Geoengineering/Climate Engineering

As the study of climate engineering (CE) is an emerging field involving a wide range of disciplines, the summer schools described here aimed to bring young researchers together and help constitute a scientific community. Since Nobel Prize laureate Paul Crutzen published his controversially discussed article in 2006 calling for research into CE methods, technologies involving the "deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change" are being discussed seriously and the number of CE-studies is steadily increasing. While the first studies were carried out by atmospheric physicists, oceanographers, engineers, etc., social scientists, philosophers and ethicists have more recently begun to enter the field. The growing number of disciplines involved in researching issues related to CE resulted in the call for increased interdisciplinary cooperation. The series of three interdisciplinary summer schools on CE aimed to encoura...

Economic evaluations of solar radiation management (SRM) usually assume that the temperature will be stabilized , with no economic impacts of climate change, but with possible side-effects. We know from experiments with climate models, however, that unlike emission control the spatial and temporal distributions of temperature , precipitation and wind conditions will change. Hence, SRM may have economic consequences under a stabilization of global mean temperature even if side-effects other than those related to the climatic responses are disregarded. This paper addresses the economic impacts of implementing two SRM technologies; strato-spheric sulfur injection and marine cloud brightening. By the use of a computable general equilibrium model, we estimate the economic impacts of climatic responses based on the results from two earth system models, MPI-ESM and NorESM. We find that under a moderately increasing greenhouse-gas concentration path, RCP4.5, the economic benefits of implementing climate engineering are small, and may become negative. Global GDP increases in three of the four experiments and all experiments include regions where the benefits from climate engineering are negative.

Background. At the 2015 Paris Agreement to limit global warming to a maximum of 2 degrees, climate activists and researchers began to look for alternative measures. Climate engineering (CE) - the deliberate manipulation of the planetary environment to decelerate climate change - emerges as a possibly effective, albeit risky and conflictual, option.
Aim. This article aims both at simulating a plausible international scenario of negotiation over solar climate engineering deployment, and at utilizing the rules of Model United Nations (MUN) for collaborative learning in a university class. Furthermore, the article intends to provide a framework for simulations about CE that could easily be reproduced.
Method. MUN is an established and well-tested foundation for a simulation with students, including preparation leading up to the simulation and feedback rounds afterwards. We repeated the simulation three times, recorded the sessions as well as the debriefings, and gathered interesting insight by comparing the results.
Result. For our CE simulations, we discovered: 1. Divergent interests (e.g. global north vs global south). 2. Power struggle (e.g. role of the veto powers). 3. Scientific and political ignorance (e.g. decision-making under uncertainty). 4. Risk politics (e.g. trade-offs between climate change risks vs. CE risks).
Conclusion. MUN qualifies well for simulating a CE crisis. However, known lacks in MUN settings (like underrepresentation of non-state actors) must be discussed during the debriefing. These simulations illustrate possible future conflicts over CE without being prescriptive in any way.

Most scenarios on instruments limiting global warming in line with the 1.5 °C temperature limit of the Paris Agreement rely on overshooting the emissions threshold, thus requiring the application of negative emission technologies later on. Subsequently, the debate on carbon dioxide removal (CDR) and solar radiation management (SRM) (frequently subsumed under “geoengineering”) has been reinforced. Yet, it does not determine normatively whether those are legally valid approaches to climate protection. After taking a closer look at the scope of climate scenarios and SRM methods compiling current research and opinions on SRM, this paper analyses the feasibility of geoengineering and of SRM in particular under international law. It will be shown that from the perspective of human rights, the Paris Agreement, and precautionary principle the phasing-out of fossil fuels and the reduction in consumption of livestock products as well as nature-based approaches such as sustainable—and thus climate and biodiversity-smart—forest, peatland, and agricultural management strongly prevail before geoengineering and atmospheric SRM measures in particular. However, as all of the atmospheric SRM methods are in their development phase, governance options to effectively frame further exploration of SRM technologies are proposed, maintaining that respective technologies thus far are not a viable means of climate protection.

There is a growing literature on public surveys regarding solar geoengineering, but the spatial coverage has been mostly limited to the Western societies. However, the non-Western voices are paramount to climate engineering governance since technology's reach is global and since different cultures and socio-political backgrounds might substantively affect governance discourse. Here we report a preliminary analysis of an international webbased survey conducted in March 2016, targeting university students in Japan, Korea, Australia (OECD countries), China, India, and the Philippines (non-OECD), a diverse set of six countries in the Asia-Pacific region. Our questionnaire builds on earlier studies by Mercer et al. (2011) and Merk et al. (2015) but digs deeper into the aspect of field experimentation. The survey results show that non-OECD undergraduates tend to be more seriously concerned about climate change and open to the idea of climate engineering than OECD
counterparts. Majorities of the students believe that an international framework is needed and that scientists should openly disclose all the results of field tests, including negative ones.

There is increasing urgency for large-scale deployment of carbon-removal approaches to help avoid passing
critical climatic thresholds.Given the severe risks of many terrestrial methods at extremely large scales, there
is a compelling need to also assess the potential of marine negative-emissions technologies, such as artificial ocean alkalinization.

Many modelling studies suggest that the El Niño–Southern Oscillation (ENSO), in interaction with the tropical Pacific background climate, will change with rising atmospheric greenhouse gas concentrations. Solar geoengineering (reducing the solar flux from outer space) has been proposed as a means to counteract anthropogenic climate change. However, the effectiveness of solar geoengineering concerning a variety of aspects of Earth's climate is uncertain. Robust results are particularly challenging to obtain for ENSO because existing geoengineering simulations are too short (typically ∼ 50 years) to detect statistically significant changes in the highly variable tropical Pacific background climate. We here present results from a 1000-year-long solar-geoengineering simulation, G1, carried out with the coupled atmosphere–ocean general circulation model HadCM3L. In agreement with previous studies, reducing the solar irradiance (4 %) to offset global mean surface warming in the model more than compensates the warming in the tropical Pacific that develops in the 4 × CO2 scenario. We see an overcooling of 0.3 ∘C and a 0.23 mm d−1 (5 %) reduction in mean rainfall over the tropical Pacific relative to preindustrial conditions in the G1 simulation, owing to the different latitudinal distributions of the shortwave (solar) and longwave (CO2) forcings. The location of the Intertropical Convergence Zone (ITCZ) in the tropical Pacific, which moved 7.5∘ southwards under 4 × CO2, is restored to its preindustrial position. However, other aspects of the tropical Pacific mean climate are not reset as effectively. Relative to preindustrial conditions, in G1 the time-averaged zonal wind stress, zonal sea surface temperature (SST) gradient, and meridional SST gradient are each statistically significantly reduced by around 10 %, and the Pacific Walker Circulation (PWC) is consistently weakened, resulting in conditions conducive to increased frequency of El Niño events. The overall amplitude of ENSO strengthens by 9 %–10 % in G1, but there is a 65 % reduction in the asymmetry between cold and warm events: cold events intensify more than warm events. Notably, the frequency of extreme El Niño and La Niña events increases by ca. 60 % and 30 %, respectively, while the total number of El Niño events increases by around 10 %. All of these changes are statistically significant at either 95 or 99 % confidence level. Somewhat paradoxically, while the number of total and extreme events increases, the extreme El Niño events become weaker relative to the preindustrial state, while the extreme La Niña events become even stronger. That is, such extreme El Niño events in G1 become less intense than under preindustrial conditions but also more frequent. In contrast, extreme La Niña events become stronger in G1, which is in agreement with the general overcooling of the tropical Pacific in G1 relative to preindustrial conditions.