SOLAR GEOENGINEERING WEEKLY SUMMARY (01 APRIL - 07 APRIL 2024)
Geoengineering News
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RESEARCH PAPERS
Radiative forcing geoengineering causes higher risk of wildfires and permafrost thawing over the Arctic regions
Müller, R. C., Kim, J. S., Lee, H., Muri, H., Tjiputra, J., Yoon, J. H., & Schaepman-Strub, G. (2024). Radiative forcing geoengineering causes higher risk of wildfires and permafrost thawing over the Arctic regions. Communications Earth & Environment, 5(1), 180.
Abstract
Radiative forcing geoengineering is discussed as an intermediate solution to partially offset greenhouse gas-driven warming by altering the Earth’s energy budget. Here we use an Earth System Model to analyse the response in Arctic temperatures to radiative geoengineering applied under the representative concentration pathway 8.5 to decrease the radiative forcing to that achieved under the representative concentration pathway 4.5. The three methods Stratospheric Aerosol Injection, Marine Cloud Brightening, and Cirrus Cloud Thinning, mitigate the global mean temperature rise, however, under our experimental designs, the projected Arctic temperatures are higher than if the same temperature was achieved under emission mitigation. The maximum temperature increase under Cirrus Cloud Thinning and Marine Cloud Brightening is linked to carbon dioxide plant physiological forcing, shifting the system into climatic conditions favouring the development of fires. Under Stratospheric Aerosol Injection, the Arctic land with temperatures permanently below freezing decreased by 7.8% compared to the representative concentration pathway 4.5. This study concludes that these specific radiative forcing geoengineering designs induce less efficient cooling of the Arctic than the global mean and worsen extreme conditions compared to the representative concentration pathway 4.5.
Ecohydrological responses to solar radiation changes
Wang, Y., Meili, N., & Fatichi, S. (2024). Ecohydrological responses to solar radiation changes. EGUsphere, 2024, 1-24.
Abstract
The potential implementation of future geoengineering projects alters solar radiation to counteract global warming trends. These changes could have effects on ecohydrological systems with impacts which are still poorly quantified. Here, we compute how changes in solar radiation affect global and local near surface meteorological variables by using CMIP6 scenario results and we compute climate sensitivities to solar radiation. These sensitivities are used to construct two sets of numerical experiments: the first focuses on solar radiation changes only, and the second systematically modifies precipitation, air temperature, specific humidity, and wind speed using the CMIP6 derived sensitivities to radiation changes, i.e., including its climate feedback. We use those scenarios as input to a mechanistic ecohydrological model to quantify the responses of the energy and water budget as well as vegetation productivity spanning different biomes and climates.
In the absence of climate feedback, changes in solar radiation tend to reflect mostly in sensible heat changes, with minor effects on the hydrological cycle and vegetation productivity correlates linearly with changes in solar radiation. When climate feedback is included, changes in latent heat and hydrological variables are much more pronounced, mostly because of the temperature and vapor pressure deficit changes associated with solar radiation changes. Vegetation productivity tends to have an asymmetric response with a considerable decrease in gross primary production to a radiation reduction not accompanied by a similar increase with a radiation increase. These results provide important insights on how ecosystems could respond to potential future solar geoengineering programs.
Recent reductions in aerosol emissions have increased Earth’s energy imbalance
Hodnebrog, Ø., Myhre, G., Jouan, C., Andrews, T., Forster, P. M., Jia, H., ... & Schulz, M. (2024). Recent reductions in aerosol emissions have increased Earth’s energy imbalance. Communications Earth & Environment, 5(1), 166.
Abstract
The Earth’s energy imbalance is the net radiative flux at the top-of-atmosphere. Climate model simulations suggest that the observed positive imbalance trend in the previous two decades is inconsistent with internal variability alone and caused by anthropogenic forcing and the resulting climate system response. Here, we investigate anthropogenic contributions to the imbalance trend using climate models forced with observed sea-surface temperatures. We find that the effective radiative forcing due to anthropogenic aerosol emission reductions has led to a 0.2 ± 0.1 W m−2 decade−1 strengthening of the 2001–2019 imbalance trend. The multi-model ensemble reproduces the observed imbalance trend of 0.47 ± 0.17 W m−2 decade−1 but with 10-40% underestimation. With most future scenarios showing further rapid reductions of aerosol emissions due to air quality legislation, such emission reductions may continue to strengthen Earth’s energy imbalance, on top of the greenhouse gas contribution. Consequently, we may expect an accelerated surface temperature warming in this decade.
Public opinion about solar radiation management: A cross-cultural study in 20 countries around the world
Contzen, N., Perlaviciute, G., Steg, L., Reckels, S. C., Alves, S., Bidwell, D., ... & Sütterlin, B. (2024). Public opinion about solar radiation management: A cross-cultural study in 20 countries around the world. Climatic Change, 177(4), 1-25.
