from the potentially changing dynamical ice discharge from Antarctica. Basal ice-shelf melting induced by a warming ocean has been identified as a major cause for additional ice flow across the grounding line. Here we attempt to estimate the uncertainty range of future ice discharge from Antarctica by combining uncertainty in the climatic forcing, the oceanic response and the ice-sheet model response. The uncertainty in the global mean temperature increase is obtained from historically constrained emulations with the MAGICC-6.0 (Model for the Assessment of Greenhouse gas Induced Climate Change) model. The oceanic forcing is derived from scaling of the subsurface with the atmospheric warming from 19 comprehensive climate models of the Coupled Model Intercomparison Project (CMIP-5) and two ocean models from the EU-project Ice2Sea. The dynamic ice-sheet response is derived from linear response functions for basal ice-shelf melting for four different Antarctic drainage regions using experiments from the Sea-level Response to Ice Sheet Evolution (SeaRISE) intercomparison project with five different Antarctic ice-sheet models. The resulting uncertainty range for the historic Antarctic contribution to global sealevel rise from 1992 to 2011 agrees with the observed contribution for this period if we use the three ice-sheet models with an explicit representation of ice-shelf dynamics and account for the time-delayed warming of the oceanic subsurface compared to the surface air temperature. The median of the additional ice loss for the 21st century is computed to 0.07 m (66 % range: 0.02-0.14 m; 90 % range: 0.0-0.23 m) of global sea-level equivalent for the low-emission RCP-2.6 (Representative Concentration Pathway) scenario and 0.09 m (66 % range: 0.04-0.21 m; 90 % range: 0.01-0.37 m) for the strongest RCP-8.5. Assuming no time delay between the atmospheric warming and the oceanic subsurface, these values increase to 0.09 m (66 % range: 0.04-0.17 m; 90 % range: 0.02-0.25 m) for RCP-2.6 and 0.15 m (66 % range: 0.07-0.28 m; 90 % range: 0.04-0.43 m) for RCP-8.5. All probability distributions are highly skewed towards high values. The applied ice-sheet models are coarse resolution with limitations in the representation of grounding-line motion. Within the constraints of the applied methods, the uncertainty induced from different ice-sheet models is smaller than that induced by the external forcing to the ice sheets.
Earth System Dynamics, 2013
Statistical bias correction is commonly applied within climate impact modelling to correct climat... more Statistical bias correction is commonly applied within climate impact modelling to correct climate model data for systematic deviations of the simulated historical data from observations. Methods are based on transfer functions generated to map the distribution of the simulated historical data to that of the observations. Those are subsequently applied to correct the future projections. Here, we present the bias correction method that was developed within ISI-MIP, the first Inter-Sectoral Impact Model Intercomparison Project. ISI-MIP is designed to synthesise impact projections in the agriculture, water, biome, health, and infrastructure sectors at different levels of global warming. Bias-corrected climate data that are used as input for the impact simulations could be only provided over land areas. To ensure consistency with the global (land + ocean) temperature information the bias correction method has to preserve the warming signal. Here we present the applied method that preserves the absolute changes in monthly temperature, and relative changes in monthly values of precipitation and the other variables needed for ISI-MIP. The proposed methodology represents a modification of the transfer function approach applied in the Water Model Intercomparison Project (Water-MIP). Correction of the monthly mean is followed by correction of the daily variability about the monthly mean. Besides the general idea and technical details of the ISI-MIP method, we show and discuss the potential and limitations of the applied bias correction. In particular, while the trend and the long-term mean are well represented, limitations with regards to the adjustment of the variability persist which may affect, e.g. small scale features or extremes.
