| SOLAR GEOENGINEERING WEEKLY SUMMARY (17 JUNE - 23 JUNE 2024 Subscribe to our newsletter to receive monthly updates on Solar Geoengineering:
RESEARCH PAPERSWan, J. S., Fasullo, J. T., Rosenbloom, N., Chen, C. C. J., & Ricke, K. (2024). Targeted marine cloud brightening can dampen El Ni\~ no. arXiv preprint arXiv:2406.07853. Abstract Many record-breaking climate extremes arise from both greenhouse gas-induced warming and natural climate variability. Marine cloud brightening, a solar geoengineering strategy originally proposed to reduce long-term warming, could potentially mitigate extreme events by instead targeting seasonal phenomena, such as El Niño-Southern Oscillation (ENSO). By exploiting the 2019-2020 Australian wildfire experiment-of-opportunity, we show that simulated marine cloud brightening in the southeast Pacific reproduces observed cloud changes and induces La Niña-like responses. We then explore how cloud brightening timing and duration modifies the 1997-1998 and 2015-2016 El Niño events. We find the earliest and longest interventions effectively restore neutral ENSO conditions and dampen El Niño's impacts. Solar geoengineering that targets climate variability could complement tools such as ENSO forecasting and provide a pathway for climate risk mitigation.
Wan, J.S., Chen, CC.J., Tilmes, S. et al. Diminished efficacy of regional marine cloud brightening in a warmer world. Nat. Clim. Chang. (2024). Abstract Marine cloud brightening (MCB) is a geoengineering proposal to cool atmospheric temperatures and reduce climate change impacts. As large-scale approaches to stabilize global mean temperatures pose governance challenges, regional interventions may be more attractive near term. Here we investigate the efficacy of regional MCB in the North Pacific to mitigate extreme heat in the Western United States. Under present-day conditions, we find MCB in the remote mid-latitudes or proximate subtropics reduces the relative risk of dangerous summer heat exposure by 55% and 16%, respectively. However, the same interventions under mid-century warming minimally reduce or even increase heat stress in the Western United States and across the world. This loss of efficacy may arise from a state-dependent response of the Atlantic Meridional Overturning Circulation to both anthropogenic warming and regional MCB. Our result demonstrates a risk in assuming that interventions effective under certain conditions will remain effective as the climate continues to change.
Parry, I., Ritchie, P., Boucher, O., Cox, P., Haywood, J., Niemeier, U., ... & Visioni, D. (2024). Solar Radiation Modification is projected to increase land carbon storage and to protect the Amazon rainforest. Abstract Solar radiation modification (SRM) aims to artificially cool the Earth, counteracting warming from anthropogenic greenhouse gases by increasing the reflection of incoming sunlight. One SRM strategy is stratospheric aerosol injection (SAI), which mimics explosive volcanoes by injecting aerosols into the stratosphere. There are concerns that SAI could suppress vegetation productivity by reducing the amount of sunlight reaching the Earth’s surface and by shifting rainfall patterns. Here we examine results from five Earth System Models that use SAI to reduce the global mean temperature from that of a high emissions world (SSP585), to that of a more moderate global warming scenario (SSP245). Compared to SSP245, the SAI simulations project higher global NPP values (+15.6%) and higher land carbon storage (+5.9%), primarily because of increased CO2 fertilization. The effects of SAI are most obvious in Amazonia where notable increases in NPP (+13.8%) and land carbon storage (+8.6%) are projected compared to SSP245, as well as compared to SSP585 (+10.8% and +7.1% respectively). Our results therefore suggest that SAI could provide some protection against the risk of climate change induced Amazon forest dieback, and may in fact be a very effective method of atmospheric carbon sequestration.
Pamplany, A. (2024). Does Solar Geoengineering have any Scope in a Climate Emergency. American J Sci Edu Re: AJSER-188. Abstract Geoengineering, also called climate engineering, has been considered as one of the major responses to avert the dangerous climate change along with adaptation and mitigation since 2006. Geoengineering, especially solar radiation management (SRM), is a technological approach to combat global warming by managing the incoming solar radiation. The claim behind the coinage of geoengineering as an option to avert dangerous climate change is that it can serve as an emergency mechanism if the earth crosses the dangerous tipping points due to the anthropogenic climate changes. However, this claim of the proponents is rigorously opposed by many scientists and ethicists. This paper tries to give an objective presentation of the current debate over SRM geoengineering as a policy option in a climate emergency. The paper is developed around the research question, does geoengineering carry any potential to avert a climate emergency scenario? This is answered by analysing the main streams of arguments made by the proponents and opponents with regard to the desirability or non-desirability of SRM in a climate emergency caused by the anthropogenic climate change? This question is tried to be answered primarily by a review of literature presenting and analysing the challenges and opportunities at stake in geoengineering as an emergency option. The literature exhibits a sharp divide between the proponents and opponents of the geoengineering technologies. A definitive judgement over its desirability or non-desirability is rendered ambivalent by the prevalent scientific uncertainties, inadequate data, insufficient field tests and the unprecedented scale and range of consequences of deploying such a technology with a global outreach in the open system of the earth. The literature presents an unsettled debate in this regard. Most of the second generation of ethical deliberation over geoengineering is inclined to reject the scope of SRM geoengineering as a policy option in an emergency scenario. The discussion argues that an informed decision on the scope of solar geoengineering in an emergency scenario demands geoengineering framings specific to emergency and the greater presence of emergency scientists on the debate is recommended.