Abstract
Some argue that complementing climate change mitigation measures with solar radiation management (SRM) might prove a last resort to limit global warming to 1.5 °C. To make a socially responsible decision on whether to use SRM, it is important to consider also public opinion, across the globe and particularly in the Global South, which would face the greatest risks from both global warming and SRM. However, most research on public opinion about SRM stems from the Global North. We report findings from the first large-scale, cross-cultural study on the public opinion about SRM among the general public (N = 2,248) and students (N = 4,583) in 20 countries covering all inhabited continents, including five countries from the Global South and five ‘non-WEIRD’ (i.e. not Western, Educated, Industrialised, Rich, and Democratic) countries from the Global North. As public awareness of SRM is usually low, we provided participants with information on SRM, including key arguments in favour of and against SRM that appear in the scientific debate. On average, acceptability of SRM was significantly higher in the Global South than in the ‘non-WEIRD’ Global North, while acceptability in the ‘WEIRD’ Global North was in between. However, we found substantial variation within these clusters, especially in the ‘non-WEIRD’ Global North, suggesting that countries do not form homogenous clusters and should thus be considered individually. Moreover, the average participants’ views, while generally neither strong nor polarised, differed from some expert views in important ways, including that participants perceived SRM as only slightly effective in limiting global warming. Still, our data suggests overall a conditional, reluctant acceptance. That is, while on average, people think SRM would have mostly negative consequences, they may still be willing to tolerate it as a potential last resort to fight global warming, particularly if they think SRM has only minor negative (or even positive) impacts on humans and nature.
Solar radiation modification challenges decarbonization with renewable solar energy
Baur, S., Sanderson, B. M., Séférian, R., & Terray, L. (2023). Solar Radiation Modification challenges decarbonization with renewable solar energy. EGUsphere, 2023, 1-22.
Abstract
Solar radiation modification (SRM) is increasingly being discussed as a potential tool to reduce global and regional temperatures to buy time for conventional carbon mitigation measures to take effect. However, most simulations to date assume SRM to be an additive component to the climate change toolbox, without any physical coupling between mitigation and SRM. In this study we analyze one aspect of this coupling: how renewable energy (RE) capacity, and therefore decarbonization rates, may be affected under SRM deployment by modification of photovoltaic (PV) and concentrated solar power (CSP) production potential. Simulated 1 h output from the Earth system model CNRM-ESM2-1 for scenario-based experiments is used for the assessment. The SRM scenario uses stratospheric aerosol injections (SAIs) to approximately lower global mean temperature from the high-emission scenario SSP585 baseline to the moderate-emission scenario SSP245. We find that by the end of the century, most regions experience an increased number of low PV and CSP energy weeks per year under SAI compared to SSP245. Compared to SSP585, while the increase in low energy weeks under SAI is still dominant on a global scale, certain areas may benefit from SAI and see fewer low PV or CSP energy weeks. A substantial part of the decrease in potential with SAI compared to the SSP scenarios is compensated for by optically thinner upper-tropospheric clouds under SAI, which allow more radiation to penetrate towards the surface. The largest relative reductions in PV potential are seen in the Northern and Southern Hemisphere midlatitudes. Our study suggests that using SAI to reduce high-end global warming to moderate global warming could pose increased challenges for meeting energy demand with solar renewable resources.
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CONFERENCE PAPERS
Targeted Climate Modification on land – A matter of scale
Dekker, S. C., de Boer, H. J., Koren, G. B., Staal, A., Theeuwen, J. J., & van Woesik, F. M. (2024). Targeted Climate Modification on land–A matter of scale (No. EGU24-4740). Copernicus Meetings.
Abstract
Geoengineering strategies can be classified into two primary categories: i) Solar Radiation Management (SRM), which aims to mitigate the absorption of sunlight by the Earth, and ii) Carbon Dioxide Removal (CDR), involving the active extraction of carbon from the atmosphere for storage in terrestrial or marine environments. The ongoing discourse on geoengineering, particularly SRM on a global scale, is marked by polarization, primarily due to the challenging nature of predicting remote consequences.
This presentation endeavors to demonstrate two key points. Firstly, it will present a range of evidence indicating that local mitigation and adaptation, employing ecohydrological processes in regional models, yield more pronounced effects on regional temperatures and moisture compared to studies that use global climate models. Secondly, it will highlight that various bottom-up interventions in the energy-carbon-water nexus significantly impact maximum temperatures and moisture availability. For instance, a recent review (van Woesik et al., 2024) identifies over 50 of such interventions for East Africa.
While advocating for the efficacy of local solutions, this presentation acknowledges that such interventions, including reforestation and afforestation (e.g. Staal et al. 2024), can lead to remote consequences due to the interconnected energy-carbon-water dynamics, affecting for instance shifts in local precipitation patterns (e.g. van Theeuwen et al. 2024). Consequently, local-scale CDR solutions influence both local and remote energy balances, blurring the distinction from SRM. This challenges the applicability of conventional IPCC terminologies for climate mitigation and adaptation at the local scale. The prevalent global focus of IPCC research, derived from global models, has impeded the analysis of local ecohydrological interventions.