Biogeosciences Discussions, 2011
Thawing of permafrost and the associated release of carbon constitutes a positive feedback in the... more Thawing of permafrost and the associated release of carbon constitutes a positive feedback in the climate system, elevating the effect of anthropogenic GHG emissions on global-mean temperatures. Multiple factors have hindered the quantification of this feedback, which was not included in the CMIP3 and C 4 MIP generation of AOGCMs and carbon cycle models. There are considerable uncertainties in the rate and extent of permafrost thaw, the hydrological and vegetation response to permafrost thaw, the decomposition timescales of freshly thawed organic material, the proportion of soil carbon that might be emitted as carbon dioxide via aerobic decomposition or as methane via anaerobic decomposition, and in the magnitude of the high latitude amplification of global warming that will drive permafrost degradation. Additionally, there are extensive and poorly characterized regional heterogeneities in soil properties, carbon content, and hydrology. Here, we couple a new permafrost module to a reduced complexity carbon-cycle climate model, which allows us to perform a large ensemble of simulations. The ensemble is designed to span the uncertainties listed above and thereby the results provide an estimate of the potential strength of the permafrost-carbon feedback. For the high CO 2 concentration scenario (RCP8.5), 12-52 PgC, or an extra 3-11 % above projected net CO 2 emissions from land carbon cycle feedbacks, are released by 2100 (68 % uncertainty range). This leads to an additional warming of 0.02-0.11 • C. Though projected 21st century emissions are relatively modest, ongoing permafrost thaw and slow but steady soil carbon decomposition means that, by 2300, more than half of the potentially vulnerable permafrost carbon stock in the upper 3m of soil layer (600-1000 PgC) could be released as CO 2 , with an extra 1-3 % being released as methane. Our results also suggest that mitigation action in line with the lower scenario RCP3-PD could contain Arctic temperature increase sufficiently that thawing of the permafrost area is limited to 15-30 % and the permafrost-carbon induced temperature increase does not exceed 0.01-0.
IOP Conference Series: Earth and Environmental Science, 2009
This article was submitted without an abstract, please refer to the full-text PDF file.
Page 1. CHAPTER 4 Polar Ozone: Past and Present Contributors: GE Bodeker K. Frieler F. Goutail M.... more Page 1. CHAPTER 4 Polar Ozone: Past and Present Contributors: GE Bodeker K. Frieler F. Goutail M. López-Puertas GL Manney ER Nash CE Randall HJ Singer CS Singleton RM Stimpfle S. Tilmes M. Weber Lead Authors: PA Newman M. Rex ...
The chlorine chemistry under highly activated polar stratospheric spring conditions is critical t... more The chlorine chemistry under highly activated polar stratospheric spring conditions is critical to understanding the dramatic ozone losses that lead to the formation of the stratospheric ozone hole'. A particular flight pattern of the Geophysica high altitude aircraft during VINTERSOL-EUPLEX/SOLVE II on the 30th January 2003 in the Arctic was designed to test our theoretical understanding of the ClO/ClOOCl system. The outbound and inbound flight legs followed a calculated pattern such that the same air masses were sampled before and after sunset. During the inbound flight three encounters of the contrail from the outbound flight confirmed the success of the flight planning. In-situ ClO measurements were examined to study the conversion of ClO into its nighttime reservoir during sunset. Applying a trajectory Match technique, traditionally used to examine ozone-sonde concentrations, we examined this 3 hour period of ClO observations. 72 ClO Match pairs were identified with temperatures ranging between 200-206 K and SZAs between 84o and 95o. For a given Match pair the total active chlorine ClOx is assumed to be constant, but allowed to vary between Matches. This allowed the kinetic parameters controlling the ClO concentration - Keq, kf and J with differing SZA and temperatures to be closely examined. Due to the particular design of the flight pattern we are able to retrieve robust values for Keq based on ClO measurements alone. Hence our results for Keq are independent of the more uncertain dimer measurements (ClOOCl). We find values for Keq that are about a factor of 3-4 smaller than current JPL recommendations relatively independent of kf and J, as long as kf is larger than 70% of its recommended value. Derived values for J and ClOx are strongly anticorrelated. Hence, without dimer observations the retrieved J is very sensitive to assumptions about ClOx. However, using total available chlorine as an upper limit for ClOx, we find that the upper limits of the current JPL 2006 recommended range of uncertainty for J are required to explain the data of the self-Match fight. If measured values of ClOOCl are used to better constrain ClOx, even larger values of J are inferred. These results contrast with a recent laboratory measurement of the ClO dimer cross sections (Pope et al. 2007, J. Phys. Chem., in press), which leads to large differences between modeled and measured ClO. We shall explore additional chemical mechanisms that could account for observed ClO and ClOOCl during the self-Match flight, in light of the new laboratory cross section.
