ABSTRACT
The social cost of carbon dioxide (SC-CO2) measures the monetized value of the damages to society caused by an incremental metric tonne of CO2 emissions and is a key metric informing climate policy. Used by governments and other decision-makers in benefit-cost analysis for over a decade, SC-CO2 estimates draw on climate science, economics, demography and other disciplines. However, a 2017 report by the US National Academies of Sciences, Engineering, and Medicine1 (NASEM) highlighted that current SC-CO2 estimates no longer reflect the latest research. The report provided a series of recommendations for improving the scientific basis, transparency and uncertainty characterization of SC-CO2 estimates. Here we show that improved probabilistic socioeconomic projections, climate models, damage functions, and discounting methods that collectively reflect theoretically consistent valuation of risk, substantially increase estimates of the SC-CO2. Our preferred mean SC-CO2 estimate is $185 per tonne of CO2 ($44-$413 per tCO2: 5%-95% range, 2020 US dollars) at a near-term risk-free discount rate of 2%, a value 3.6 times higher than the US government's current value of $51 per tCO2. Our estimates incorporate updated scientific understanding throughout all components of SC-CO2 estimation in the new open-source Greenhouse Gas Impact Value Estimator (GIVE) model, in a manner fully responsive to the near-term NASEM recommendations. Our higher SC-CO2 values, compared with estimates currently used in policy evaluation, substantially increase the estimated benefits of greenhouse gas mitigation and thereby increase the expected net benefits of more stringent climate policies.
Subject(s)
Carbon Dioxide , Climate Models , Socioeconomic Factors , Carbon Dioxide/analysis , Carbon Dioxide/economics , Climate , Greenhouse Gases/analysis , Greenhouse Gases/economics , Uncertainty , Delay Discounting , Risk , Policy Making , Environmental PolicySubject(s)
Carbon Dioxide/adverse effects , Environmental Policy/economics , Environmental Policy/legislation & jurisprudence , Extreme Weather , Federal Government , Global Warming/legislation & jurisprudence , Global Warming/prevention & control , Social Change , Animals , Carbon Dioxide/economics , Cost-Benefit Analysis , Delay Discounting/ethics , Ecosystem , Global Warming/economics , Greenhouse Effect/economics , Greenhouse Effect/legislation & jurisprudence , Greenhouse Effect/prevention & control , Gross Domestic Product/trends , Humans , Methane/adverse effects , Methane/economics , Nitrous Oxide/adverse effects , Nitrous Oxide/economics , Research/trends , Sea Level Rise , Socioeconomic Factors , Stakeholder Participation , Uncertainty , United States , Wildfires/economicsABSTRACT
Given the widely noted increase in the warming effects of rising greenhouse gas concentrations, it has been unclear why global surface temperatures did not rise between 1998 and 2008. We find that this hiatus in warming coincides with a period of little increase in the sum of anthropogenic and natural forcings. Declining solar insolation as part of a normal eleven-year cycle, and a cyclical change from an El Nino to a La Nina dominate our measure of anthropogenic effects because rapid growth in short-lived sulfur emissions partially offsets rising greenhouse gas concentrations. As such, we find that recent global temperature records are consistent with the existing understanding of the relationship among global surface temperature, internal variability, and radiative forcing, which includes anthropogenic factors with well known warming and cooling effects.
