Less Than 2 °C Warming by 2100 Unlikely

By Adrian E. Raftery, Alec S. Zimmer, D. Frierson, R. Startz, Peiran Liu. Nature Climate Change, 2017

643 citations recorded by the source corpus.

The recently published Intergovernmental Panel on Climate Change (IPCC) projections to 2100 give likely ranges of global temperature increase in four scenarios for population, economic growth and carbon use1. However these projections are not based on a fully statistical approach. Here we use a country-specific version of Kaya’s identity to develop a statistically-based probabilistic forecast of CO2 emissions and temperature change to 2100. Using data for 1960-2010, including the UN’s probabilistic population projections for all countries2–4, we develop a joint Bayesian hierarchical model for GDP per capita and carbon intensity. We find that the 90% interval for cumulative CO2 emissions includes the IPCC’s two middle scenarios but not the extreme ones. The likely range of global temperature increase is 2.0–4.9°C, with median 3.2°C and a 5% (1%) chance that it will be less than 2°C (1.5°C). Population growth is not a major contributing factor. Our model is not a “business as usual” scenario, but rather is based on data which already show the effect of emission mitigation policies. Achieving the goal of less than 1.5°C warming will require carbon intensity to decline much faster than in the recent past.

Subfields: Economics and Econometrics, Global and Planetary Change, Renewable Energy, Sustainability and the Environment

View Paper: https://www.semanticscholar.org/paper/e5095f3bfd9ac28282194b90b3e94dde92e6e89e

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Citations in the corpus

The contradiction of the sustainable development goals: Growth versus ecology on a finite planet (2019, background): “The Schandl et al. (2016) model implies that decoupling can be achieved at a maximum rate of 2.”
Climate Change and Psychology: Effects of Rapid Global Warming on Violence and Aggression (2019, neutral): “Scientific communities have almost universally accepted that human activity is directly responsible for the current rapid increase in average global temperature [5].”
Is the 1.5°C target possible? Exploring the three spheres of transformation (2018, background): “[38] indicates that there is only a 5% or 1% chance of reaching the Paris Agreement targets by 2100.”
IPCC baseline scenarios have over-projected CO2 emissions and economic growth (2020, background): “5 or RCP6 (generally consistent with ∼ 3 ◦ C of warming by 2100) offer more realistic baselines (see also Raftery et al 2017) 5 .”
Extreme heat waves under 1.5 °C and 2 °C global warming (2018, background): “With the current trend in greenhouse gases emissions, however, even the 2 ◦C target is considered too optimistic, even with substantial mitigation policies (Raftery et al 2017); in this case, our study is useful to identify regions where adaptation options are most strongly and urgently needed.”
The GDP-Temperature relationship: Implications for climate change damages (2021, neutral): “17 CV is implemented by dividing the historical data into training sets of early data and testing on later data.35 This is a standard and intuitive approach for evaluating the out-of-sample performance of statistical models of time series data (e.g., see Raftery et al. 2017 and Athey et al. 2019).”
Combining climate, economic, and social policy builds public support for climate action in the US (2020, background): “Yet, governments have struggled to enact climate policies at the scale of the crisis and are not on track to keep warming below 2 ◦ C (Raftery et al 2017).”