scholarly journals Thermodynamic and dynamic responses of the hydrological cycle to solar dimming

2016 ◽  
Author(s):  
Jane E. Smyth ◽  
Rick D. Russotto ◽  
Trude Storelvmo
Keyword(s):  
Hydrological Cycle ◽  
Global Climate ◽  
Hadley Circulation ◽  
Climate Impacts ◽  
Dynamic Responses ◽  
Tropical Precipitation ◽  
Solar Geoengineering ◽  
Intercomparison Project ◽  
Rainfall Anomalies ◽  
Precipitation Changes

Abstract. The fundamental role of the hydrological cycle in the global climate system motivates thorough evaluation of its responses to climate change and mitigation. The Geoengineering Model Intercomparison Project (GeoMIP) is a global collaboration that aims to assess the climate impacts of solar geoengineering, a proposal to counteract global warming with a reduction of incoming solar radiation. We assess the mechanisms underlying the rainfall response to a simplified simulation of solar dimming in the suite of GeoMIP models and identify robust features. While solar geoengineering restores preindustrial temperatures, the global hydrology is altered. Tropical precipitation changes dominate the response across the model suite. The models indicate a range of possibilities for the hydrological response, and in most cases, both thermodynamic and non-thermodynamic mechanisms drive precipitation minus evaporation changes in the geoengineered simulations relative to the preindustrial. Shifts of the Hadley circulation cells cause greater rainfall anomalies than local changes in relative humidity or the Clausius-Clapeyron scaling of precipitation minus evaporation. The variations among models in the movement of the intertropical convergence zone highlights the need for cautious consideration and continued study before any implementation of solar geoengineering.

scholarly journals Thermodynamic and dynamic responses of the hydrological cycle to solar dimming

2017 ◽  
Vol 17 (10) ◽  
pp. 6439-6453 ◽  
Author(s):  
Jane E. Smyth ◽  
Rick D. Russotto ◽  
Trude Storelvmo
Keyword(s):  
Relative Humidity ◽  
Hydrological Cycle ◽  
Global Climate ◽  
Hadley Circulation ◽  
Climate Impacts ◽  
Seasonal Migration ◽  
Dynamic Responses ◽  
Summer Hemisphere ◽  
Solar Geoengineering ◽  
Precipitation Changes

Abstract. The fundamental role of the hydrological cycle in the global climate system motivates a thorough evaluation of its responses to climate change and mitigation. The Geoengineering Model Intercomparison Project (GeoMIP) is a coordinated international effort to assess the climate impacts of solar geoengineering, a proposal to counteract global warming with a reduction in incoming solar radiation. We assess the mechanisms underlying the rainfall response to a simplified simulation of such solar dimming (G1) in the suite of GeoMIP models and identify robust features. While solar geoengineering nearly restores preindustrial temperatures, the global hydrology is altered. Tropical precipitation changes dominate the response across the model suite, and these are driven primarily by shifts of the Hadley circulation cells. We report a damping of the seasonal migration of the Intertropical Convergence Zone (ITCZ) in G1, associated with preferential cooling of the summer hemisphere, and annual mean ITCZ shifts in some models that are correlated with the warming of one hemisphere relative to the other. Dynamical changes better explain the varying tropical rainfall anomalies between models than changes in relative humidity or the Clausius–Clapeyron scaling of precipitation minus evaporation (P − E), given that the relative humidity and temperature responses are robust across the suite. Strong reductions in relative humidity over vegetated land regions are likely related to the CO2 physiological response in plants. The uncertainty in the spatial distribution of tropical P − E changes highlights the need for cautious consideration and continued study before any implementation of solar geoengineering.

Steering and Influence in Transnational Climate Governance: Nonstate Engagement in Solar Geoengineering Research

2020 ◽  
Vol 20 (3) ◽  
pp. 93-111
Author(s):  
Joshua B. Horton ◽  
Barbara Koremenos
Keyword(s):  
Global Climate ◽  
Climate Impacts ◽  
Transnational Governance ◽  
Climate Governance ◽  
Climate Risks ◽  
Novel Technology ◽  
Transnational Actors ◽  
Solar Geoengineering ◽  
Effective Policy ◽  
Transnational Climate Governance

