scholarly journals Atlantic hurricane surge response to geoengineering

2015 ◽  
Vol 112 (45) ◽  
pp. 13794-13799 ◽  
Author(s):  
John C. Moore ◽  
Aslak Grinsted ◽  
Xiaoran Guo ◽  
Xiaoyong Yu ◽  
Svetlana Jevrejeva ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Stratospheric Ozone ◽  
Storm Surges ◽  
Polar Regions ◽  
Global Mean Temperature ◽  
Intercomparison Project ◽  
Coastal Flood Risk ◽  
Atlantic Hurricanes ◽  
The One ◽  
The Tropics

Devastating floods due to Atlantic hurricanes are relatively rare events. However, the frequency of the most intense storms is likely to increase with rises in sea surface temperatures. Geoengineering by stratospheric sulfate aerosol injection cools the tropics relative to the polar regions, including the hurricane Main Development Region in the Atlantic, suggesting that geoengineering may mitigate hurricanes. We examine this hypothesis using eight earth system model simulations of climate under the Geoengineering Model Intercomparison Project (GeoMIP) G3 and G4 schemes that use stratospheric aerosols to reduce the radiative forcing under the Representative Concentration Pathway (RCP) 4.5 scenario. Global mean temperature increases are greatly ameliorated by geoengineering, and tropical temperature increases are at most half of those temperature increases in the RCP4.5. However, sulfate injection would have to double (to nearly 10 teragrams of SO2 per year) between 2020 and 2070 to balance the RCP4.5, approximately the equivalent of a 1991 Pinatubo eruption every 2 y, with consequent implications for stratospheric ozone. We project changes in storm frequencies using a temperature-dependent generalized extreme value statistical model calibrated by historical storm surges and observed temperatures since 1923. The number of storm surge events as big as the one caused by the 2005 Katrina hurricane are reduced by about 50% compared with no geoengineering, but this reduction is only marginally statistically significant. Nevertheless, when sea level rise differences in 2070 between the RCP4.5 and geoengineering are factored into coastal flood risk, we find that expected flood levels are reduced by about 40 cm for 5-y events and about halved for 50-y surges.

scholarly journals Sulfate geoengineering impact on methane transport and lifetime: results from the Geoengineering Model Intercomparison Project (GeoMIP)

2017 ◽  
Vol 17 (18) ◽  
pp. 11209-11226 ◽  
Author(s):  
Daniele Visioni ◽  
Giovanni Pitari ◽  
Valentina Aquila ◽  
Simone Tilmes ◽  
Irene Cionni ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Radiation Absorption ◽  
Coupled Models ◽  
Upper Troposphere ◽  
Aerosol Scattering ◽  
Intercomparison Project ◽  
Planetary Albedo ◽  
The Tropics

Abstract. Sulfate geoengineering (SG), made by sustained injection of SO2 in the tropical lower stratosphere, may impact the CH4 abundance through several photochemical mechanisms affecting tropospheric OH and hence the methane lifetime. (a) The reflection of incoming solar radiation increases the planetary albedo and cools the surface, with a tropospheric H2O decrease. (b) The tropospheric UV budget is upset by the additional aerosol scattering and stratospheric ozone changes: the net effect is meridionally not uniform, with a net decrease in the tropics, thus producing less tropospheric O(1D). (c) The extratropical downwelling motion from the lower stratosphere tends to increase the sulfate aerosol surface area density available for heterogeneous chemical reactions in the mid-to-upper troposphere, thus reducing the amount of NOx and O3 production. (d) The tropical lower stratosphere is warmed by solar and planetary radiation absorption by the aerosols. The heating rate perturbation is highly latitude dependent, producing a stronger meridional component of the Brewer–Dobson circulation. The net effect on tropospheric OH due to the enhanced stratosphere–troposphere exchange may be positive or negative depending on the net result of different superimposed species perturbations (CH4, NOy, O3, SO4) in the extratropical upper troposphere and lower stratosphere (UTLS). In addition, the atmospheric stabilization resulting from the tropospheric cooling and lower stratospheric warming favors an additional decrease of the UTLS extratropical CH4 by lowering the horizontal eddy mixing. Two climate–chemistry coupled models are used to explore the above radiative, chemical and dynamical mechanisms affecting CH4 transport and lifetime (ULAQ-CCM and GEOSCCM). The CH4 lifetime may become significantly longer (by approximately 16 %) with a sustained injection of 8 Tg-SO2 yr−1 starting in the year 2020, which implies an increase of tropospheric CH4 (200 ppbv) and a positive indirect radiative forcing of sulfate geoengineering due to CH4 changes (+0.10 W m−2 in the 2040–2049 decade and +0.15 W m−2 in the 2060–2069 decade).

