Leading climate scientists warn that the 1.5C temperature limit, which will be discussed at crucial meetings this weekend by world leaders, is not a political construct that can easily be negotiated over.
Over the next four days, world leaders will meet in Rome and Glasgow to discuss a common approach to limit global temperature rises above 1.5C. This is the lower limit of the two set forth in the 2015 Paris climate accord.
Some countries, however, are reluctant to link their emission plans to a more difficult goal because it would require greater efforts. They prefer long-term goals like net zero by 2050.
Johan Rockstrm is the director of Potsdam Institute for Climate Impact Research, and one of the most respected climate scientists in the world. He warned that 1.5C was not like other political negotiations which can be negotiated or compromised upon.
1.5C does not represent an arbitrary number and it is not political. He said that it is a global boundary in an interview with the Guardian. Each degree is dangerous.
He stated that allowing temperatures to rise more than 1.5C would greatly increase the likelihood of irreversible climate changes. It would increase the chance of the Arctic losing its summer-ice. This could have dire consequences for the rest of climate, as the heat absorbed by the water increases, causing a feedback loop that could quickly raise temperatures.
The melting of the Greenland Ice Sheet could cause sea level rises.
An increase of 1.5C could also put at risk the Gulf Stream. This could lead to irreversible changes. It could cause catastrophe for biodiversity hotspots and damage agriculture across large swathes around the globe.
This is science, it is a number. We can now say with high confidence that 1.5C indicates a limit on the amount of warming the planet can absorb.
Rockstrm said: [Staying within] 1.5C can be achieved. This is what we should strive for.
On Saturday, the leaders of G20, the group representing the largest developed and developing economies in the world, will meet in Rome. They will fly to Glasgow on Monday morning and will be joined by over 100 other leaders from around the globe for UN Cop26's climate summit.
As the host of Cop26, the UK has established the goal of keeping 1.5C alive. However, some countries, including Russia, China, Saudi Arabia, and Saudi Arabia, have been reluctant about focusing on the 1.5C limit. They prefer to remind the world that the Paris Agreement states that temperatures must remain below 2C, while striving to keep within 1.5C.
But, scientists have shown that even if temperatures rise more than 1.5C, it will cause severe damage and some irreversible consequences.
Rockstrms was echoed by other top climate scientists. Professor of Earth systems science at University College London Mark Maslin stated that the 2018 report by the Intergovernmental Panel on Climate Change, (IPCC), made it clear that there are major climate impacts around the globe, even if global warming is limited to 1.5C.
This report also revealed that there are significant increases in impacts and damages if this target is not met. These results were supported fully by the 2021 IPCC science reports [published August]. This is the science. The Paris Agreement climate targets are non-negotiable. They have been accepted by all 197 UN member countries.
Joeri Rogelj is the director of research at Imperial College London's Grantham Institute. She stated that science shows that climate change risks rise rapidly with increasing temperatures of 1.5C to 2C. If you look at the past years, when we have experienced some of the effects of a 1.2C warming world (such as heatwaves and flooding), it would be difficult to say that this is safe.