Theorists of transnational climate governance (TCG) seek to account for the increasing involvement of nonstate and substate actors in global climate policy. While transnational actors have been present in the emerging field of solar geoengineering—a novel technology intended to reflect a fraction of sunlight back to space to reduce climate impacts—many of their most significant activities, including knowledge dissemination, scientific capacity building, and conventional lobbying, are not captured by the TCG framework. Insofar as TCG is identified with transnational governance and transnational governance is important to reducing climate risks, an incomplete TCG framework is problematic for effective policy making. We attribute this shortcoming on the part of TCG to its exclusive focus on steering and corollary exclusion of influence as a critical component of governance. Exercising influence, for example, through inside and outside lobbying, is an important part of transnational governance—it complements direct governing with indirect efforts to inform, persuade, pressure, or otherwise influence both governor and governed. Based on an empirical analysis of solar geoengineering research governance and a theoretical consideration of alternative literatures, including research on interest groups and nonstate advocacy, we call for a broader theory of transnational governance that integrates steering and influence in a way that accounts for the full array of nonstate and substate engagements beyond the state.

scholarly journals Global streamflow and flood response to stratospheric aerosol geoengineering

2018 ◽  
Author(s):  
Liren Wei ◽  
Duoying Ji ◽  
Chiyuan Miao ◽  
John C. Moore
Keyword(s):  
Return Period ◽  
Flood Risk ◽  
Large Scale ◽  
Hydrological Cycle ◽  
Stratospheric Aerosol ◽  
Model Intercomparison ◽  
Geographic Pattern ◽  
Solar Geoengineering ◽  
Intercomparison Project ◽  
Future Warming

Abstract. Flood risk is projected to increase under projections of future warming climates due to an enhanced hydrological cycle. Solar geoengineering is known to reduce precipitation and slowdown the hydrological cycle, and may be therefore be expected to offset increased flood risk. We examine this hypothesis using streamflow and river discharge responses to the representative concentration pathway RCP4.5 and Geoengineering Model Intercomparison Project (GeoMIP) G4 experiments. We also calculate changes in 30, 50, 100-year flood return periods relative to the historical (1960–1999) period under the RCP4.5 and G4 scenarios. Similar spatial patterns are produced for each return period, although those under G4 are closer to historical values than under RCP4.5. Under G4 generally lower streamflows are produced on the western sides of Eurasia and North America, with higher flows on their eastern sides. In the southern hemisphere northern parts of the land masses have lower streamflow under G4, and southern parts increases relative to RCP4.5. So in general solar geoengineering does appear to reduce flood risk in most regions, but the relative effects are largely determined by this large scale geographic pattern. Both streamflow and return period show increased drying of the Amazon under both RCP4.5 and G4 scenarios, with more drying under G4.

scholarly journals Global streamflow and flood response to stratospheric aerosol geoengineering

2018 ◽  
Vol 18 (21) ◽  
pp. 16033-16050 ◽  
Author(s):  
Liren Wei ◽  
Duoying Ji ◽  
Chiyuan Miao ◽  
Helene Muri ◽  
John C. Moore
Keyword(s):  
Return Period ◽  
Flood Risk ◽  
Large Scale ◽  
Hydrological Cycle ◽  
Stratospheric Aerosol ◽  
Model Intercomparison ◽  
Geographic Pattern ◽  
Solar Geoengineering ◽  
Intercomparison Project ◽  
Future Warming

Abstract. Flood risk is projected to increase under future warming climates due to an enhanced hydrological cycle. Solar geoengineering is known to reduce precipitation and slow down the hydrological cycle and may therefore be expected to offset increased flood risk. We examine this hypothesis using streamflow and river discharge responses to Representative Concentration Pathway 4.5 (RCP4.5) and the Geoengineering Model Intercomparison Project (GeoMIP) G4 scenarios. Compared with RCP4.5, streamflow on the western sides of Eurasia and North America is increased under G4, while the eastern sides see a decrease. In the Southern Hemisphere, the northern parts of landmasses have lower streamflow under G4, and streamflow of southern parts increases relative to RCP4.5. We furthermore calculate changes in 30-, 50-, and 100-year flood return periods relative to the historical (1960–1999) period under the RCP4.5 and G4 scenarios. Similar spatial patterns are produced for each return period, although those under G4 are closer to historical values than under RCP4.5. Hence, in general, solar geoengineering does appear to reduce flood risk in most regions, but the overall effects are largely determined by this large-scale geographic pattern. Although G4 stratospheric aerosol geoengineering ameliorates the Amazon drying under RCP4.5, with a weak increase in soil moisture, the decreased runoff and streamflow leads to an increased flood return period under G4 compared with RCP4.5.

