Climate change: Ban fossil fuel advertising says UN chief

But a new study released today, external by a group of leading climate scientists highlighted how close the world is getting to a long-term breach of the 1.5C mark.

They estimate that from the start of 2024 the world could only emit around 200 billion more tonnes of carbon dioxide (CO2) for a 50/50 chance of keeping warming to 1.5C – down from 500 billion tonnes at the beginning of 2020.

At current rates of emissions, this “carbon budget” could be exhausted by 2029 – although the world would probably not pass the long-term 1.5C mark until a few years later, because of warming effects from greenhouse gases other than CO2.

There are uncertainties about how exactly the climate system will react to these factors, and of course whether countries make urgent cuts to emissions.

“We have a bit of control over this as a society,” says lead author Prof Piers Forster, director of the Priestley Centre for Climate Futures at the University of Leeds.

Despite the gloom, there has been some recent progress, with particularly rapid growth in renewable wind and solar electricity.

Greenhouse gas emissions are also showing signs of plateauing – but they are still at record highs.

They need to fall quickly if global targets have a chance of being met, with every fraction of a degree of warming worsening climate impacts.

“Every degree matters; every tenth of a degree matters,” says Ko Barrett, WMO Deputy Secretary General.

“The difference between 1.5C and say 2C could mean […] dire consequences, for coastal communities, for fragile ecosystems, and the biodiversity that is contained within them, and for glaciers and the frozen parts of the world.”