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To answer this question, researchers must include in the same model the costs of cutting carbon emissions (mitigation), adaptation, and building climate resilience, as well as the cost of the destruction that will ensue if we do none of these things, and the residual damage that will happen even if we do. IIASA researcher Thomas Schinko led an international research team costing the potentially huge financial impacts of coastal flooding due to rising seas. The problem is that the cost of fighting coastal flooding is also high in terms of cutting emissions, and building defenses and resilient infrastructure. “Sea level rise is one of the highest climate-related risks because you have so many effects related to it, like coastal erosion, flooding, storm surges, and the intrusion of salt water into agricultural land,” says Schinko. The team used different economic models to compare two scenarios – the costs to global GDP of coastal flooding and storm surges if the world invests in capping temperature rise below 2°C; and the same costs if current policies continue and temperature rises further. At the same time, they considered the effect on GDP of building dykes along the world’s coastlines. In the first half of this century, capping temperature makes little difference to the economic burden of coastal flooding. Adaptation, however, more By Aisling Irwin Further info: Gaupp F, Hall J, Hochrainer-Stigler S, & Dadson S (2019). Changing risks of simultaneous global breadbasket failure. Nature Climate Change 10: 54-57. [pure.iiasa.ac.at/16205] Schinko T, Drouet L, Vrontisi Z, Hof AF, Hinkel J, Mochizuki J, Bosetti V, Fragkiadakis K, et al. (2020). Economy-wide effects of coastal flooding due to sea level rise: A multi-model simultaneous treatment of mitigation, adaptation, and residual impacts. Environmental Research Communications 2 (1): e015002. [pure.iiasa.ac.at/16265] Budolfson M, Dennig F, Fleurbaey M, Scovronick N, Siebert A, Spears D, & Wagner F (2019). Optimal Climate Policy and the Future of World Economic Development. The World Bank Economic Review 33 (1): 21-40. [pure.iiasa.ac.at/15327] Franziska Gaupp: gaupp@iiasa.ac.at Thomas Schinko: schinko@iiasa.ac.at Fabian Wagner: wagnerf@iiasa.ac.at than pays for itself, with GDP suffering more if we don’t adapt than if we do. The picture however changes dramatically after 2050, when strong mitigation and adaptation leave us better off economically in the decades leading up to 2100 than doing nothing. In GDP terms, it’s a global loss of 0.5% compared with 4%. “We have to think long-term but act swiftly” — Thomas Schinko “The problem with this kind of conclusion is that it assumes that the people of today care about the people of 2100. If you are short-term orientated and you say: I don’t care about climate change beyond 2050, then you have a high “discounting rate” and you are blind to the need to mitigate. If you do care about the future, then in the extreme case, what happens in 2100 has equal weight for you as what happens next year. Most people lie somewhere in between,” comments IIASA researcher Fabian Wagner. It matters because it influences political decisions about fighting climate change. Modelers can help by putting assumptions about how much the average person socially discounts the future into economic models. For example, a model could be asked what needs to be done now to ensure that the people of 2100 have sufficient food. Wagner and his team found some deficiencies in current models. Population projections, for example, have not taken account of the dawning realization that fertility is not declining as swiftly as anticipated in sub-Saharan Africa. By refining inputs such as these, the group has shown that, even to ensure a minimal level of economic welfare for the people of 2100, we need to cut our emissions far more aggressively, accelerate human and economic development, and reduce fertility levels. “If we make the demographic transition quickly,” says Wagner, “we can spend less on climate mitigation.” © Adam Islaam | IIASA and Filonov | Dreamstime 17Optionswww.iiasa.ac.at Summer 2020