The Double-ITCZ Bias in CMIP6 Models

2020 ◽  
Author(s):  
Baijun Tian
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Coupled Model ◽  
Global Climate Models ◽  
Cmip5 Models ◽  
Tropical Precipitation ◽  
Double Itcz ◽  
Intercomparison Project ◽  
Fully Coupled

<p>The double-Intertropical Convergence Zone (ITCZ) bias is one of the most outstanding problems in climate models. This study seeks to examine the double-ITCZ bias in the latest state-of-the-art fully coupled global climate models that participated in Coupled Model Intercomparison Project (CMIP) Phase 6 (CMIP6) in comparison to their previous generations (CMIP3 and CMIP5 models). To that end, we have analyzed the long-term annual mean tropical precipitation distributions and several precipitation bias indices that quantify the double-ITCZ biases in 75 climate models including 24 CMIP3 models, 25 CMIP3 models, and 26 CMIP6 models. We find that the double-ITCZ bias and its big inter-model spread persist in CMIP6 models but the double-ITCZ bias is slightly reduced from CMIP3 or CMIP5 models to CMIP6 models.</p>

Progress towards coupling ice sheet and ocean models

2020 ◽  
Author(s):  
Ben Galton-Fenzi ◽  
Rupert Gladstone ◽  
Chen Zhao ◽  
David Gwyther ◽  
John Moore ◽  
...  
Keyword(s):  
Global Climate ◽  
Ice Sheet ◽  
Coupled Model ◽  
Greenland Ice Sheet ◽  
Coupled System ◽  
Ocean Model ◽  
Climate Impacts ◽  
Ocean Modelling ◽  
Recent Developments ◽  
Intercomparison Project

<p>With recent developments in the modelling of Antarctica and its interactions with the ocean several coupled model frameworks now exist.  This talk will focus on presenting the Framework for Ice Sheet - Ocean Coupling (FISOC), developed to provide a flexible platform for performing coupled ice sheet - ocean modelling experiments. We present progress and preliminary results using FISOC to couple the Regional Ocean Modelling System (ROMS) with Elmer/Ice, a full-Stokes ice sheet model. Idealised experiments have been used that also contribute to the WCRP Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP).  A recent focus is on testing emergent behaviour of the coupled system and the model numerics. The talk will outline future technological applications and developments conducted as part of a broader international consortium effort. These efforts include coupling to sub-glacial hydrology, sea ice and atmospheres to form a complete system-downscaling technology from which to examine the influence of future climate on ice sheet evolution and hence sea level and global climate impacts. Developments to apply the technology to the Greenland Ice Sheet are presently underway.</p>

scholarly journals Comparing different generations of idealized solar geoengineering simulations in the Geoengineering Model Intercomparison Project (GeoMIP)

2021 ◽  
Vol 21 (6) ◽  
pp. 4231-4247
Author(s):  
Ben Kravitz ◽  
Douglas G. MacMartin ◽  
Daniele Visioni ◽  
Olivier Boucher ◽  
Jason N. S. Cole ◽  
...  
Keyword(s):  
Climate Models ◽  
Net Primary Productivity ◽  
Hydrological Cycle ◽  
Co2 Concentration ◽  
Global Scale ◽  
Model Intercomparison ◽  
Two Generations ◽  
Temporary Solution ◽  
Solar Geoengineering ◽  
Intercomparison Project

Abstract. Solar geoengineering has been receiving increased attention in recent years as a potential temporary solution to offset global warming. One method of approximating global-scale solar geoengineering in climate models is via solar reduction experiments. Two generations of models in the Geoengineering Model Intercomparison Project (GeoMIP) have now simulated offsetting a quadrupling of the CO2 concentration with solar reduction. This simulation is idealized and designed to elicit large responses in the models. Here, we show that energetics, temperature, and hydrological cycle changes in this experiment are statistically indistinguishable between the two ensembles. Of the variables analyzed here, the only major differences involve highly parameterized and uncertain processes, such as cloud forcing or terrestrial net primary productivity. We conclude that despite numerous structural differences and uncertainties in models over the past two generations of models, including an increase in climate sensitivity in the latest generation of models, the models are consistent in their aggregate climate response to global solar dimming.

scholarly journals Comparing different generations of idealized solar geoengineering simulations in the Geoengineering Model Intercomparison Project (GeoMIP)

2020 ◽  
Author(s):  
Ben Kravitz ◽  
Douglas G. MacMartin ◽  
Daniele Visioni ◽  
Olivier Boucher ◽  
Jason N. S. Cole ◽  
...  
Keyword(s):  
Climate Models ◽  
Net Primary Productivity ◽  
Hydrological Cycle ◽  
Co2 Concentration ◽  
Global Scale ◽  
Model Intercomparison ◽  
Cloud Forcing ◽  
Temporary Solution ◽  
Solar Geoengineering ◽  
Intercomparison Project

