Social cost of carbon (SCC) research has paid increasing attention to climate tipping points and feedback mechanisms. The weakening of the Atlantic Meridional Overturning Circulation (AMOC) is currently treated as a global benefit, as it would lower Northern Hemisphere surface temperatures and thereby offset parts of global warming and its associated economic damages. We add to the literature on economic impacts of AMOC weakening by, for the first time, adding a second impact channel which acts through carbon cycle changes. A weaker AMOC directly leads to a reduced export of carbon-rich surface waters to the deep ocean, such that, conversely, more carbon remains in the atmosphere and acts to increase global temperatures and associated economic damages. By drawing on carbon cycle feedback and freshwater hosing experiments, we provide climate modelling evidence on the magnitude of this AMOC-induced carbon feedback, and develop an emulator with which to include these estimates into a simple integrated assessment model. Based on these IAM calculations calibrated to ESM results, we find that carbon cycle feedbacks lead to an SCC increase of around 1%, which is in the same order of magnitude as the SCC decrease caused by AMOC-induced temperature changes. Taking into account this carbon effect could thus flip the overall economic effect of AMOC weakening from a net benefit into a net cost.

How to cite: Schaumann, F. and Alastrué de Asenjo, E.: Flipping the cost of tipping? Economic impacts of reduced AMOC carbon drawdown, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6786, https://doi.org/10.5194/egusphere-egu24-6786, 2024.

As the world temperature rises, due to carbon dioxide (CO2) emissions from human economic activities, the risk of tipping points in the climate system becomes more concrete. This risk affects the social cost of carbon, that is, the marginal damage of increasing carbon emissions. In this paper, I study the relationship between the risk of tipping, optimal emissions, and the social cost of carbon. To do so, I solve a social-planner integrated model (Hambel et al., 2021), with a stylised ice-albedo feedback in the climate dynamics (Ashwin & Von Der Heydt, 2020). I model a tipping point induced by the ice–albedo feedback and study how this affects optimal abatement. The tipping point affect temperature dynamics, and as a consequence optimal emissions, in three ways. First, it introduces a non-linear increase in temperature. Second, it makes positive temperature shocks more persistent than negative ones. Third, it introduces a jump in the abatement necessary to revert temperatures to the pre-tipping-point level. I show that, in this context, it is crucial not only to quickly reachnet-zero emissions, but to also flatten the emission curve to reduce the risk of tipping

How to cite: Titton, A.: Climate Tipping Points and Optimal Emissions , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10993, https://doi.org/10.5194/egusphere-egu24-10993, 2024.

How to cite: Larsen, K., Bennedsen, M., Hillebrand, E., and Koopman, S. J.: Estimating Breakpoints between Climate States in Paleoclimate Data , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1823, https://doi.org/10.5194/egusphere-egu24-1823, 2024.

Governments worldwide are confronted with a need to curtail emissions of greenhouse gases to achieve the global climate targets outlined in the Paris Agreement. While carbon dioxide (CO₂) remains the primary greenhouse gas targeted in climate policies, it is important to address emissions of non-CO₂ forcers.

Trade-offs between CO₂ and other climate forcers are often determined based on Global Warming Potentials (GWP). An alternative approach is to use climate-economic approaches, estimating the social cost of different forcers. Here we focus particularly on aviation CO₂ emissions and contrail cirrus. Specifically, we explore how the social cost of contrail cirrus can be estimated using a revised version of the integrated assessment model DICE. We analyze contrail forcing from a flight-specific model that considers their spatio-temporal variability. Further, DICE has been revised in particular with respect to the geophysical model (being based on the emulator FaIR 2.0.0), and also with changes in the parameterization of the discounting and damage functions. Additionally, we examine how the social cost of short-lived forcers (contrail cirrus) and long-lived emissions (CO₂) is influenced by the discount rate and the future temperature pathway.

Concerning spatio-temporal variability, we observe that both energy forcing and the social cost of contrail cirrus are strongly dependent on flight specific conditions, including as a strong diurnal variability. Furthermore, we find that the comparison between the social costs of contrail cirrus and the social cost of CO₂ depends very strongly on the discount rate and the climate path the economy is following. This follows from the fact that the climate impacts of contrail cirrus are short lived, making their social cost less contingent than CO₂ on how future climate impacts are valued through the discount rate, and correspondingly less affected by the long-term changes in global mean surface temperature. 

We also explore the additional insights gained from analyzing the ratio of the social cost of contrail cirrus to the social cost of CO₂, beyond the information provided by analyzing the corresponding GWP values. Finally, the potential policy implications of the variability of the social cost of contrail cirrus are discussed.

