The scientist who warned the US about climate change says it’s worse than we thought. Again.

A new study published by legendary climate scientist James Hansen and a global team of researchers has found that the planet might breach the 1.5 degrees Celsius (2.7 degrees Fahrenheit) warming target by the end of the decade and surpass the 2 degrees C target by 2050. 

The new research adds to the urgency of conversations about climate change, just weeks before leaders all over the world are expected to travel to Dubai to meet for the United Nation’s annual climate change conference, COP28. 

The group’s findings were published in the journal Oxford Open Climate Change on Thursday and garnered various responses from the climate community. For context, it has taken the world more than a century to warm a little more than 1 degree C, according to NASA. 

The 1.5 degrees C target was initially established as a target in Paris in 2015 after a push by developing nations at a previous COP, to bring attention to the fact that global warming does not impact all nations equally. 

Hansen was the first to sound the alarm on climate change in 1988 in testimony to Congress. He’s been studying the issue with even more urgency ever since. 

“The 1.5-degree limit is deader than a doornail. And the 2-degree limit can be rescued only with the help of purposeful actions to affect Earth’s energy balance,” he said in a webinar.

The study’s conclusions are provocative because its estimate of a common climate metric, called climate sensitivity, is on the higher end. The metric is a calculation of how many degrees the planet would warm by if the amount of carbon dioxide was doubled from pre-industrial times — an amount that is quickly approaching. 

The conclusions of Hansen and others are not completely out of the realm of possibility though, according to Jim Kinter, a professor of climate dynamics at George Mason University in Virginia. “There’s a range of values that we see coming from different models,” said Kinter. “And his value is at the high end or above any of the models that we’ve seen before.” 

Hansen and his team’s estimate outpaces other figures, such as the one provided by the Intergovernmental Panel on Climate Change, a United Nations body dedicated to climate science. Researchers point to a few different factors, including the loss of aerosols, tiny particles of pollution which slightly cooled the planet and protected it from further warming. Additionally, the imbalance of more energy from the sun being trapped by greenhouse gasses, like carbon dioxide, has thrown off the equilibrium of energy absorbed and reflected by the planet. The earth is now absorbing more energy from the sun which, they claim, is increasing the rate that the planet warms up. 

Another prominent climate scientist, Michael E. Mann, professor of earth and environmental science at Pennsylvania State University, disputed some of the conclusions by Hansen and other researchers. In a blog post, he called their results “very much out of the mainstream.” While Hansen’s research shows that there’s a certain amount of warming locked in even after we stop emitting carbon dioxide, Mann refutes this characterization. 

One reason so many researchers disagree on the issue of when and by how much the planet will warm is because they are working off of computer models that estimate based on the data sets provided. But scientists still don’t know how every part of our planet works. 

“The Earth system is a very complicated system,” said Kinter. Those moving parts, the ocean, the atmosphere, and land, all work in tandem but since scientists don’t know exactly how everything works down to the minutiae they rely on models to fill in the gaps. 

Complicating the matter even more is the presence of the phenomenon known as El Niño, which occurs every few years and causes temperatures to increase further. 

Kinter said that because of this we might temporarily exceed the 1.5 degrees target in the near future — either next year or the following year — but it will come back down below that. The 1.5 degrees C target that the paper and most climate scientists discuss is an average, based on what the temperature is over 30 years. 

Hansen’s paper also includes policy recommendations, an unusual inclusion in most climate science papers, such as increased global cooperation, a carbon tax, and an investment in solar geoengineering, or purposefully injecting the same components from the air pollution that used to be there back into the atmosphere to cool the planet. The last point is the most contentious, as scientists disagree severely on if solar geoengineering should even be allowed as a research topic. His inclusion of those recommendations, he said, were to draw attention to the causes and urgency of the issue, as well as to motivate young people to take action. 

“Young people need to understand what they are being handed by the older generation,” said Hansen. “They’re going to actually have to affect the politics so that the special interests do not control — especially the fossil fuel industry — does not control the future.” 

This story was originally published by Grist with the headline The scientist who warned the US about climate change says it’s worse than we thought. Again. on Nov 3, 2023.