Abstract. Solar geoengineering has been receiving increased attention in recent years as a potential temporary solution to offset global warming. One method of approximating global-scale solar geoengineering in climate models is via solar reduction experiments. Two generations of models in the Geoengineering Model Intercomparison Project (GeoMIP) have now simulated offsetting a quadrupling of the CO2 concentration with solar reduction. This simulation is artificial and designed to elicit large responses in the models. Here we show that energetics, temperature, and hydrological cycle changes in this experiment are statistically indistinguishable between the two ensembles. Of the variables analyzed here, the only major differences involve highly parameterized and uncertain processes, such as cloud forcing or terrestrial net primary productivity. We conclude that despite numerous structural differences and uncertainties in models over the past 20 years, including an increase in climate sensitivity in the latest generation of models, broad conclusions about the climate response to global solar dimming remain robust.

scholarly journals Large-scale features and evaluation of the PMIP4-CMIP6 <i>midHolocene</i> simulations

2020 ◽  
Vol 16 (5) ◽  
pp. 1847-1872 ◽  
Author(s):  
Chris M. Brierley ◽  
Anni Zhao ◽  
Sandy P. Harrison ◽  
Pascale Braconnot ◽  
Charles J. R. Williams ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Hydrological Cycle ◽  
Global Climate ◽  
Coupled Model ◽  
Global Climate Models ◽  
Current Phase ◽  
Model Intercomparison ◽  
Global Mean Temperature ◽  
Intercomparison Project

Abstract. The mid-Holocene (6000 years ago) is a standard time period for the evaluation of the simulated response of global climate models using palaeoclimate reconstructions. The latest mid-Holocene simulations are a palaeoclimate entry card for the Palaeoclimate Model Intercomparison Project (PMIP4) component of the current phase of the Coupled Model Intercomparison Project (CMIP6) – hereafter referred to as PMIP4-CMIP6. Here we provide an initial analysis and evaluation of the results of the experiment for the mid-Holocene. We show that state-of-the-art models produce climate changes that are broadly consistent with theory and observations, including increased summer warming of the Northern Hemisphere and associated shifts in tropical rainfall. Many features of the PMIP4-CMIP6 simulations were present in the previous generation (PMIP3-CMIP5) of simulations. The PMIP4-CMIP6 ensemble for the mid-Holocene has a global mean temperature change of −0.3 K, which is −0.2 K cooler than the PMIP3-CMIP5 simulations predominantly as a result of the prescription of realistic greenhouse gas concentrations in PMIP4-CMIP6. Biases in the magnitude and the sign of regional responses identified in PMIP3-CMIP5, such as the amplification of the northern African monsoon, precipitation changes over Europe, and simulated aridity in mid-Eurasia, are still present in the PMIP4-CMIP6 simulations. Despite these issues, PMIP4-CMIP6 and the mid-Holocene provide an opportunity both for quantitative evaluation and derivation of emergent constraints on the hydrological cycle, feedback strength, and potentially climate sensitivity.

scholarly journals Optimal Geometric Characterization of Forced Zonal Mean Tropical Precipitation Changes.

2021 ◽  
Author(s):  
Aaron Donohoe ◽  
Alyssa R Atwood ◽  
David S Battisti
Keyword(s):  
Last Glacial Maximum ◽  
Climate Models ◽  
Global Climate ◽  
Glacial Maximum ◽  
Global Climate Models ◽  
Last Glacial ◽  
Tropical Precipitation ◽  
Precipitation Changes ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract The zonal and annual mean tropical precipitation response to paleoclimate and anthropogenic forcing scenarios ranging from the Last Glacial Maximum (LGM), CO2 quadrupling (4XCO2 ), mid-Holocene, North Atlantic freshwater hosing and volcanic forcing is analyzed in an ensemble of global climate models. Zonally averaged tropical precipitation changes are characterized in terms of three geometric manipulations of the climatological precipitation (hereafter, modes): meridional shifts, intensifications, and meridional contractions. We employ an optimization procedure that quantifies the magnitude and robustness (across different models) of changes in each mode in response to each forcing type. Additionally, the fraction of precipitation changes that are explained by the modes (in isolation and combined) is quantified. Shifts are generally less than 1º latitude in magnitude and explain a small fraction (<10%) of tropical precipitation changes. Contractions and intensifications are strongly anti-correlated across all simulations with a robust intensification and contraction of precipitation under global warming and a robust reduction and expansion under global cooling during the Last Glacial Maximum. The near constant scaling between contractions and intensifications across all simulations is used to define a joint contraction/intensification (CI) mode of tropical precipitation. The CI mode explains nearly 50% of the precipitation change under 4XCO2 and LGM forcing by optimizing a single parameter. These results suggest the shifting mode that has been extensively used to interpret paleo-rainfall reconstructions is of limited use for characterizing forced zonal mean precipitation changes and advocates for a reinterpretation of past precipitation changes to account for the CI mode

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