Gay, B., Miller, C., Miner, K., & Mandrake, L. (2024). Assessing Earth System Responses to Climate Mitigation and Intervention with Scenario-Based Simulations and Data-Driven Insight. Abstract Given a world increasingly dominated by climate extremes, large-scale geoengineering interventions to modify the Earth’s climate appears inevitable. However, geoengineering faces a conundrum: accurately forecasting the consequences of climate intervention in a system for which we have incomplete observations and an imperfect understanding. We evaluate the potential implications of mitigation and intervention strategies with a set of experiments utilizing historical reanalysis data and scenario-based model simulations to examine the global response to deploying these strategies. Key findings included a global mean surface temperature and total precipitation increases of 1.3740.481C and 0.0450.567 mm day−1 respectively over the observed period (i.e., 1950–2022). Mitigation and intervention simulations reveal pronounced regional anomalies in surface temperature and erratic interannual variability in total precipitation, with surface temperatures up to 7.626C in Greenland, Northern Siberia, and the Horn of Africa down to -2.378ºC in Central Africa and Eastern Brazil, and total precipitation increases of 1.170 mm day−1 in Southern Alaska down to -1.195 mm day− 1 in Colombia and East Africa. Furthermore, [CH4] dynamics indicated the potential to alter global and regional climate metrics but presented significant regional and global variability based on scenario deployment. Collectively, intervention and mitigation simulations tended to overestimate the variability and magnitude of surface temperature and total precipitation, with substantial regional deviations and scenario-dependent estimation heterogeneity for [CH4]. Furthermore, forward projections indicate that both mitigation and intervention scenarios can lead to varied climate responses, emphasizing the complexity and uncertainty in predicting exact outcomes of different geoengineering strategies. By constraining our investigation scope to include monthly surface temperature, total precipitation, and atmospheric methane concentration [CH4], we find these simulations were capable of accurately capturing departures but unable to perfectly represent patterns of warming and precipitation teleconnections clearly identified in the observational record.
Morrison, A. L., Barnes, E. A., & Hurrell, J. W. (2024). Natural variability can mask forced permafrost response to stratospheric aerosol injection in the ARISE‐SAI‐1.5 simulations. Earth's Future, 12(6), e2023EF004191. Abstract Stratospheric aerosol injection (SAI) has been proposed as a potential method for mitigating risks and impacts associated with anthropogenic climate change. One such risk is widespread permafrost thaw and associated carbon release. While permafrost has been shown to stabilize under different SAI scenarios, natural variability may mask this forced response and make it difficult to detect if and when SAI is stabilizing permafrost. Here we use the 10-member ensemble from the ARISE-SAI-1.5 simulations to assess the spread in projected active layer depth and permafrost temperature across boreal permafrost soils and specifically in four peatland and Yedoma regions. The forced response in active layer depth and permafrost temperature quickly diverges between an SAI and non-SAI world, but individual ensemble members overlap for several years following SAI deployment. We find that, due to projected permafrost variability, it may take more than a decade of SAI deployment to detect the effects of SAI on permafrost temperature and almost 30 years to detect its effects on active layer depth. Not only does natural variability make it more difficult to detect SAI's influence, it could also affect the likelihood of reaching a permafrost tipping point. In some realizations, SAI fails to prevent a local tipping point that is also reached in a non-SAI world. Our results underscore the importance of accounting for natural variability in assessments of SAI's potential influence on the climate system.
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DEADLINESSRM Sessions at AGU2024:
YOUTUBE VIDEOSThanks to Chlorine | ToSaveTheWorld "David Henkel-Wallace, Franz Oeste, Clive Elsworth, Jeff Shrager, Peter Fiekowsky, and Rocio Herbert are all exploring the new discovery that clouds (the white ones that reflect sunlight back into space) also cool the planet in another way: by adding hydrochloric acid to the atmosphere, which has an independent cooling effect by destroying methane molecules. This may give us a new way of cooling the planet. Aele Buckley has a question."
Climate Change – Solar Geoengineering as a Solution? | Österreichisches Außenministerium “This TechDiplomacyTalk aimed at deepening the understanding of solar geoengineering - technologies that cool the earth by reflecting sunlight back into space – and its associated ethical concerns, geopolitical implications and risks for the environment, biodiversity and humans. In the light of the risks, ongoing field tests and increasing private sector interest, the discussion focused on the need for global, science-based, and effective control and regulatory mechanisms for solar geoengineering. Three panellists participated in this TechDiplomacyTalk: Ambassador Salome Meyer, the Ambassador of Switzerland to Austria, Blaž Gasparini, climate physicist at the University of Vienna, specializing in the impact of clouds on climate, and Michel Tschirren, Head of the Global Affairs Section at Switzerland’s Federal Office for the Environment."
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