We need to do more – Global warming is likely to exceed 1.5 degrees
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Global warming is expected to exceed the threshold set by the 2015 Paris Agreement, although it is uncertain to what extent.
Current climate pledges are insufficient to meet the goals of the 2015 Paris Agreement, and it is likely that the global Warming will exceed 1.5 degrees Celsius.
The study suggests that the only way to minimize the magnitude of this overshoot is for countries to make more ambitious climate commitments and decarbonize their economies faster. This will help reduce the time the planet spends in a warmer state.
While exceeding the 1.5-degree mark appears inevitable, the researchers outline several possible courses, some of which will shorten the exceedance period by decades. The study was recently published in the journal Nature Climate Change.
“Let’s face it. We’re going to surpass the 1.5 degree mark in the next few decades,” said corresponding author and PNNL scholar Haewon McJeon. “That means we’re going to 1.6 or 1.7 degrees or more have to go up and get it back down to 1.5, but how fast we can get it down is key.”
PNNL researchers Gokul Iyer and Yang Ou, authors of the new study, unpack their findings Image credit: Sara Levine | National Laboratory of the Pacific Northwest
Every second saved from exceeding means less time to worry about the most damaging consequences of global warming, from extreme weather conditions to sea level rise. Forgoing or delaying more ambitious goals could lead to “irreversible and detrimental consequences for human and natural systems,” said lead author Gokul Iyer, a scientist alongside McJeon at the Joint Global Change Research Institute, a partnership between PNNL and the University of Maryland.
“Acting fast means making net-zero commitments sooner, decarbonizing faster and meeting more ambitious emissions targets,” Iyer said. “Every little helps, and you need a combination of everything. But our results show that doing it early is most important. Really do it now.”
During COP26 in 2021, the same research team found that pledges updated at the time could significantly increase the chance of limiting warming to 2 degrees Celsius above pre-industrial levels. In their new work, the authors take another step in answering the question of how to move the needle from 2 to 1.5 degrees.
“The pledges for 2021 don’t add up to anywhere near 1.5 degrees – we are forced to focus on exceeding it,” said PNNL scientist Yang Ou, who co-led the study. “Here we are trying to provide scientific support to answer the question: What kind of ratchet mechanism would get us back down and below 1.5 degrees? That is the motivation behind this paper.”
The ways forward
The authors model scenarios – a total of 27 emission pathways with different ambitions – to study what degree of warming would likely follow which course of action. Basically, the authors assume that the countries will meet their emission commitments and long-term strategies as planned.
In more ambitious scenarios, the authors model how much warming will be contained as countries decarbonize faster and bring forward the dates of their net-zero promises. Their findings underscore the importance of “short-term ambitions,” which include rapid reductions in carbon emissions from all sectors of the energy system immediately and by 2030.
If countries meet their nationally determined contributions by 2030, such as meeting a 2% minimum decarbonization rate, global carbon dioxide levels would not reach net zero this century.
However, the most ambitious path outlined could lead to net-zero carbon emissions by 2057. Such a path, the authors write, is characterized by “rapid transformations across the global energy system” and the expansion of “low-carbon technologies.” such as renewable energy, nuclear power and carbon capture and storage.”
“The technologies that will help us achieve zero emissions include renewable energy, hydrogen, electric cars and so on. Of course, these are important players,” said Iyer. “Another important piece of the puzzle are the technologies that can remove carbon dioxide from the atmosphere, such as direct air capture or nature-based solutions.”
The most ambitious scenarios outlined in her work aim to illustrate the paths on offer. But the central insight remains clear in all modeled scenarios: If 1.5 degrees are to be reached again sooner after we have warmed up, more ambitious climate promises must come.
Reference: “Ratcheting of Climate Pledges Needed to Limit Peak Global Warming” by Gokul Iyer, Yang Ou, James Edmonds, Allen A. Fawcett, Nathan Hultman, James McFarland, Jay Fuhrman, Stephanie Waldhoff, and Haewon McJeon, 10 November 2022, Nature Climate change.
The study was funded by the US Environmental Protection Agency.