scholarly journals Sulfate Geoengineering Impact on Methane Transport and Lifetime: Results from the Geoengineering Model Intercomparison Project (GeoMIP)

2017 ◽  
Author(s):  
Daniele Visioni ◽  
Giovanni Pitari ◽  
Valentina Aquila ◽  
Simone Tilmes ◽  
Irene Cionni ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Lower Stratosphere ◽  
Stratospheric Ozone ◽  
Radiation Absorption ◽  
Coupled Models ◽  
Upper Troposphere ◽  
Aerosol Scattering ◽  
Intercomparison Project ◽  
Planetary Albedo ◽  
The Tropics

Abstract. Sulfate geoengineering, made by sustained injection of SO2 in the tropical lower stratosphere, may impact the CH4 abundance through several photochemical mechanisms affecting tropospheric OH and hence the methane lifetime. (a) Solar radiation scattering increases the planetary albedo and cools the surface, with a tropospheric H2O decrease. (b) The tropospheric UV budget is upset by the additional aerosol scattering and stratospheric ozone changes: the net effect is meridionally not uniform, with a net decrease in the tropics, thus producing less tropospheric O(1D). (c) The extratropical downwelling motion from the lower stratosphere tends to increase the sulfate aerosol surface area density available for heterogeneous chemical reactions in the mid-upper troposphere, thus reducing the amount of NOx and O3 production. (d) The tropical lower stratosphere is warmed by solar and planetary radiation absorption by the aerosols. The heating rate perturbation is highly latitude dependent, producing a stronger meridional component of the Brewer-Dobson circulation. The net effect on tropospheric OH due to the enhanced stratosphere-troposphere exchange may be positive or negative depending on the net result of different superimposed species perturbations (CH4, NOy, O3, SO4) in the extratropical upper troposphere and lower stratosphere (UTLS). In addition, the atmospheric stabilization resulting from the tropospheric cooling and lower stratospheric warming favors an additional decrease of the UTLS extratropical CH4, by lowering the horizontal eddy mixing. Two climate-chemistry coupled models are used to explore the above radiative, chemical and dynamical mechanisms affecting CH4 transport and lifetime (ULAQ-CCM and GEOSCCM). The CH4 lifetime may become significantly longer (by approximately 16 %) with a sustained injection of 8 Tg-SO2/yr started in year 2020, which implies an increase of tropospheric CH4 (200 ppbv) and a positive indirect radiative forcing of sulfate geoengineering due to CH4 changes (+0.10 W/m2 in the 2040–2049 decade and +0.15 W/m2 in the 2060–2069 decade).

scholarly journals Seasonal impact of biogenic VSL bromine on the evolution of mid-latitude lowermost stratospheric ozone during the 21<sup>st</sup> century

2020 ◽  
Author(s):  
Javer A. Barrera ◽  
Rafael P. Fernandez ◽  
Fernando Iglesias-Suarez ◽  
Carlos A. Cuevas ◽  
Jean-Francois Lamarque ◽  
...  
Keyword(s):  
21St Century ◽  
Total Ozone ◽  
Stratospheric Ozone ◽  
Polar Regions ◽  
Total Ozone Column ◽  
Seasonal Impact ◽  
The Tropics ◽  
The Impact ◽  
Ozone Column ◽  
Modelling Study