The central proposition of our research is that Targeted Climate Modification should be approached and analyzed from a bottom-up perspective rather than a top-down one. Therefore, we propose terminology shifts from mitigation and adaptation to Targeted Climate Modification. We hypothesize that such locally targeted interventions can benefit humanity and biodiversity by inducing cooling, enhancing agricultural productivity, and mitigating extremes in droughts and floods.
However, our research also calls for ethical and governance discussions. Acknowledging that local Targeted Climate Modification may yield negative remote consequences and substantial impacts on biodiversity loss, it advocates for the development of a new framework to analyze ethical, social, and environmental issues associated with Targeted Climate Modification.
WEB POSTS
The Solar Geoengineering Updates Newsletter (March'2024)
Solar Geoengineering UpdatesWarming Is Getting Worse. So They Just Tested a Way to Deflect the Sun (The New York Times)
The hard lessons of Harvard’s failed geoengineering experiment (MIT Technology Review)
New Climate Studies and Public Engagement Center Launch in the San Francisco Bay Area (PR Newswire)
Climate engineering carries serious national security risks − countries facing extreme heat may try it anyway, and the world needs to be prepared (The Conversation)
Climate engineering carries serious national security risks—countries facing extreme heat may try it anyway (Phys.Org)
Why artificial submarine curtains won't save West Antarctica's retreating glaciers (Phys.Org)
Geoengineering Techniques Assessment: Arctic, Antarctic and Amazonian Regions (Arctic and North Atlantic Oceans)
Tennessee outlaws release of airborne chemicals (BBC)
REPORTS
Field Study of Controlled-Release Sea Salt Aerosol Plume
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UPCOMING EVENTS
(NEW) Solar Climate Intervention Virtual Symposia#10 | 12 April 2024
(NEW) Energy Policy Seminar: "Frosted Tips: An Alternative Rationale for Solar Geoengineering" by Harvard Kennedy School | 15 April 2024
(NEW) Active Conservation of Ice-Sheets to Mitigate Sea-Level Rise: Research Needs and Approaches at EGU Meeting in Vienna, Austria | 15 April 2024
(NEW) Simulating ice sheet interventions: research methods and needs at EGU Meeting in Vienna, Austria | 15 April 2024
Solar Radiation Modification, Clouds, Aerosols, and their Impacts on the Biosphere and Earth System | EGU General Assembly | 18 April 2024
Fourteenth GeoMIP Workshop | Ithaca, USA | 10-12 July 2024
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JOB OPPORTUNITY
Researcher on the scientific and technical definition of solar geoengineering field trials for the development of a governance framework (M/F) at CNRS | Deadline: 23 April 2024
"The postdoctoral fellow will participate in the EU-funded Co-CREATE (Conditions for Responsible Research of SRM - Analysis, Co-Creation, and Ethos) project on the governance of solar geoengineering (SRM) research, and will work in particular on the scientific and technical definition of potential field trials.
As part of this project, IPSL is leading a working group (WP) on the scientific evaluation of potential solar radiation management trials in selected study cases, particularly in terms of scientific merit, monitoring, of detectability, safety limits and possible shutdown procedures, and on the boundary between an experiment and a real deployment. The working group analyzes potential future field trials from a physical science perspective and proposes quantitative estimates of identified key parameters (including ranges and uncertainties, where possible). The analyzes examine (if necessary specifically for each SRM technique): i) the boundary (physical demarcation) between research and deployment, ii) the main unknowns and the contributions that field trials can make to answer them (scientific merit), iii) environmental consequences of field trials (including their reversibility and uncertainties), iv) monitoring capabilities (to detect and attribute observed changes). In addition to conducting research on the above topics, the postdoctoral fellow will lead and co-author literature reviews on SRM field trials and participate in an international workshop. As the project is interdisciplinary, this position offers an excellent opportunity to interact with researchers in the social sciences and humanities, in particular through a WP which brings together all the contributions from the different fields. Dissemination and awareness activities are also planned."
PODCASTS
An Engineering Experiment to Cool the Earth | The Daily
"Decades of efforts to cut carbon emissions have failed to significantly slow the rate of global warming, so scientists are now turning to bolder approaches.
Christopher Flavelle, who writes about climate change for The Times, discusses efforts to engineer our way out of the climate crisis.”
Ulrike Lohmann on clouds, aerosols and solar radiation modification | Challenging Climate
"Today’s guest is Ulrike Lohmann, Professor of Experimental Atmospheric Physics in the Institute for Atmospheric and Climate Science at ETH Zurich. Lohmann is also the Principal Investigator of the CLOUDLAB project, a multi-year project to investigate aerosol-cloud interactions in wintertime stratus clouds over the Alps.
In this episode, we discuss the role of clouds and aerosols in our climate. We dive deep into aerosol-cloud interactions to uncover the science behind solar radiation modification (SRM) techniques like marine cloud brightening, and discuss a novel proposed SRM technique - Mixed Phase Cloud Thinning."