WEEKLY SUMMARY (25 SEPTEMBER - 01 OCTOBER 2023)
Beer, C. G., Hendricks, J., & Righi, M. (2023). Impacts of ice-nucleating particles on cirrus clouds and radiation derived from global model simulations with MADE3 in EMAC. EGUsphere, 2023, 1-29.
Atmospheric aerosols can act as ice-nucleating particles (INPs) and influence the formation and the microphysical properties of cirrus clouds, resulting in distinct climate effects. We employ a global aerosol–climate model, including a two-moment cloud microphysical scheme and a parametrization for aerosol-induced ice formation in cirrus clouds, to quantify the climate impact of INPs on cirrus clouds. The model considers mineral dust, (aviation) soot, crystalline ammonium sulfate, and glassy organics as INPs in the cirrus regime. A number of sensitivity experiments are performed to analyse various aspects of the simulated INP-cirrus effect regarding (i) the ice-nucleating potential of the INPs, (ii) the inclusion of ammonium sulfate and organic particles as INPs in the model, and (iii) the model representations of vertical updrafts. The resulting global radiative forcing of the total INP-cirrus effect, considering all different INP-types, assuming a smaller and a larger ice nucleating potential of INPs, is simulated as −28 and −55 mW m−2, respectively. While the simulated impact of glassy organic INPs is mostly small and not statistically significant, ammonium sulfate INPs contribute a considerable radiative forcing, which is nearly as large as the combined effect of mineral dust and soot INPs. Additionally, the anthropogenic INP-cirrus effect is analysed considering the difference between present-day (2014) and pre-industrial conditions (1750) and amounts to −29 mW m−2. In an additional sensitivity experiment we analyse the effect of highly efficient INPs proposed for cirrus cloud seeding as a means to reduce global warming by climate engineering. However, the results indicate that this approach risks an overseeding of cirrus clouds and often results in positive radiative forcings. Idealized experiments with prescribed vertical velocities highlight the crucial role of the model dynamics for the simulated INP-cirrus effects, e.g. resulting forcings increase about one order of magnitude when increasing the prescribed vertical velocity. The large discrepancy in the magnitude of the simulated INP-cirrus effect between different model studies emphasizes the need for future detailed analyses and efforts to reduce this uncertainty and constrain the resulting climate impact of INPs.
Bakalova, I., & Belaia, M. (2023). Stability of Efficient International Agreements on Solar Geoengineering. Environmental and Resource Economics, 1-40.
Solar geoengineering (SG) may have the potential to reduce extreme climate damages worldwide. Yet, international coordination will make the difference between success and failure in leveraging it. Using a simple game-theoretic framework, we investigate whether the stability of an efficient, self-enforcing international agreement on SG is attainable. We demonstrate that side payments from countries less vulnerable to climate change to those more vulnerable can guarantee the stability of an efficient agreement. The size of the side payments will vary within a zone of possible agreement, which will change depending on certain key assumptions. For example, assuming stronger mitigation reduces the necessary payments. Alternatively, asymmetry in national damages from SG over-provision vs. under-provision justifies larger payments; here, the welfare-optimal strategy may be deployment that makes no one worse off. We also show that an agreement may be stable without side payments if deployment costs are substantial and counter-SG is available, while a moratorium may be socially optimal if SG brings substantial global non-excludable fixed costs.
Feinberg, A. (2023). Annual Solar Geoengineering: Mitigating Yearly Global Warming Increases.
Solar geoengineering (SG) solutions have many advantages compared to the difficulty of carbon removal (CR): SG produces fast results, is shown here to have much higher efficiency than CR, is not related to fossil fuel legislation, and is something we all can participate in brightening the Earth with cool roofs, and roads. SG requirements detailed previously to mitigate global warming (GW) have been concerning primarily because of overwhelming goals and climate circulation issues. In this paper, the advantages of annual solar geoengineering (ASG) to mitigate yearly global warming increases are explored and detailed as it provides higher feasibility in geoengineering applications. ASG area modification requirements found here are generally 50 to possibly higher than 150 times less compared to the challenge of full SG GW mitigation reducing circulation concerns. Results indicate that there are mixed technologies that can help meet annual mitigation Earth brightening goals. As well, results show much higher feasibility for L1 space shading compared to prior literature estimates for full GW mitigation. However, stratosphere injections appear challenging in the annual approach. Because ASG earth brightening area requirements are much smaller than those required for full mitigation, we have concerns that worldwide negative SG would interfere with making positive advances for several reasons. Negative SG currently dominates yearly practices with the application of dark asphalt roads and roofs. This issue is discussed.
Patel, T. D., Odoulami, R. C., Pinto, I., Egbebiyi, T. S., Lennard, C., Abiodun, B. J., & New, M. (2023). Potential impact of stratospheric aerosol geoengineering on projected temperature and precipitation extremes in South Africa. Environmental Research: Climate, 2(3), 035004.
