In addition to crossing the 1.5-degree threshold, the limit set by the Paris Climate Agreement, by 2030, the study suggests the Earth will hit 2 degrees of warming by 2050. Earlier projections have suggested the world would reach these thresholds later, around 2035 and 2055, respectively.
Lead author James Hansen of Columbia University wrote that climatologists have overestimated the planet’s resilience to increased carbon dioxide levels. Although the United Nations’ Intergovernmental Panel on Climate Change has projected that doubling the carbon in the atmosphere would warm the planet around 3 degrees, they estimated it would be closer to 4.8 degrees. Researchers based their estimate of equilibrium climate sensitivity (ECS) on the basis of prehistoric data from sources such as ice cores.
These findings “impl[y] that there is a great amount of climate change ‘in the pipeline,’” the authors wrote. “Extraordinary actions are needed to reduce the net human-made climate forcing, as is required to reduce global warming and avoid highly undesirable consequences for humanity and nature.”
Hansen was one of the first physicists to advocate for broader governmental action to address the dangers of climate change, testifying before Congress in 1988 about its potential impacts.
The study’s conclusions came under scrutiny from some climatologists, including Michael Mann, the director of the Center for Science, Sustainability and the Media at the University of Pennsylvania.
“Jim and his co-authors are very much out of the mainstream with their newly published paper,” Mann wrote in a blog post. “That’s fine, healthy skepticism is a valuable thing in science. But the standard is high when you’re challenging the prevailing scientific understanding, and I don’t think they’ve met that standard, by a longshot.”
Specifically, Mann disputed the researchers’ conclusions on the earth’s climate sensitivity.
“[T]here is no reason that we can’t prevent dangerous levels of warming through concerted efforts to decarbonize the global economy,” he wrote. “The obstacles, at least at present, are political, not physical or even technological.”
The research comes after a summer that was the hottest on record worldwide and weeks before the beginning of the United Nations Climate Change Conference in Dubai, United Arab Emirates.