The 2°C warming target remains in sight
Can the 120 countries that signed the Glasgow Climate Pact keep to the pledges they made for 2100? Researchers at EPFL have developed detailed models for calculating long-term CO2 emissions-reduction trajectories and analyzing their impact on global warming. Their findings offer a glimmer of hope.
The study by EPFL’s Laboratory of Environmental and Urban Economics (LEURE) has sounded a rare note of optimism amid an otherwise bleak climate outlook. At the COP26 conference in 2021, 120 countries upgraded their 2030 targets and committed to achieving net zero between 2050 and 2070. The LEURE researchers have found that, if countries honor the medium- and long-term pledges they made in Glasgow, the global temperature rise could be held to just below 2°C by 2100.
Our aim was to analyze the climate policies of several countries, using various integrated economic models, to determine the trajectory of both CO2 emissions and global temperatures.
Scientists Marc Vielle and Sigit Perdana, climate change modeling specialists at EPFL’s School of Architecture, Civil and Environmental Engineering (ENAC), carried out the research with colleagues from other universities within a consortium set up as part of PARIS REINFORCE, an EU-funded research and innovation project. Their findings have just been published in the journal Nature Climate Change.
“Our aim was to analyze the climate policies of several countries, using various integrated economic models, to determine the trajectory of both CO2 emissions and global temperatures,” says Vielle. “The findings provide detailed, long-term forecasts to guide decision-making. As far as we know, our study is the first published multimodel assessment that takes account of recently negotiated climate pledges.”
The net-zero challenge
The team’s findings cover three scenarios. Their forecasts suggest that if countries maintain their pre-COP26 climate policies, global temperatures will increase by 2.1–2.4°C by the end of the century. Under the second scenario, which involves countries pursuing the new climate ambitions agreed in Glasgow through 2030, the temperature rise would be slightly lower, at 2.0–2.2°C. But if countries also commit their long-term net-zero pledges, the outlook is consistent with a future rise below 2°C (1.7–1.8°C). Although this third scenario is the most optimistic, global temperatures are still predicted to increase by more than the 1.5°C target. In terms of CO2 emissions, all three scenarios show levels stabilizing and then, falling in proportion to the corresponding level of ambition, starting in 2030.
The researchers reached these conclusions by using a series of models incorporating socioeconomic, regional and technology-related factors. “We looked at the steps taken in each country to limit global warming to 1.5°C by the end of the century,” says Perdana. “To make our forecasts more reliable, we also built feasibility-related uncertainties into our assumptions.” Achieving net zero will prove a huge challenge – and the path to that point will look very different from one country to the next. The EU, for instance, aims to become carbon-neutral by 2050, while China has set a target date of 2060.
Assessing transition-related risks
The team also assessed the feasibility of the scenarios described in the paper, examining a range of factors such as whether the cost and complexity of carbon storage made it impracticable, how widely renewable-energy technologies might be deployed, whether people would be willing to accept the associated costs, and how quickly building- and transportation-related energy demand could be reduced. “Another thing that makes this study unique is that we assessed the feasibility of each scenario, looking at various factors and regional differences – since different parts of the world face very different challenges,” says Vielle. “Our findings could help governments set policy priorities, such as promoting research into particular technologies or giving the organizations developing them special access to funding.”
The study shows that the world is still on track to beat the 2°C target under the most ambitious scenario. But the researchers also stress that more effort is needed to keep global warming below 1.5°C.
Dirk-Jan van de Ven, Shivika Mittal, Ajay Gambhir, Robin D. Lamboll, Haris Doukas, Sara Giarola, Adam Hawkes, Konstantinos Koasidis, Alexandre C. Köberle, Haewon McJeon, Sigit Perdana, Glen P. Peters, Joeri Rogelj, Ida Sognnaes, Marc Vielle & Alexandros Nikas, “A multimodel analysis of post-Glasgow climate targets and feasibility challenges,” Nature Climate Change, 19 May 2023