Abstract. Biogenic very short-lived bromine (VSLBr) represents, nowadays, ~ 25 % of the total stratospheric bromine loading. Owing to their much shorter lifetime compared to anthropogenic long-lived bromine (LLBr, e.g., halons) and chlorine (LLCl, e.g., chlorofluorocarbons) substances, the impact of VSLBr on ozone peaks at the extratropical lowermost stratosphere, a key climatic and radiative atmospheric region. Here we present a modelling study of the evolution of stratospheric ozone and its chemical losses in extra-polar regions during the 21st century, under two different scenarios: considering and neglecting the additional stratospheric injection of 5 ppt biogenic VSLBr naturally released from the ocean. Our analysis shows that the inclusion of VSLBr result in a realistic stratospheric bromine loading and improves the quantitative 1980–2015 model-satellite agreement of total ozone column (TOC) in the mid-latitudes. We show that the overall ozone response to VSLBr within the mid-latitudes follows the stratospheric abundances evolution of long-lived inorganic chlorine and bromine throughout the 21st century. Additional ozone losses due to VSLBr are maximised during the present-day period (1990–2010), with TOC differences of −8 DU (−3 %) and −5.5 DU (−2 %) for the southern (SH-ML) and northern (NH-ML) mid-latitudes, respectively. Moreover, the projected TOC differences at the end of the 21st century are at least half of the values found for the present-day period. In the tropics, a small (

scholarly journals Energy transport, polar amplification, and ITCZ shifts in the GeoMIP G1 ensemble

2018 ◽  
Vol 18 (3) ◽  
pp. 2287-2305 ◽  
Author(s):  
Rick D. Russotto ◽  
Thomas P. Ackerman
Keyword(s):  
Radiative Forcing ◽  
Climate Models ◽  
Energy Transport ◽  
Global Climate Models ◽  
Balance Model ◽  
Polar Regions ◽  
Model Intercomparison ◽  
Polar Amplification ◽  
Solar Geoengineering ◽  
Intercomparison Project

Abstract. The polar amplification of warming and the ability of the Intertropical Convergence Zone (ITCZ) to shift to the north or south are two very important problems in climate science. Examining these behaviors in global climate models (GCMs) running solar geoengineering experiments is helpful not only for predicting the effects of solar geoengineering but also for understanding how these processes work under increased carbon dioxide (CO2). Both polar amplification and ITCZ shifts are closely related to the meridional transport of moist static energy (MSE) by the atmosphere. This study examines changes in MSE transport in 10 fully coupled GCMs in experiment G1 of the Geoengineering Model Intercomparison Project (GeoMIP), in which the solar constant is reduced to compensate for the radiative forcing from abruptly quadrupled CO2 concentrations. In G1, poleward MSE transport decreases relative to preindustrial conditions in all models, in contrast to the Coupled Model Intercomparison Project phase 5 (CMIP5) abrupt4xCO2 experiment, in which poleward MSE transport increases. We show that since poleward energy transport decreases rather than increases, and local feedbacks cannot change the sign of an initial temperature change, the residual polar amplification in the G1 experiment must be due to the net positive forcing in the polar regions and net negative forcing in the tropics, which arise from the different spatial patterns of the simultaneously imposed solar and CO2 forcings. However, the reduction in poleward energy transport likely plays a role in limiting the polar warming in G1. An attribution study with a moist energy balance model shows that cloud feedbacks are the largest source of uncertainty regarding changes in poleward energy transport in midlatitudes in G1, as well as for changes in cross-equatorial energy transport, which are anticorrelated with ITCZ shifts.

scholarly journals Cloud radiative forcing intercomparison between fully coupled CMIP5 models and CERES satellite data

2014 ◽  
Vol 32 (7) ◽  
pp. 793-807 ◽  
Author(s):  
M. Calisto ◽  
D. Folini ◽  
M. Wild ◽  
L. Bengtsson
Keyword(s):  
Radiative Forcing ◽  
Cloud Cover ◽  
Coupled Model ◽  
Cmip5 Models ◽  
Radiative Fluxes ◽  
Cloud Radiative Forcing ◽  
Summer Hemisphere ◽  
Intercomparison Project ◽  
Annual Means ◽  
The Tropics