How to cite: Johansson, D., Azar, C., Pettersson, S., and Sterner, T.: Trade-offs and Social Cost Estimates: Focus on CO2 and Contrail Cirrus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19046, https://doi.org/10.5194/egusphere-egu24-19046, 2024.

   As global temperatures continue to rise, the world faces a challenge in managing energy demand. With more frequent and severe heatwaves, the demand for cooling solutions surges, increasing electricity consumption and investments in cooling infrastructure. A growing number of researchers are focusing their efforts on comprehending the economic impacts of these shifts in energy demand. Nevertheless, many of these studies have predominantly relied on partial climatic factors, such as solely using daily mean temperature to estimate trends in cooling energy demand. Daily mean temperature, however, may not fully capture the building's thermal environment. Additionally, traditional methods, which do not comprehensively capture all relevant climatic conditions, have revealed regional variations in damage costs that may lead to biased results.

  This paper addresses three main research questions:

• What influences the economic impacts of cooling energy demand variations when including daily maximum and minimum temperatures and humidity in calculating Cooling Degree Days(CDD)?
• How much does the new Cooling Degree Days (CDD) calculation affect regional variation?
• How can the economic impacts of cooling energy demand variations be sensitive to shifts in the thermal comfort zone?

   Three CDD estimation methods were compared: 1) ASHRAE(traditional method) 2) UKMO(by daily maximum and minimum temperature), and 3) UKMO with HUMidex(adjusting temperature with relative humidity). We used three representative concentration pathways (RCP2.6, RCP4.5, RCP8.5) with four general circulation models to represent climate conditions. Using AIM/Hub, a CGE-based integrated assessment model, we estimated energy demand changes and GDP loss due to rising cooling energy investment. We assumed that these investments have constant elasticity of substitution between value added in capital, labor, and land, directly leading to GDP loss in AIM/Hub. We also simulated by adjusting the setpoint temperature in the thermal comfort zone with temperature and humidity conditions.

   Results reveal ASHRAE's higher CDD values in most regions but a comparable global GDP loss of about 0.61% by 2100 (compared to current emission trends and 2℃ goals), similar to other methods (0.55-0.57). However, regionally, ASHRAE and UKMO with HUMidex show reverse outputs. For instance, Japan, with a hot and humid summer, experiences a 1.53% GDP loss in ASHRAE but -1.01% in UKMO with HUMidex. These findings suggest less future cooling energy investment is needed in prior hot and humid regions, reducing economic impacts. Similar trends occur in most hot and humid regions, while hot and arid regions like Turkey and Australia experience opposite outcomes. Adjusting setpoint temperature shows that lifestyle change or building energy efficiency enhancement, which can affect cooling setpoint temperature, can avoid these economic impacts. However, more consideration should be needed in estimating adaptation costs for these changes.

How to cite: Choi, Y. and Park, C.: Rethinking the Economic Impact of Future Cooling Energy Demand Variations: Insights from Comprehensive Climatic Conditions on Thermal Comfort, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14787, https://doi.org/10.5194/egusphere-egu24-14787, 2024.

How to cite: Schleussner, C.-F., Schöngart, S., Schwartz, M., Schwaab, J., and Pretis, F.: Long-Term Legacy of Climate Overshoot on Economic Productivity: An Emulator-Based Modeling Approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16863, https://doi.org/10.5194/egusphere-egu24-16863, 2024.

Changes in regional climate extremes belong to the most impactful consequences of the human-induced climate crisis (Seneviratne et al. 2021). However, they are generally not or only partially considered in Integrated Assessment Models (IAMs) which are used to derive emissions scenarios underlying climate change projections. This has important implications for the assessment of plausible emissions pathways and associated policy decisions, in particular in the context of reports of the Intergovernmental Panel on Climate Change (IPCC).

Recently, new regional Earth System Model (ESM) emulators such as the Modular Earth System Model Emulator with spatially Resolved output (MESMER; Beusch et al. 2020, 2022; Quilcaille et al. 2022) and STITCHES (Tebaldi et al. 2022), have been developed to allow the emulation of regional ESM features when driven with output from global climate emulators. The resulting emulator chains (e.g. Beusch et al. 2022) can derive plausible geographically-resolved trajectories for mean and extreme climate variables associated with given IAM emission pathways. This fast computation of regional projections could help assess and increase the realism of emissions pathways from IAMs, e.g., with respect to afforestation, the implementation of bioenergy with carbon capture and storage (BECCS), or projected changes in agriculture and population.

