What does resultant behavior mean

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Press release from the Potsdam Institute for Climate Impact Research (PIK)
  • Few realistic scenarios remain to limit global warming to 1.5 ° C under the Paris Agreement, according to a new study.
  • In order to achieve this ambitious climate target, all levers must be pulled in motion, some of them to a challenging extent.
  • In addition to the energy sector, these levers also include land use.
  • Unrealistically optimistic scenarios tend to overestimate the potential of carbon capture and storage, for example.


Few realistic scenarios remain to limit the temperature rise to 1.5 ° C

Of the more than 400 climate scenarios that were evaluated in the 1.5 ° C report of the Intergovernmental Panel on Climate Change, only about 50 scenarios prevent global warming from significantly exceeding 1.5 ° C. A new study shows. Of these, only about 20 make realistic assumptions about the mitigation options, for example the possible extent of CO2 extraction from the atmosphere or the possible extent of afforestation. According to the analysis, all 20 scenarios must move at least one mitigation lever to a rather "challenging" degree. Therefore, there is a high risk for the world to exceed the 1.5 ° C limit. The realistic time window for meeting this climate target from the Paris Agreement is closing very quickly.

If all levers of climate protection are pulled in motion, it might still be possible to limit global warming to 1.5 ° C. This is an important result for the heated debate on climate policy. "The emission scenarios differ in their dependence on each of the five mitigation levers we examined. But all scenarios that we consider realistic pull at least several levers into a challenging area," says lead author Lila Warszawski from the Potsdam Institute for Climate Impact Research ( PIK). "None of the realistic scenarios relies on a single silver bullet."

All realistic scenarios use all five "levers"

"The energy sector is of course the key to the 1.5 ° C target, on the one hand by reducing energy demand and on the other by decarbonising the use and generation of energy," says Warszawski. "But we cannot do without the other strategies. Removing carbon dioxide from the atmosphere and storing it underground, for example, is also proving to be almost indispensable. Land use must become a net carbon sink, for example through rewetting of peatlands or afforestation. After all, the emissions of the strong greenhouse gas methane from animal production, but also from leaks in oil and gas production, have to be reduced. That's quite a list. "

The scientists used existing research results to define the boundaries between the "reasonable", "challenging" and "speculative" use of levers up to the middle of the century. The limits quantify the range of emission reduction potentials of each aggregated lever, which result from technological, economic, social and resource-related considerations. They can then be converted into contributions to limit warming to 1.5 ° C with little or no excess temperature.

A triple challenge for humanity

"This requires an immediate acceleration in global action to reduce greenhouse gas emissions by whatever means available," says co-author Tim Lenton of the University of Exeter. “We need a sustainability revolution, similar to what the industrial revolution once did. Otherwise, those most exposed to climate change will bear the brunt of missing the 1.5 ° C target. This is a complex task for our entire society and economy - Patchwork and rhetoric will not be enough. "

"Mankind faces a threefold challenge to stabilize global warming without significantly exceeding the 1.5 ° C limit," says co-author Nebojsa Nakicenovic of the International Institute for Applied Systems Analysis, IIASA. "First, a halving of global emissions every decade, which is a Herculean effort and requires a decarbonization revolution by phasing out fossil fuels, a leap forward in efficiency and sufficiency, as well as climate-friendly behaviors and diets. Second, CO2 from the atmosphere that is truly compatible with nature to get out through afforestation and land use changes. And thirdly, the protection of the natural elements in the earth system, which already absorb half of the global emissions from the atmosphere. "

Unrealistically optimistic scenarios overestimate the potential for capturing and injecting CO2

The scenarios that are classified as unrealistically optimistic in the analysis tend most often to overestimate the potential for carbon capture and storage. Others overestimate the reduction of non-CO2 greenhouse gases such as methane. Still others make too bold assumptions about diet changes towards more plant-based foods or about limited population growth.

The authors also took a closer look at the scenarios of the International Energy Agency (IEA) from 2018 and the "Sky" scenario from the oil and gas company Shell. Both scenarios envisage that net emissions worldwide will not decrease to zero until 2070. The researchers found that they were not within the corridor of carbon dioxide emissions for the next century, which appears to offer a realistic chance of meeting the 1.5 ° C target. The Shell Sky scenario shows emission values ​​in 2030 that are significantly higher than those of the other scenarios considered in this study.

"The Shell Sky scenario has been called a castle in the air, and it is," says co-author Gail Whiteman of the University of Exeter's Business School. "From a scientific point of view, this is very clear. In business, some still like it because, compared to other scenarios, it seems to offer a relatively easy way out of the climate crisis.

Regardless of the specific climate target, rapid emission reductions are now essential

"The necessary emission reductions are difficult to achieve, technically, but also politically. They require an unprecedented innovation in lifestyles and international cooperation," says co-author Johan Rockström from PIK. "I understand anyone who thinks that we could miss the 1.5 ° C target. It is also clear that regardless of the specific climate target, the most important thing now is to implement strong emission reductions quickly. Nevertheless, I think that one Limiting the warming to 1.5 ° C is worth every effort, because this would limit the risk of giving some tipping elements in the Earth system an additional boost, such as the ice sheets or ecosystems such as the Amazon rainforest. As technical as it all sounds like, it's just about a secure climate future for everyone. "

Items: Lila Warszawski, Elmar Kriegler, Timothy M. Lenton, Owen Gaffney, Daniela Jacob, Daniel Klingenfeld, Ryu Koide, María Máñez Costa, Dirk Messner, Nebojsa Nakicenovic, Hans Joachim Schellnhuber, Peter Schlosser, Kazuhiko Takeuchi, Sander van der Leeuw, Gail Whiteman , Johan Rockström (2021): All options, not silver bullets, needed to limit global warming to 1.5 ° C: a scenario appraisal. Environmental Research Letters [DOI: 10.1088 / 1748-9326 / abfeec]

Web link to the article: https://iopscience.iop.org/article/10.1088/1748-9326/abfeec