Abstract. In this paper, radiative fluxes for 10 years from 11 models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) and from CERES satellite observations have been analyzed and compared. Under present-day conditions, the majority of the investigated CMIP5 models show a tendency towards a too-negative global mean net cloud radiative forcing (NetCRF) as compared to CERES. A separate inspection of the long-wave and shortwave contribution (LWCRF and SWCRF) as well as cloud cover points to different shortcomings in different models. Models with a similar NetCRF still differ in their SWCRF and LWCRF and/or cloud cover. Zonal means mostly show excessive SWCRF (too much cooling) in the tropics between 20° S and 20° N and in the midlatitudes between 40 to 60° S. Most of the models show a too-small/too-weak LWCRF (too little warming) in the subtropics (20 to 40° S and N). Difference maps between CERES and the models identify the tropical Pacific Ocean as an area of major discrepancies in both SWCRF and LWCRF. The summer hemisphere is found to pose a bigger challenge for the SWCRF than the winter hemisphere. The results suggest error compensation to occur between LWCRF and SWCRF, but also when taking zonal and/or annual means. Uncertainties in the cloud radiative forcing are thus still present in current models used in CMIP5.

scholarly journals Extreme temperature and precipitation response to solar dimming and stratospheric aerosol geoengineering

2018 ◽  
Author(s):  
Duoying Ji ◽  
Songsong Fang ◽  
Charles L. Curry ◽  
Hiroki Kashimura ◽  
Shingo Watanabe ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Extreme Temperature ◽  
Stratospheric Aerosol ◽  
Aerosol Direct Effect ◽  
Temperature And Precipitation ◽  
Intercomparison Project ◽  
Lower Maximum ◽  
Maximum Temperatures ◽  
Subtropical Oceans ◽  
The Tropics

Abstract. We examine extreme temperature and precipitation under two potential geoengineering methods forming part of the Geoengineering Model Intercomparison Project (GeoMIP). The solar dimming experiment G1 is designed to completely offset the global mean radiative forcing due to a CO2-quadrupling experiment (abrupt 4 × CO2), while in GeoMIP experiment G4, the radiative forcing due to the representative concentration pathway 4.5 (RCP4.5) scenario is partly offset by a simulated layer of aerosols in the stratosphere. Both G1 and G4 geoengineering simulations lead to lower maximum temperatures at higher latitudes, and on land primarily through feedback effects involving high latitude processes such as snow cover, sea ice and soil moisture. Maximum 5-day precipitation increases over subtropical oceans, whereas warm spells decrease markedly in the tropics, and the number of consecutive dry days decreases in most deserts. The precipitation during the tropical cyclone (hurricane) seasons becomes less intense, whilst the remainder of the year becomes wetter. Aerosol injection is more effective than dimming in moderating extreme precipitation (and flooding), possibly due to stratospheric warming by aerosol injection working in tandem with sea surface temperature reductions to moderate extreme tropical storm cyclogenesis. The differences in the response of temperature extremes between the two types of geoengineering are relatively minor. Despite the magnitude of the radiative forcing applied in G1 being ~ 6.5 times larger than in G4, and differences in the aerosol chemistry and transport schemes amongst the models, one can discern clear differences in the precipitation extremes between the types of geoengineering probably due to the aerosol direct effect and related energetic changes.

scholarly journals Nonlinear climate sensitivity and its implications for future greenhouse warming

2016 ◽  
Vol 2 (11) ◽  
pp. e1501923 ◽  
Author(s):  
Tobias Friedrich ◽  
Axel Timmermann ◽  
Michelle Tigchelaar ◽  
Oliver Elison Timm ◽  
Andrey Ganopolski
Keyword(s):  
Climate Sensitivity ◽  
Radiative Forcing ◽  
Model Simulation ◽  
Coupled Model ◽  
Glacial Cycles ◽  
Global Mean Temperature ◽  
Surface Temperatures ◽  
Intercomparison Project ◽  
Future Warming ◽  
Global Mean

Global mean surface temperatures are rising in response to anthropogenic greenhouse gas emissions. The magnitude of this warming at equilibrium for a given radiative forcing—referred to as specific equilibrium climate sensitivity (S)—is still subject to uncertainties. We estimate global mean temperature variations andSusing a 784,000-year-long field reconstruction of sea surface temperatures and a transient paleoclimate model simulation. Our results reveal thatSis strongly dependent on the climate background state, with significantly larger values attained during warm phases. Using the Representative Concentration Pathway 8.5 for future greenhouse radiative forcing, we find that the range of paleo-based estimates of Earth’s future warming by 2100 CE overlaps with the upper range of climate simulations conducted as part of the Coupled Model Intercomparison Project Phase 5 (CMIP5). Furthermore, we find that within the 21st century, global mean temperatures will very likely exceed maximum levels reconstructed for the last 784,000 years. On the basis of temperature data from eight glacial cycles, our results provide an independent validation of the magnitude of current CMIP5 warming projections.

