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New research on climate change suggests that the world has already passed the point of no return of global warming.
A new paper’s model suggested that under conditions where human-made greenhouse gas emissions peaked during the 2030s and dropped to zero in 2100, global temperatures would be 3 ° C higher. warm temperatures and sea level 3 meters higher in 2500 than in 1850. Here, the Earth is seen from space. Archive image.
Photo: Unsplash / Richard Gatley
The study, published in Scientific reports – an online peer-reviewed open access scientific journal published by Nature Research – finds today that even if human-induced greenhouse gas emissions can be reduced to zero, global temperatures can continue to rise for centuries afterward.
But prominent scientists from around the world, including the head of the Victoria University of Wellington’s School of Geography, Environmental and Earth Sciences, Professor James Renwick, have already challenged the report’s conclusions.
The study authors, Jorgen Randers and Ulrich Goluke of Norwegian Business School in Oslo, used a Reduced Complexity Earth System Model (ESCIMO) to study the effect of different greenhouse gas emission reductions on changes in climate. global from 1850 to 2500 and created projections. of the increase in global temperature and sea level.
The results
“The purpose of this article is to inform that we have identified a point of no return in our ESCIMO climate model, and that it has now been left behind,” the authors said.
“At ESCIMO, the global temperature continues to rise to 2500 and above, regardless of how quickly humanity reduces man-made greenhouse gas emissions.”
Their model suggested that, under conditions where human-made greenhouse gas emissions peaked during the 2030s and dropped to zero by 2100, global temperatures would be 3 ° C warmer and the sea level 3 meters higher in 2500 than in 1850.
Under conditions where all human-generated emissions were reduced to zero during 2020, the authors estimated that after an initial decline, global temperatures would remain around 3 ° C warmer and sea levels would rise. about 2.5 meters for 2500, compared to 1850.
Global temperatures would continue to rise because melting Arctic ice and carbon-containing permafrost could increase the levels of water vapor, methane and carbon dioxide in the atmosphere.
Melting Arctic ice and permafrost would also reduce the area of ice that reflects heat and sunlight.
“This cycle appears to be triggered by global warming just + 0.5 ° C above pre-industrial level,” the authors say in their report.
The model suggested that to avoid the predicted temperature and sea level rise, all man-made greenhouse gas emissions should have been reduced to zero between 1960 and 1970.
The authors said that at least 33 gigatons of carbon dioxide would now need to be removed from the atmosphere each year beginning in 2020 through carbon capture and storage methods to prevent temperature and sea level rise from continuing once. all broadcasts have ceased.
“In other words, build 33,000 large CCS plants and keep them running forever. This is technically feasible but would be enormously expensive,” according to the report.
Results in disagreement with the understanding of the scientific community
Renwick said the results presented in the paper were interesting but contrary to the scientific community’s understanding of how the climate was changing.
“The latest round of climate modeling simulations, conducted in support of the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, shows that if greenhouse gas emissions were to stop immediately, there is likely to be very little further increase in emissions. temperatures and no sign of warming will resume in the future, “said Renwick, who was the lead author of the IPCC’s 6th Assessment Report.
Professor James Renwick.
Photo: Supplied
“If greenhouse gas emissions are reduced in accordance with the Paris Agreement, the climate would stabilize over the next century. Some things, like rising sea levels and melting ice, would continue for a longer time, but at a slower and slower rate. “
Although the title of the article implied that a complete “Earth system model” was used, the article was actually based on a “low complexity model” that captured only the broader features of the climate system, Renwick said.
The ESCIMO model has been shown to have a tendency toward “runaway” climate change in general, in part because it exaggerated the warming effect of decreasing albedo (the fraction of sunlight reflected by the earth) and the amount of greenhouse gases. greenhouse effect released by melting permafrost, he said. said.
“In summary, the results presented in this document are highly implausible and should not be viewed as a cause for alarm.”
Effective climate action by the global community in line with New Zealand’s Zero Carbon Law and the Paris Agreement would be effective in stopping climate change somewhere between 1.5 and 2 ° C warming above the pre-industrial levels, Renwick said.
“This would be associated with further increases in climate and climatic extremes that would have significant consequences for communities around the world, but there are no signs of any form of runaway climate change.”
