Scientists at the University of Hamburg in Germany argued Wednesday that meeting the 2015 Paris climate agreement's goal of limiting planetary heating to 1.5°C is "currently not plausible"—but warned that despairing over climate "tipping points" risks taking attention away from "the best hope for shaping a positive climate future... the ability of society to make fundamental changes."
The Hamburg Climate Futures Outlook assessed the planetary impacts of several "physical processes that are frequently discussed as tipping points." These include the melting of sea ice in the Arctic and glaciers at the North and South Poles; the weakening of the Atlantic Meridional Overturning Circulation (AMOC), the system of ocean currents that carries warm water upward into the North Atlantic; and "dieback" in the Amazon rainforest, in which rising temperatures would dry out trees and eventually change the forest landscape into a savanna, releasing billions of tons of stored carbon.
Those scenarios "are serious developments," said researchers at the university, but the melting of ice "will have very little influence on the global temperature until 2050." The weakening of AMOC and Amazon dieback will have a "moderately" greater influence on global temperatures.
"Human agency has a large potential to shape the way climate futures will evolve."
"By extrapolating current trends," reads the study, "permafrost thaw and Amazon Forest dieback are expected to release somewhat more than one year's worth of today's anthropogenic CO2 emissions between now and 2050. Thus, the contributions of these two processes to the remaining carbon budget are small. Since both will only moderately affect the global surface temperature, we deduce that they also only moderately inhibit the plausibility of attaining the Paris agreement temperature goals."
Such tipping points "could drastically change the conditions for life on Earth," but for experts, progressive politicians, and campaigners who share the goal of limiting planetary warming to 1.5°C—or as close to that as possible—"they're largely irrelevant," said Jochem Marotzke, a study co-author and professor at the university's Cluster of Excellence "Climate, Climatic Change, and Society" (CLICCS).
In other words, The Hillexplained, "Keeping global warming below 1.5°C—the goal set in the Paris agreement—is implausible for social reasons, not technical ones."
The researchers also examined 10 "drivers of social change" including media, United Nations climate policies, transnational initiatives, climate regulations, climate litigation, knowledge production, consumption patterns, corporate responses, fossil fuel divestment, and climate and social movements like the global Fridays for Future movement and Extinction Rebellion.
With fossil fuel companies continuing to make long-term investments in oil and gas extraction even as they announce pledges to reach net-zero carbon emissions, and rampant consumption of carbon-intensive goods showing no sign of slowing down, the study says, corporate responses and consumption patterns "continue to undermine the pathways to decarbonization, let alone deep decarbonization."
A number of social drivers including social movements, climate regulations, and fossil fuel divestment were found to currently "support decarbonization, but not deep decarbonization by 2050," which is needed to attain the 1.5°C goal.
"There are promising reforms underway, especially at the E.U. level," reads the report, adding that "general and ongoing public interest in and focus on climate policies" is an "enabling condition" that could help strengthen global movements and ramp up pressure on policymakers.
The researchers' assessment of the 10 social drivers demonstrates "that human agency has a large potential to shape the way climate futures will evolve," tweeted CLICCS. "However, human agency is strongly shaped by injustices and social inequalities, which inhibit social dynamics toward deep decarbonization by 2050."
The study identified how human actions can help shift the current trajectory "toward deep decarbonization," including:
- The election of governments committed to climate action in countries including Australia, Brazil, Chile, Germany, and the U.S.;
- More engagement and influence of individuals and organizations with strong and independent climate science journalism, to help support societal mobilization for climate action; and
- Proactive communication from everyone interested in a more productive public debate on climate action based on social consensus.
"In order to be equipped for a warmer world, we have to anticipate changes, get the affected parties on board, and take advantage of local knowledge," said Anita Engels of the Center for Earth System Research and Sustainability at University of Hamburg. "Instead of just reacting, we need to begin an active transformation here and now."