scholarly journals Analysis of present day and future OH and methane lifetime in the ACCMIP simulations

2012 ◽  
Vol 12 (9) ◽  
pp. 22945-23005 ◽  
Author(s):  
A. Voulgarakis ◽  
V. Naik ◽  
J.-F. Lamarque ◽  
D. T. Shindell ◽  
P. J. Young ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Radiative Forcing ◽  
Climate Modeling ◽  
Stratospheric Ozone ◽  
Climate Feedback ◽  
Photolysis Rates ◽  
Emissions Scenarios ◽  
Similar Range ◽  
Rcp 8.5 ◽  
Intercomparison Project

Abstract. Results from simulations performed for the Atmospheric Chemistry and Climate Modeling Intercomparison Project (ACCMIP) are analysed to examine how OH and methane lifetime may change from present-day to the future, under different climate and emissions scenarios. Present-day (2000) mean tropospheric chemical lifetime derived from the ACCMIP multi-model mean is 9.8 ± 1.6 yr, lower than a recent observationally-based estimate, but with a similar range to previous multi-model estimates. Future model projections are based on the four Representative Concentration Pathways (RCPs), and the results also exhibit a~large range. Decreases in global methane lifetime of 4.5 ± 9.1% are simulated for the scenario with lowest radiative forcing by 2100 (RCP 2.6), while increases of 8.5 ± 10.4% are simulated for the scenario with highest radiative forcing (RCP 8.5). In this scenario, the key driver of the evolution of OH and methane lifetime is methane itself, since its concentration more than doubles by 2100, and it consumes much of the OH that exists in the troposphere. Stratospheric ozone recovery, which drives tropospheric OH decreases through photolysis modifications, also plays a~partial role. In the other scenarios, where methane changes are less drastic, the interplay between various competing drivers leads to smaller and more diverse OH and methane lifetime responses, which are difficult to attribute. For all scenarios, regional OH changes are even more variable, with the most robust feature being the large decreases over the remote oceans in RCP 8.5. Through a~regression analysis, we suggest that differences in emissions of non-methane volatile organic compounds and in the simulation of photolysis rates may be the main factors causing the differences in simulated present-day OH and methane lifetime. Diversity in predicted changes between present-day and future was found to be associated more strongly with differences in modelled climate changes, specifically global temperature and humidity. Finally, through perturbation experiments we calculated an OH feedback factor (F) of 1.29 from present-day conditions (1.65 from 2100 RCP 8.5 conditions) and a~climate feedback on methane lifetime of 0.33 ± 0.13 yr K−1, on average.

scholarly journals On the future role of the most parsimonious climate module in integrated assessment

2019 ◽  
Vol 10 (1) ◽  
pp. 135-155
Author(s):  
Mohammad M. Khabbazan ◽  
Hermann Held
Keyword(s):  
Integrated Assessment ◽  
Radiative Forcing ◽  
General Circulation ◽  
Climate Model ◽  
General Circulation Models ◽  
Box Model ◽  
Time To Peak ◽  
Global Mean Temperature ◽  
Ocean General Circulation Models ◽  
The One

Abstract. In the following, we test the validity of a one-box climate model as an emulator for atmosphere–ocean general circulation models (AOGCMs). The one-box climate model is currently employed in the integrated assessment models FUND, MIND, and PAGE, widely used in policy making. Our findings are twofold. Firstly, when directly prescribing AOGCMs' respective equilibrium climate sensitivities (ECSs) and transient climate responses (TCRs) to the one-box model, global mean temperature (GMT) projections are generically too high by 0.5 K at peak temperature for peak-and-decline forcing scenarios, resulting in a maximum global warming of approximately 2 K. Accordingly, corresponding integrated assessment studies might tend to overestimate mitigation needs and costs. We semi-analytically explain this discrepancy as resulting from the information loss resulting from the reduction of complexity. Secondly, the one-box model offers a good emulator of these AOGCMs (accurate to within 0.1 K for Representative Concentration Pathways, RCPs, namely RCP2.6, RCP4.5, and RCP6.0), provided the AOGCM's ECS and TCR values are universally mapped onto effective one-box counterparts and a certain time horizon (on the order of the time to peak radiative forcing) is not exceeded. Results that are based on the one-box model and have already been published are still just as informative as intended by their respective authors; however, they should be reinterpreted as being influenced by a larger climate response to forcing than intended.

