Reproducing complex simulations of economic impacts of climate change with lower-cost emulators

Abstract

Abstract. Process-based models are powerful tools for simulating the economic impacts of climate change, but they are computationally expensive. In order to project climate-change impacts under various scenarios, produce probabilistic ensembles, conduct online coupled simulations, or explore pathways by numerical optimization, the computational and implementation cost of economic impact calculations should be reduced. To do so, in this study, we developed various emulators that mimic the behaviours of simulation models, namely economic models coupled with bio/physical-process-based impact models, by statistical regression techniques. Their performance was evaluated for multiple sectors and regions. Among the tested emulators, those composed of artificial neural networks, which can incorporate non-linearities and interactions between variables, performed better particularly when finer input variables were available. Although simple functional forms were effective for approximating general tendencies, complex emulators are necessary if the focus is regional or sectoral heterogeneity. Since the computational cost of the developed emulators is sufficiently small, they could be used to explore future scenarios related to climate-change policies. The findings of this study could also help researchers design their own emulators in different situations.

Uncertainty constraints on economic impact assessments of climate change simulated by an impact emulator

“…The bottom-up models tend to project smaller economic impacts compared to the top-down approaches. The behaviour of our emulator (Takakura et al 2021) is similar to the bottom-up economic impact models (Takakura et al 2019), whose projected impact is in line with many other bottom-up projections (Rose et al 2022). Thus, this study provides information on how ECs can reduce climate-related uncertainty range of economic impact projection based on bottom-up models.…”

“…We use the emulator of Takakura et al (2021) to calculate the economic impact of climate change. The original economic impact simulation, which the emulator mimics, is a global-scale, bottom-up economic impact assessment (Takakura et al 2019).…”

“…Then the emulator was validated by the cross-validation procedure, and we have confirmed that the developed emulator can reproduce the original economic simulation results in many situations. More details can be found in Takakura et al (2021). We aggregate the economic impacts in the 17 AIM regions to the world and the seven regions: Africa, Asia, Australasia, Europe, the former Soviet Union, North America and South and Central America.…”

“…To investigate uncertainty reductions in economic impact assessments in several sectors, we apply an impacts emulator recently developed by Takakura et al (2021). Since climate change will have various impacts on diverse sectors, it is not straightforward to handle these impacts.…”

“…By using temperature and precipitation simulation outputs of ESMs and an artificial-neuralnetwork-based technique, the emulator (Takakura et al 2021) can mimic the behaviours of bottom-up, process-based economic impact models (Takakura et al 2019). Unlike a simple damage function (Howard et al 2017), which typically considers only the global mean temperature, the developed emulator takes regional heterogeneity in temperature, precipitation, socioeconomic conditions, and their crossborder effects into account.…”