Limiting global warming to 1.5º is no longer possible: report

Limiting global warming to 1.5 degrees Celsius is no longer plausible, as shown in a new pivotal study published by the Cluster of Excellence “Climate, Climate Change and Society” (CLICCS) at the University of Hamburg

The goal of limiting this temperature was the first diagnosis of the UN Intergovernmental Panel on Climate Change, which warned that, below this temperature, the effects of global warming would not be so drastic for life and humans on Earth by the end of the century.

The irrepressible and compulsive collective human behaviour is missing out on that opportunity. For that, a “deep decarbonization” is required, which is not happening, says the study.

Limiting global warming to 1.5º

In the annual Hamburg Climate Futures Outlook report, the participating researchers systematically assessed the extent to which societal changes are already underway, while also looking at certain physical processes often discussed as tipping points.

“Actually, when it comes to climate protection, some things have already been implemented. But if you look at the development of social processes in detail, keeping global warming below 1.5 degrees is not yet plausible,” says CLICCS Professor Anita Engels.

With many efforts and a real “implementation ambition” of measures to decarbonize the energy that humans use on the planet, perhaps the elevation of no more than 2 degrees is still plausible. Therefore, efforts must focus on adaptation.

CLICCS researchers analyzed how social factors, such as fossil fuel sales, and physical factors, such as sea ice reduction, hamper the goal of limiting the global average temperature rise by 1.5 degrees Celsius relative to industrialization. The farther from the target, the less impact, and the closer, the more impact. (Photo CLICCS/Universität Hamburg)

According to the Hamburg Climate Futures Outlook, especially consumption patterns and corporate responses are slowing down urgently needed climate protection measures.

Other key factors, such as UN climate policy, legislation, climate protests, and divestment from fossil fuels, are supporting efforts to meet climate goals.

However, as the analysis shows, this positive dynamic alone will not be enough to stay within the 1.5-degree limit. “The required deep decarbonization is simply progressing too slowly,” says Engels.

Turning point

In addition, the team assesses certain physical processes that are frequently discussed as tipping points: the loss of Arctic sea ice and the melting of ice sheets are serious developments, as are regional climate changes.

But they will have very little influence on global temperature until 2050. In this sense, the thawing of the permafrost, the weakening of the Atlantic Meridional Overturning Circulation (AMOC) and the loss of the Amazon Rainforest are more important factors, albeit moderately.

The light blue color reflects carbon emissions from fossil fuels, and the dark blue color reflects carbon emissions from permafrost as well. Even after net zero emissions from fossil fuels are achieved, carbon emissions from permafrost can persist for a long time. In addition, if carbon emissions increase, the thawing of the permafrost layer can also accelerate, which can accelerate the climate crisis, which can also reduce the carbon emission budget to achieve the target of limiting 1.5℃ rise compared to industrialization. (Photo by CLICCS/Universität Hamburg)

“The fact is that these feared tipping points could drastically change the conditions for life on Earth, but they are largely irrelevant to reaching the temperature targets of the Paris Agreement,” explains Jochem Marotzke, one of the CLICCS speakers, from the Max Planck Institute for Meteorology.

Russia Ukraine crisis

The study also covers COVID-19 and the Russian invasion of Ukraine: economic reconstruction programs have reinforced reliance on fossil fuels, meaning the changes needed now are less plausible than previously assumed.

By contrast, it is not yet clear whether efforts to safeguard Europe’s energy supply and attempts by the international community to become independent of Russian gas will undermine or accelerate the long-term phase-out of fossil fuels.

Achieving deep decarbonization

“In light of these findings, we conclude that achieving deep decarbonization worldwide by 2050 is currently implausible, given the observable trajectories of social drivers.

Selected physical processes of public interest only moderately, if at all, inhibit the plausibility of reaching the Paris Agreement temperature targets, although they can substantially modify the boundary physical conditions for society.

Reaching the 1.5°C temperature target of the Paris Agreement is not plausible, but limiting global temperature rise to below 2°C may become plausible if the ambition, implementation and knowledge gaps are closed.”

Importance of “human agency”

Outlook is currently the only assessment that links analysis from the social sciences and the natural sciences in an integrated study to assess the plausibility of certain climate futures. More than 60 experts have contributed.

According to the study, the best hope for shaping a positive climate future lies in society’s ability to make fundamental changes (“human agency”).

In addition, the Outlook reveals a variety of conditions for doing so, for example, that transnational initiatives and non-governmental actors continue to support climate protection, and that protests maintain pressure on politicians.


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