scholarly journals Stratospheric Ozone Response to Sulfate Aerosol and Solar Dimming Climate Interventions based on the G6 Geoengineering Model Intercomparison Project (GeoMIP) Simulations

2021 ◽  
Author(s):  
Simone Tilmes ◽  
Daniele Visioni ◽  
Andy Jones ◽  
James Haywood ◽  
Roland Séférian ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Stratospheric Ozone ◽  
Sulfate Aerosol ◽  
Model Intercomparison ◽  
Total Column Ozone ◽  
Surface Climate ◽  
Intercomparison Project ◽  
Column Ozone ◽  
The Tropics ◽  
Earth System Models

Abstract. This study assesses the impacts of sulfate aerosol intervention (SAI) and solar dimming on stratospheric ozone based on the G6 Geoengineering Model Intercomparison Project (GeoMIP) experiments, called G6sulfur and G6solar. For G6sulfur the stratospheric sulfate aerosol burden is increased to reflect some of the incoming solar radiation back into space in order to cool the surface climate, while for G6solar the global solar constant is reduced to achieve the same goal. The high emissions scenario SSP5-8.5 is used as the baseline experiment and surface temperature from the medium emission scenario SSP2-4.5 is the target. Based on three out of six Earth System Models (ESMs) that include interactive stratospheric chemistry, we find significant differences in the ozone distribution between G6solar and G6sulfur experiments compared to SSP5-8.5 and SSP2-4.5, which differ by both region and season. Both SAI and solar dimming methods reduce incoming solar insolation and result in tropospheric temperatures comparable to SSP2-4.5 conditions. G6sulfur increases the concentration of absorbing sulfate aerosols in the stratosphere, which increases lower tropical stratospheric temperatures by between 5 to 13 K for six different ESMs, leading to changes in stratospheric transport. The increase of the aerosol burden also increases aerosol surface area density, which is important for heterogeneous chemical reactions. The resulting changes in ozone include a significant reduction of total column ozone (TCO) in the Southern Hemisphere polar region in October of 10 DU at the onset and up to 20 DU by the end of the century. The relatively small reduction in TCO for the multi-model mean in the first two decades results from variations in the required sulfur injections in the models and differences in the complexity of the chemistry schemes, with no significant ozone loss for 2 out of 3 models. The decrease in the second half of the 21st century counters increasing TCO between SSP2-4.5 and SSP5-8.5 due to the super-recovery resulting from increasing greenhouse gases. In contrast, in the Northern Hemisphere (NH) high latitudes, only a small initial decline in TCO is simulated, with little change in TCO by the end of the century compared to SSP5-8.5. All models consistently simulate an increase in TCO in the NH mid-latitudes up to 20 DU compared to SSP5-8.5, in addition to 20 DU increase resulting from increasing greenhouse gases between SSP2-4.5 and SSP5-8.5. G6solar counters zonal wind and tropical upwelling changes between SSP2-4.5 and SSP5-8.5 but does not change stratospheric temperatures. Solar dimming results in little change in TCO compared to SSP5-8.5 and does not counter the effects of the ozone super-recovery. Only in the tropics, G6solar results in an increase of TCO of up to 8 DU compared to SSP2-4.5, which may counter the projected reduction due to climate change in the high forcing future scenario. This work identifies differences in the response of SAI and solar dimming on ozone, which are at least partly due to differences and shortcomings in the complexity of aerosol microphysics, chemistry, and the description of ozone photolysis in the models. It also identifies that solar dimming, if viewed as an analog to SAI using a predominantly scattering aerosol, would, for the most part, not counter the potential harmful increase in TCO beyond historical values induced by increasing greenhouse gases.

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