The end of greenhouse gas emissions “may not stop global warming”

A scientific journal has overturned its claim that we have passed the “tipping point” and global warming cannot be stopped after British experts contested the findings.

The study states that if humans ran out of greenhouse gas emissions tomorrow we would still see global temperatures continue to rise for several centuries.

Leading Scientific Reports magazine was heavily criticized by British scientists after they released a press release titled “Ending Greenhouse Gas Emissions May Not Stop Global Warming” to publicize the paper, which is still available online.

Following the backlash, the magazine revised its press release, admitting that the prediction was based on a particular computer model and that the results should be tested on “alternative models.”

Richard Betts, a professor of climate impacts at the University of Exeter, was among those who criticized the study.

Speaking to The Times newspaper, he said: “While the press release suggests that global warming may now be unstoppable for centuries, the result of the model in this paper is not convincing as a support for that message.

“The document itself does not claim to be a real-world prediction, it just reports the behavior of a model, but the press release takes a big step forward and presents it as a prediction.

The model, which is not the one used in the main projections of the Intergovernmental Panel on Climate Change, has not proved credible enough to support confident predictions and is contradicted by more consolidated and widely evaluated data [models] in many of its physical processes.

‘This document can clearly be cited in support of a misleading message that it is now “too late” to avoid catastrophic climate change, which could potentially cause unnecessary despair.

“However, the study is nowhere near strong enough to make such a scary message believable.”

Sir Brian Hoskins, a climatologist at Imperial College London who was also not involved in the study, questioned the team’s “toy” model.

“This is the kind of investigation with a toy model that should be done and it’s fun, but it shouldn’t get this kind of publicity until the processes involved have been studied using more complex models and representations,” he said.

Andrew Watson, a Royal Society research professor at the University of Exeter, said he disagrees with the press release describing global warming as potentially catastrophic, “given it takes 500 years.”

The study authors include Professor Jorgen Randers, a respected Norwegian academic from BI Norwegian Business School in Oslo.

Professor Randers told MailOnline: ‘The way I see it, [Scientific Reports] they have published, in an extremely useful way, what we requested in our document, which is a report on what happens in the big climate models when they stop emissions in 2020 “.

However, some scientists hailed the findings as significant and noteworthy.

“This study provides evidence of what we don’t want to hear: that global warming may already have reinforced itself and that we have therefore passed the tipping point to stop climate change in the long term,” Phillip Williamson of the University of East Anglia he said.

Scientists used a computer model called ESCIMO to simulate the effect of different reductions in greenhouse gas emissions on changes in global climate between now and 2500, based on records dating back to 1850.

Even if all man-made greenhouse gas emissions were reduced to zero this year, global temperatures would still be around 5.4 ° F (3 ° C) warmer in 2500 than in 1850, the model found.

Sea level, meanwhile, would rise by about eight feet (2.5 meters) by 2500, compared with 1850, submerging glaciers and flooding lands.

“Recently, there have been warnings that some of these tipping points are approaching and are too dangerous to ignore,” say scientists from BI Norwegian Business School in Oslo in their research paper.

“In this paper we report that in the ESCIMO climate model the world has already passed a tipping point for global warming.”

The team tried another scenario, extending the date on which humanity theoretically brings greenhouse gas emissions to zero.

In this scenario, where human-made greenhouse gas emissions peak during 2030 and drop to zero by 2100, global temperatures will be 5.4 ° F (3 ° C) warmer and sea level 10 feet (three meters) 2500 taller than before. in 1850 – an even greater sea level rise.

The authors suggest that the continued melting of Arctic ice and carbon-containing permafrost – continuously frozen ground – could increase the amount of water vapor, methane and carbon dioxide in the atmosphere.

This would also reduce the area of ​​ice that reflects heat and light from the Sun, causing more shortwave radiation to be absorbed by the Earth, heating the planet.

This could mean that humanity will have to create more white buildings to reflect more sunlight into space to compensate for the loss of ice.

To prevent predicted temperature and sea level rise, the authors suggest that all man-made greenhouse gas emissions should have been reduced to zero between 1960 and 1970.

As it stands, humans will need to take proactive steps to remove at least 33 gigatons of carbon dioxide from the atmosphere each year from 2020 onwards through carbon capture and storage methods, according to the authors.

This can help limit the potentially catastrophic impacts of this on Earth’s ecosystems and human society, which may have to evacuate entire cities when sea level rise causes severe flooding.

‘The results should not be misinterpreted as saying we are doomed, with nothing that can be done to make a difference,’ said Professor Williamson.

Conversely, the differences between their scenarios – net zero by the end of the century and net zero now – are dramatic, giving the choice of climate catastrophe during our children’s lifetimes or keeping future temperature rises below. 1.5 ° C for at least a century.

Professor Mark Maslin, a climate change expert at University College London, said the findings need to be confirmed by more complex climate models used by the Intergovernmental Panel on Climate Change (IPCC).

The latest round of climate modeling simulations conducted by the IPCC shows that if greenhouse gas emissions were to cease immediately, there is likely to be a very small further rise in temperatures and no signs of warming in the future.

‘These results come from a model that has not undergone the rigorous cross-checking and testing typical of climate models,’ said Professor Maslin.

The study authors encourage other researchers to explore their findings using alternative models.