A group of researchers led by International Institute for Applied Systems Analysis has used new modelling scenarios to showcase several ways with which to limit global temperature rise to 1.5°C by 2100.
According to their research, “Scenarios towards limiting global mean temperature increase below 1.5 °C“, published in the journal Nature Climate Change, there are in fact several ways to limit global warming to the Paris Agreement’s goal of 1.5°C by 2100, but their modelling shows that the right circumstances are necessary. The research represents one of the first times that scientists investigating limiting global warming to 1.5°C by 2100 have also looked at how socioeconomic conditions such as inequalities, energy demand, and international cooperation would contribute to the feasibility of achieving those goals.
The new research is based on six integrated assessment models and a simple climate model, run under different socio-economic, technological, and resource assumptions that stem from five Shared Socio-economic Pathways (SSPs). The SSPs were previously developed by the International Institute for Applied Systems Analysis (IIASA) along with key partners, and provide a look at different ways in which the world and society might progress. They include a scenario in which the world pursues sustainability, another scenario in which economic and population growth continues along business-as-usual pathways, and another in which the world focuses instead on high economic growth over sustainability.
The researchers showed that not all of these Pathways can limit global warming to 1.5°C by 2100, but did show (unsurprisingly) that all of the successfully modelled scenarios included a rapid shift away from the use of fossil fuels and towards low-carbon energy sources, lowered energy use, and the removal of CO2.
Meanwhile, barriers to achieving a 1.5°C limit to global warming included strong social and economic inequalities, continued reliance on fossil fuels, and unambitious short-term climate policies.
“A critical value of the paper is the use of the SSPs, which has helped to systematically explore conditions under which such extreme low targets might become attainable,” said IIASA Energy Program Director and coauthor Keywan Riahi. “Our assessment shows particularly the enormous value of pursuing sustainable development for reaching extreme low climate change targets. On the other hand, fragmentation and pronounced inequalities will likely come hand-in-hand with low levels of innovation and productivity, and thus may push the 1.5°C target out of reach.”
According to the research, successful scenarios saw greenhouse gas emissions peak and already begin to decline by 2030, continuing to decrease over the next two to three decades at which point zero net greenhouse gas emissions are reached between 2055 and 2075. The successful scenarios also limited energy demand by improving energy efficiency measures. Bioenergy and renewable energy technologies must scale up dramatically over the coming decades, making up at least 60% of electricity generation by 2050. Coal use must fall to less than 20% of its current levels by 2040 and oil is phased out by 2060.
“One of the goals of the Paris Agreement is to limit warming to 1.5°C, but scientific studies mainly looked at the question of limiting warming to 2°C,” said Joeri Rogelj, IIASA researcher and lead author of the study. “This study now fills this gap and explores how climate change by the end of the 21st century can be brought in line with 1.5°C of warming. Individual studies have looked at this question in the past, but this study is the first to use a broad and diverse set of models.”
The successful 1.5°C pathways are now intended for use by the wider climate change research community to be run on the most complex coupled climate models, and will serve as a starting point for further research.
“The study provides decision makers and the public with key information about some of the enabling conditions to achieve such stringent levels of climate protection,” added Rogelj.