United Nations Framework Convention on Climate Change. Paris Agreement. Article 2(a) unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement (2015). Lenton, T.M. et al. Tipping points in the Earth`s climate system. Proc. Natl Acad. Sci. 105, 1786–1793 (2008). Dietz, S. & Stern, N.

Endogenous growth, damage convexity and climate risk: how the Nordhaus framework supports deep economies in carbon emissions. J. 125, 574-620 (2015). Finally, the international community made its own official recognition of climate change by establishing the International Committee on Climate Change in 1988. The IPCC published its first report in 1990, calling on leaders to conclude a global treaty on climate change. Lemoine, D. & Kapnick, S. A top-down approach to project the impacts of climate change on the market. NAT. Clim. Chang. 6, 51–55 (2016).

Outside of formal intergovernmental negotiations, countries, cities and regions, businesses and members of civil society around the world are taking action to accelerate cooperative climate action in support of the Paris Agreement as part of the Global Climate Change Agenda. As mentioned in the main text, the effects of future damage, which are developing according to BHM estimates, have so far been studied using predetermined scenarios of warming and economic growth. An important contribution from Ricke et al.9 notes that BHM`s estimates are associated with fairly high social costs of carbon, which could suggest that optimal policy should be strict. Burke et al.8 show that there is a large potential reduction in damage when the temperature increase is limited to 1.5°C or 2°C. Ueckerdt et al.10 also take into account the costs of mitigation in a model with exogenous economic growth and temperature change. In relation to these contributions, our method of developing a damage function from BHM estimates within an IAM makes it possible to maintain the various feedback processes between the economic and climatic mechanisms prescribed by the DICE model. The socio-economic conditions described by SSP1 and SSP2 leave enough room to aim for optimal temperatures well below 2°C by the end of the century (Fig. 6a). In contrast, the fossil development presented by SSP5 makes the success of climate policy much more difficult and implies optimal temperatures at the end of the century around 2.5°C. It brings additional health benefits, as efforts to reduce greenhouse gases can also improve air quality. Air pollution currently kills 7 million people every year. In short, the Paris Agreement may seem like a bad deal to some, but it represents a significant step forward in getting the world to take climate action.

In May, the Democratic-led House of Representatives passed its first notable climate protection bill in a decade by a majority of 231 votes to 190. It aims to prevent the United States from withdrawing from the Paris Agreement. However, after being sent back to the Republican-led Senate, it could easily be rejected. Dasgupta, P. Devaluation of climate change. J. Uncertain risk. 37, 141–169 (2008). From this updated damage function, we deduce the optimal cost-benefit climate policy, which begins in 2020. In this economically optimal scenario, mitigation is actively sought to maximize global prosperity.

We continue to assume from DICE-2013 that no significant technology with negative emissions is available during this century. We oppose optimal policy to the business-as-usual scenario (BAU), in which climate policy is lacking. We note that under these conditions, the 2°C target, as set out in the Paris Climate Agreement, provides the optimal cost-benefit trajectory by the end of this century. We observe that this observation is largely robust in the face of various uncertainties. Our results therefore call for a swift and decisive implementation of the Paris Climate Agreement. In our analyses, we take into account uncertainties in the future evolution of temperature by taking into account three alternative values of climate sensitivity at equilibrium (ESA). In addition, we subject our results to extensive robustness tests. We study the effects of uncertainties in BILI estimates regarding parameter values and model specification.

To this end, we adopt the bootstrapping approach of the original empirical study8 and deduce a corresponding set of damage functions from the resulting 1000 samples. In addition, we perform sensitivity analyses on social preferences for changes in consumption24, alternative socio-economic futures25 and mitigation costs. The calibration of these parameters is controversial in climate economics because they reflect either how decisions should be made based on ethical concerns or how decisions are actually made. Ethical considerations are reflected, for example, in an IRSTP close to zero, as it attaches similar relevance to the consumption of future generations as to the consumption of the current generation24,62. On the other hand, choosing a higher rate reflects the fact that people generally prefer to consume today rather than postpone it. Similarly, the consumer elasticity parameter can be determined either on the basis of empirical studies63 or by answering the normative question of the importance that additional consumption should have for the well-being of society64. Goulder, L. H. & Williams, R.C. The choice of the discount rate for the evaluation of the climate protection policy.

Klitoris Chang. 3, 1250024 (2012). The Katowice Package, adopted at the United Nations Climate Change Conference (COP24) in December 2018, contains common and detailed rules, procedures and guidelines that make the Paris Agreement operational. Security concerns exacerbated by climate change can exacerbate fragile situations. It is in America`s interest to achieve global emission reductions through the Paris Agreement, as this will reduce security threats abroad. Addressing climate change and helping countries put in place adaptation efforts helps maintain a stable home environment. On the other hand, enabling endemic climate change will lead to even greater climate disruptions. These disruptions can have potentially destabilizing effects such as mass migration and create more climate refugees. As one Iraq war veteran and U.S. Army Special Advisor on Energy put it, the Paris Agreement is “an important step toward improving our national security by addressing the causes, consequences, and risks associated with climate change.” Equations (11) and (12) show that both parameters influence the weight of the well-being of future generations for today`s policies.

In particular, they influence the importance of protecting against future climate impacts for today`s policies and weigh the benefits of future societies against the emission reduction costs that today`s generation would have to bear. The choice of their values is therefore crucial for the evaluation of climate policy. In addition, Gl. (12) shows that they can also influence the balance between optimal consumption and therefore indirectly optimal investments and thus modify the growth effects that are essential to our results. The resulting distribution of economically optimal temperatures in the year 2100 inherits the properties of the ECS probability distribution. As the main text also shows, higher ECS values imply a higher temperature target due to the limited room for manoeuvre to achieve lower temperatures with climate policy. In addition, the more detailed sensitivity analysis confirms that the most likely temperature targets are around 2°C. However, there is some chance, albeit very low, that the economically optimal temperature target will be significantly higher, perhaps up to 4°C. However, the probability of these high targets decreases significantly for all ECS values above 4°C. As a result, the extreme probabilities of the HIGH VALUES of SEC are transmitted to the optimal temperature distribution in the year 2100. Although based on the same data set, different model specifications can result in significant discrepancies in the estimates.

Given that claims cost estimates are of great importance to the optimal policy solution in IAM, it is not surprising that our results are sensitive to these model specifications. .