This contribution presents a new experimental protocol (“FASTMIP”) building on global and regional ESM emulators and allowing the fast derivation of geographically-resolved climate change projections for new emissions scenarios, in coordination with other existing tools (e.g. Nicholls et al. 2020, Kikstra et al. 2022). The proposed FASTMIP experiment could help inform the choice of emission scenarios within the 7^th phase of the Coupled Model Intercomparison Project (CMIP7), and provide new insights towards to the integration of climate feedbacks in IAMs. First analyses showing the potential of the FASTMIP experiment for constraining IAM projections will be presented.

References:

Beusch, L., L. Gudmundsson, S.I. Seneviratne, 2020, Earth System Dynamics, 11, 139-​159

Beusch, L., Z. Nicholls, L. Gudmundsson, M. Hauser, M. Meinshausen, and S.I. Seneviratne, 2022, Geoscientific Model Development, 15 (5), 2085-2103, doi: 10.5194/gmd-15-2085-2022.

Kikstra, J.S., et al., 2022, Geosci. Model Dev., 15, 9075–9109.

Nicholls, Z.R.J., et al., 2020, Geosci. Model Dev., 13, 5175–5190.

Quilcaille, Y., L. Gudmundsson, L. Beusch, M. Hauser, and S.I. Seneviratne, 2022, Geophysical Research Letters, 49, e2022GL099012.

Seneviratne, S.I., X. Zhang, M. Adnan, W. Badi, C. Dereczynski, A. Di Luca, S. Ghosh, I. Iskandar, J. Kossin, S. Lewis, F. Otto, I. Pinto, M. Satoh, S.M. Vicente-Serrano, M. Wehner, and B. Zhou, 2021: Chapter 11: Weather and Climate Extreme Events in a Changing Climate. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V. et al. (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1513–1766, doi:10.1017/9781009157896.013. (https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter11.pdf)

Tebaldi, C., A. Snyder, and K. Dorheim, 2022, Earth System Dynamics, 13, 1557–1609.

How to cite: Seneviratne, S., Quilcaille, Y., Windisch, M., Gudmundsson, L., Biess, B., Jaeger, F., Hauser, M., and Hirschi, M.: Using regional ESM emulators to assess climate feedbacks to IAMs: The "FASTMIP" experimental protocol, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18731, https://doi.org/10.5194/egusphere-egu24-18731, 2024.

There is strong motivation in Integrated Assessment Modelling to generate methods for quickly approximating regional climate impacts. Here, we use climate impacts from the Inter-Sectoral Impacts Model Intercomparison Project phase 2b (ISIMIP2b) to emulate impacts based on global mean surface temperature anomaly, beginning with crop yields and extending the analysis to other sectors. Unlike many existing methods, we emulate impacts directly, rather than first emulating regional climate. We find that a second order polynomial function of global mean temperature is a very good predictor of changes in regional crop yield, in line with existing research on damage function literature. Socio-economic and other drivers must be treated with care in the process. By using multiple driving climate models and impact models that are available for many impacts in ISIMIP, we are also able to sample uncertainty in the severity in changes in impacts with increasing warming.

We built our climate impacts emulator for the 10 regions considered by the IPCC for the Sixth Assessment Working Group 3 report, but the selection of regions is flexible, and could be applied to any existing IAM. Our impacts emulator can also be used to construct updated damage functions for use in economic models and cost-benefit IAMs.

This approach will be used to generate climate impact functions within the newly created FRIDA integrated assessment model, which seeks to account for feedbacks between all components of the human-Earth system – such as the climate, food systems, and energy production – as these are key drivers of the response to anthropogenic forcing.

How to cite: Wells, C. and Smith, C.: From Global Mean Temperature to Regional Climate Impacts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1911, https://doi.org/10.5194/egusphere-egu24-1911, 2024.

Future socio-economic development plays a crucial role in both climate policy and the impacts of climate change. In this study, we for the first time systematically compare the costs of mitigation, adaptation, and residual damage for different socio-economic and climate scenarios known as the Shared Socio-economic Pathways (SSPs). For this, we combine recent damage estimates with adaptation costs and introduce differences in the effectiveness of adaptation based on the SSP projection. The results can be presented in terms of SSP/RCP matrix, with optimal climate outcomes as a function of SSP. The results can also be used to identify critical factors determining the optimal temperature, including socio-economic development, technology development and limits to mitigation and adaptation. The socio-economic limits to adaptation lead to damage costs that are 15% to 60% higher than if optimal adaptation had been possible. Overall, this study demonstrates that the socio-economic developments assumed in the SSP, including inequality reduction and institutional strength, can be equally important for the optimal outcome as the factors typically studied such as discount rate.

How to cite: van der Wijst, K.-I., Hof, A., de Bruin, K., and van Vuuren, D.: Comparing mitigation, adaptation and residual damage costs under different socio-economic and climate scenarios, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19478, https://doi.org/10.5194/egusphere-egu24-19478, 2024.