Stratospheric aerosol injection (SAI) is the theoretical deployment of sulphate particles into the stratosphere to reflect incoming solar radiation and trigger a cooling impact at the Earth's surface. This study assessed the potential impact of SAI geoengineering on temperature and precipitation extremes over South Africa (SAF) and its climatic zones in the future (2075–2095) using simulations from the Stratospheric Aerosol Geoengineering Large Ensemble (GLENS) project. We analyse three different experiments from the GLENS project, each of which simulate stratospheric SO2 injection under the representative concentration pathway 8.5 (RCP8.5) emissions scenario: (i) tropical injection around 22.8–25 km altitude (GLENS), (ii) tropical injection around 1 km above the tropopause (GLENS_low), and (iii) injection near the equator around 20–25 km (GLENS_eq). The study used a set of the Expert Team on Climate Change Detection and Indices describing temperature and rainfall extremes to assess the impact of the three SAI experiments on extreme weather in the future over SAF. The results of this study indicate that, relative to the baseline period (2010–2030), all three SAI experiments are mostly over-effective in offsetting the projected RCP8.5 increase in the frequency of hot (up to −60%) and decrease (up to +10%) in cold temperature extremes over SAF and its climatic zones. These findings suggest that SAI could cause over-cooling in SAF. However, SAI impact on precipitation extremes is less linear and varies across the country's climatic zones. For example, SAI could reinforce the projected decrease in precipitation extremes across most of SAF, although it could exacerbate heavy precipitation over the KwaZulu-Natal Coast. These findings are consistent across SAI experiments except in magnitude, as GLENS_eq and GLENS_low could cause larger decreases in precipitation extremes than GLENS. These findings imply that SAI could alleviate heat stress on human health, agriculture, and vulnerable communities while simultaneously decreasing infrastructure and crops' vulnerability to flooding. It is, however, essential to interpret these findings cautiously as they are specific to the SAI experiments and modelling settings considered in the GLENS project.
Cheng, Y., Hu, Z., & McColl, K. A. (2023). Anomalously darker land surfaces become wetter due to mesoscale circulations. Geophysical Research Letters, 50(17), e2023GL104137.
Land radiative management” (LRM)—intentionally increasing land surface albedo to reduce regional temperatures—has been proposed as a form of geoengineering. Its effects on local precipitation and soil moisture over long timescales are not well understood. We use idealized cloud-permitting simulations and a conceptual model to understand the response of precipitation and soil moisture to a mesoscale albedo anomaly at equilibrium. Initially, differential heating between a high-albedo anomaly and the lower-albedo surrounding environment drives mesoscale circulations, increasing precipitation and soil moisture in the surrounding environment. However, over time, increasing soil moisture reduces the differential heating, eliminating the mesoscale circulations. At equilibrium, the fractional increase in simulated soil moisture is up to 1.3 times the fractional increase in co-albedo (one minus albedo). Thus, LRM may increase precipitation and soil moisture in surrounding regions, enhancing evaporative cooling and spreading the benefits of LRM over a wider region than previously recognized.
Mousavi, S. V., Karami, K., Tilmes, S., Muri, H., Xia, L., & Rezaei, A. (2023). Future dust concentration over the Middle East and North Africa region under global warming and stratospheric aerosol intervention scenarios. Atmospheric Chemistry and Physics, 23(18), 10677-10695.
The Middle East and North Africa (MENA) region is the dustiest region in the world, and understanding the projected changes in the dust concentrations in the region is crucial. Stratospheric aerosol injection (SAI) geoengineering aims to reduce global warming by increasing the reflection of a small amount of the incoming solar radiation to space, hence reducing the global surface temperatures. Using the output from the Geoengineering Large Ensemble Project (GLENS), we show a reduction in the dust concentration in the MENA region under both the global warming (RCP8.5) and GLENS-SAI scenarios compared to the present-day climate. This reduction in dust over the whole MENA region is stronger under the SAI scenario, except over dust hotspots and for the dry season. In other words, in the summer, with the strongest dust events, more reduction has been projected for the global warming scenario compared to the SAI scenario. The maximum reduction in the dust concentrations in the MENA region (under both global warming and SAI) is due to the weakening of the dust hotspot emissions from the sources of the Middle East. Further analysis of the differences in the surface temperature, soil water, precipitation, leaf area index and near-surface wind speed provides some insights into the underlying physical mechanisms that determine the changes in the future dust concentrations in the MENA region. Detailed correlation analysis over dust hotspots indicates that lower future dust concentrations are controlled by lower wind speed and higher precipitation in these regions under both the RCP8.5 and SAI scenarios.
Climate Overshoot and the CARE agenda (Plan A+)
The Climate Overshoot Commission, a group of former high-level government officials including former prime ministers and environment ministers, has recently published the findings of their work in a new report. Brought together to consider the risk that we will overshoot the totemic 1.5 Celcius warming target, they lay out a comprehensive set of options…
2 days ago · 2 likes · Pete Irvine
Can we trust SRM papers? Reynolds | Reviewer 2 does geoengineering
Can we trust SRM papers? Reynolds
Reviewer 2 does geoengineering
“Jesse Reynolds shows how many SRM papers overestimate risks and underestimate benefits.
Climate Overshoot Commission's Report Unveiling - September 14, 2023, Press Conference | Climate Overshoot Commission
Solar Radiation Modification: The need for governance | C2G Carnegie Climate Governance Initiative
“Why is governance of Solar Radiation Modification needed? Whether you are for, against, or unsure, of Solar Radiation Modification comprehensive international governance is urgently needed.”
Can We Keep 1.5°C Alive? 2023 Global Youth Summit on Near-term Climate Risk & Climate Interventions | SilverLining
“SilverLining Global Young Leaders Initiative (GYLI) hosted a Global Youth Summit on Near-term Climate Risk and Climate Interventions, which took place online on 4th May.”