Utilizing in-situ measurements of ClO made in the same airmass more than once under different pho... more Utilizing in-situ measurements of ClO made in the same airmass more than once under different photochemical conditions during the Geophysica self-match flight during Euplex 2003, enabled us to examine our understanding of the kinetics of chlorine dimer cycle in detail. The kinetics of the chlorine dimer catalytic ozone loss cycle rely upon the thermal equilibrium between the monomer ClO and the dimer ClOOCl and the photolysis rate of the dimer ClOOCl. In this paper, we illustrate the kinetic constraints able to be determined by such a methodology. Our results suggest a thermal equilibrium constant a factor of 5 smaller and a ratio of photolysis rate to formation rate of ClOOCl a factor of 2 larger than the values based on the JPL recommendations.
Earth's Future, 2017
Key points • Process-based crop models forced by observational weather data can explain more than... more Key points • Process-based crop models forced by observational weather data can explain more than 50% of reported yield fluctuations in some major producing countries. • Water limitation seems to be major driver of the observed variations in most of these countries.
This paper has been accepted by PNAS as: "Multisectoral climate impact hotspots in a warming... more This paper has been accepted by PNAS as: "Multisectoral climate impact hotspots in a warming world."
Thawing of permafrost and the associated release of carbon constitutes a positive feedback in the... more Thawing of permafrost and the associated release of carbon constitutes a positive feedback in the climate system, elevating the effect of anthropogenic GHG emissions on global-mean temperatures. Multiple factors have hindered the quantification of this feedback, which was not included in the CMIP3 and C 4 MIP generation of AOGCMs and carbon cycle models. There are considerable uncertainties in the rate and extent of permafrost thaw, the hydrological and vegetation response to permafrost thaw, the decomposition timescales of freshly thawed organic material, the proportion of soil carbon that might be emitted as carbon dioxide via aerobic decomposition or as methane via anaerobic decomposition, and in the magnitude of the high latitude amplification of global warming that will drive permafrost degradation. Additionally, there are extensive and poorly characterized regional heterogeneities in soil properties, carbon content, and hydrology. Here, we couple a new permafrost module to a reduced complexity carbon-cycle climate model, which allows us to perform a large ensemble of simulations. The ensemble is designed to span the uncertainties listed above and thereby the results provide an estimate of the potential strength of the permafrost-carbon feedback. For the high CO 2 concentration scenario (RCP8.5), 12-52 PgC, or an extra 3-11% above projected net CO 2 emissions from land carbon cycle feedbacks, are released by 2100 (68% uncertainty range). This leads to an additional warming of 0.02-0.11°C. Though projected 21 st century emissions are relatively modest, ongoing permafrost thaw and slow but steady soil carbon decomposition means that, by 2300, more than half of the potentially vulnerable permafrost carbon stock in the upper 3m of soil layer (600-1000PgC) could be released as CO 2 , with an extra 1-3% being released as methane. Our results also suggest that mitigation action in line with the lower scenario RCP3-PD could contain Arctic temperature increase sufficiently that thawing of the permafrost area is limited to 15-30% and the permafrost-carbon induced temperature increase does not exceed 0.01-0.07°C by 2300.
Nature Communications, 2019
Global impact models represent process-level understanding of how natural and human systems may b... more Global impact models represent process-level understanding of how natural and human systems may be affected by climate change. Their projections are used in integrated assessments of climate change. Here we test, for the first time, systematically across many important systems, how well such impact models capture the impacts of extreme climate conditions. Using the 2003 European heat wave and drought as a historical analogue for comparable events in the future, we find that a majority of models underestimate the extremeness of impacts in important sectors such as agriculture, terrestrial ecosystems, and heat-related human mortality, while impacts on water resources and hydropower are overestimated in some river basins; and the spread across models is often large. This has important implications for economic assessments of climate change impacts that rely on these models. It also means that societal risks from future extreme events may be greater than previously thought.
SSRN Electronic Journal, 2016
World markets are highly interlinked and local economies extensively rely on global supply and va... more World markets are highly interlinked and local economies extensively rely on global supply and value chains. Consequently, local production disruptions, for instance caused by extreme weather events, are likely to induce indirect losses along supply chains with potentially global repercussions. These complex loss dynamics represent a challenge for comprehensive disaster risk assessments. Here, we introduce the numerical agentbased model acclimate designed to analyze the cascading of economic losses in the global supply network. Using national sectors as agents, we apply the model to study the global propagation of losses induced by stylized disasters. We find that indirect losses can become comparable in size to direct ones, but can be efficiently mitigated by warehousing and idle capacities. Consequently, a comprehensive risk assessment cannot focus solely on first-tier suppliers, but has to take the whole supply chain into account. To render the supply network climate-proof, national adaptation policies have to be complemented by international adaptation efforts. In that regard, our model can be employed to assess reasonable leverage points and to identify dynamic bottlenecks inaccessible to static analyses.
Nature communications, Jan 19, 2017
High temperatures are detrimental to crop yields and could lead to global warming-driven reductio... more High temperatures are detrimental to crop yields and could lead to global warming-driven reductions in agricultural productivity. To assess future threats, the majority of studies used process-based crop models, but their ability to represent effects of high temperature has been questioned. Here we show that an ensemble of nine crop models reproduces the observed average temperature responses of US maize, soybean and wheat yields. Each day >30 °C diminishes maize and soybean yields by up to 6% under rainfed conditions. Declines observed in irrigated areas, or simulated assuming full irrigation, are weak. This supports the hypothesis that water stress induced by high temperatures causes the decline. For wheat a negative response to high temperature is neither observed nor simulated under historical conditions, since critical temperatures are rarely exceeded during the growing season. In the future, yields are modelled to decline for all three crops at temperatures >30 °C. Eleva...
Earth System Dynamics, 2014
Despite significant progress in climate impact research, the narratives that science can presentl... more Despite significant progress in climate impact research, the narratives that science can presently piece together of a 2, 3, 4, or 5 • C warmer world remain fragmentary. Here we briefly review past undertakings to characterise comprehensively and quantify climate impacts based on multi-model approaches. We then report on the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP), a community-driven effort to compare impact models across sectors and scales systematically, and to quantify the uncertainties along the chain from greenhouse gas emissions and climate input data to the modelling of climate impacts themselves. We show how ISI-MIP and similar efforts can substantially advance the science relevant to impacts, adaptation and vulnerability, and we outline the steps that need to be taken in order to make the most of the available modelling tools. We discuss pertinent limitations of these methods and how they could be tackled. We argue that it is time to consolidate the current patchwork of impact knowledge through integrated cross-sectoral assessments, and that the climate impact community is now in a favourable position to do so.
Earth System Dynamics, 2014
The largest uncertainty in projections of future sea-level change results from the potentially ch... more The largest uncertainty in projections of future sea-level change results from the potentially changing dynamical ice discharge from Antarctica. Basal ice-shelf melting induced by a warming ocean has been identified as a major cause for additional ice flow across the grounding line. Here we attempt to estimate the uncertainty range of future ice discharge from Antarctica by combining uncertainty in the climatic forcing, the oceanic response and the ice-sheet model response. The uncertainty in the global mean temperature increase is obtained from historically constrained emulations with the MAGICC-6.0 (Model for the Assessment of Greenhouse gas Induced Climate Change) model. The oceanic forcing is derived from scaling of the subsurface with the atmospheric warming from 19 comprehensive climate models of the Coupled Model Intercomparison Project (CMIP-5) and two ocean models from the EU-project Ice2Sea. The dynamic ice-sheet response is derived from linear response functions for basal ice-shelf melting for four different Antarctic drainage regions using experiments from the Sea-level Response to Ice Sheet Evolution (SeaRISE) intercomparison project with five different Antarctic ice-sheet models. The resulting uncertainty range for the historic Antarctic contribution to global sealevel rise from 1992 to 2011 agrees with the observed contribution for this period if we use the three ice-sheet models with an explicit representation of ice-shelf dynamics and account for the time-delayed warming of the oceanic subsurface compared to the surface air temperature. The median of the additional ice loss for the 21st century is computed to 0.07 m (66 % range: 0.02-0.14 m; 90 % range: 0.0-0.23 m) of global sea-level equivalent for the low-emission RCP-2.6 (Representative Concentration Pathway) scenario and 0.09 m (66 % range: 0.04-0.21 m; 90 % range: 0.01-0.37 m) for the strongest RCP-8.5. Assuming no time delay between the atmospheric warming and the oceanic subsurface, these values increase to 0.09 m (66 % range: 0.04-0.17 m; 90 % range: 0.02-0.25 m) for RCP-2.6 and 0.15 m (66 % range: 0.07-0.28 m; 90 % range: 0.04-0.43 m) for RCP-8.5. All probability distributions are highly skewed towards high values. The applied ice-sheet models are coarse resolution with limitations in the representation of grounding-line motion. Within the constraints of the applied methods, the uncertainty induced from different ice-sheet models is smaller than that induced by the external forcing to the ice sheets.
Earth System Dynamics, 2013
Statistical bias correction is commonly applied within climate impact modelling to correct climat... more Statistical bias correction is commonly applied within climate impact modelling to correct climate model data for systematic deviations of the simulated historical data from observations. Methods are based on transfer functions generated to map the distribution of the simulated historical data to that of the observations. Those are subsequently applied to correct the future projections. Here, we present the bias correction method that was developed within ISI-MIP, the first Inter-Sectoral Impact Model Intercomparison Project. ISI-MIP is designed to synthesise impact projections in the agriculture, water, biome, health, and infrastructure sectors at different levels of global warming. Bias-corrected climate data that are used as input for the impact simulations could be only provided over land areas. To ensure consistency with the global (land + ocean) temperature information the bias correction method has to preserve the warming signal. Here we present the applied method that preserves the absolute changes in monthly temperature, and relative changes in monthly values of precipitation and the other variables needed for ISI-MIP. The proposed methodology represents a modification of the transfer function approach applied in the Water Model Intercomparison Project (Water-MIP). Correction of the monthly mean is followed by correction of the daily variability about the monthly mean. Besides the general idea and technical details of the ISI-MIP method, we show and discuss the potential and limitations of the applied bias correction. In particular, while the trend and the long-term mean are well represented, limitations with regards to the adjustment of the variability persist which may affect, e.g. small scale features or extremes.
Biogeosciences Discussions, 2011
Thawing of permafrost and the associated release of carbon constitutes a positive feedback in the... more Thawing of permafrost and the associated release of carbon constitutes a positive feedback in the climate system, elevating the effect of anthropogenic GHG emissions on global-mean temperatures. Multiple factors have hindered the quantification of this feedback, which was not included in the CMIP3 and C 4 MIP generation of AOGCMs and carbon cycle models. There are considerable uncertainties in the rate and extent of permafrost thaw, the hydrological and vegetation response to permafrost thaw, the decomposition timescales of freshly thawed organic material, the proportion of soil carbon that might be emitted as carbon dioxide via aerobic decomposition or as methane via anaerobic decomposition, and in the magnitude of the high latitude amplification of global warming that will drive permafrost degradation. Additionally, there are extensive and poorly characterized regional heterogeneities in soil properties, carbon content, and hydrology. Here, we couple a new permafrost module to a reduced complexity carbon-cycle climate model, which allows us to perform a large ensemble of simulations. The ensemble is designed to span the uncertainties listed above and thereby the results provide an estimate of the potential strength of the permafrost-carbon feedback. For the high CO 2 concentration scenario (RCP8.5), 12-52 PgC, or an extra 3-11 % above projected net CO 2 emissions from land carbon cycle feedbacks, are released by 2100 (68 % uncertainty range). This leads to an additional warming of 0.02-0.11 • C. Though projected 21st century emissions are relatively modest, ongoing permafrost thaw and slow but steady soil carbon decomposition means that, by 2300, more than half of the potentially vulnerable permafrost carbon stock in the upper 3m of soil layer (600-1000 PgC) could be released as CO 2 , with an extra 1-3 % being released as methane. Our results also suggest that mitigation action in line with the lower scenario RCP3-PD could contain Arctic temperature increase sufficiently that thawing of the permafrost area is limited to 15-30 % and the permafrost-carbon induced temperature increase does not exceed 0.01-0.