IPCC climate change report: Can we avoid 1.5°C of global warming?

The Intergovernmental Panel on Climate Change (IPCC), a global group of climate scientists, has released its latest report today. It yet again warns that without immediate and massive emissions reductions, limiting global warming to 1.5°C will be beyond reach.

“If we don’t act with the necessary speed, we will shoot past 1.5 degrees and possibly even 2 degrees,” says Peter Thorne at Maynooth University in Ireland, one of the authors of the report. “Really, it’s a call to arms.”

The world is now likely to reach 1.5°C above pre-industrial temperatures in the first half of the next decade regardless of what happens with emissions, says Thorne, but what we do now determines whether we stabilise around that threshold or blast right through it.

Does this mean the world is going to pass the 1.5°C limit?

Not necessarily, according to the authors of the report. Friederike Otto at Imperial College London says we already have all the technology needed to slash emissions. “It’s clear what needs doing and we can do it,” she says.

However, the scale of action now required is becoming ever more socially and politically unfeasible, even if it is still technically possible. Cutting emissions to half of 1990 levels by 2030 would only give us a 50 per cent chance of staying at or below the 1.5 °C target, says Chris Jones at the UK’s Met Office, another author.

“Today’s report reveals the sheer scale of the ambition required to avoid the worst consequences of climate change,” says Jones. “Current policies are not on track.”

Can we cool the world down again if we pass 1.5°C?

In theory, even if the world passes the 1.5°C mark in the coming decades, removing huge quantities of carbon dioxide from the atmosphere could cool the planet to 1.5°C by 2100, but we don’t yet have the technology.

“It is not currently considered possible to withdraw the volume of carbon dioxide needed to achieve that from the atmosphere,” Camilla Mathison at the Met Office said in a statement.

That sounds bad…

Indeed. The warming so far is already contributing to ever more extreme events – such as record-smashing heatwaves last year – and causing widespread damage and losses. The impacts will continue to worsen with every bit of extra warming, the IPCC report warns. Some of the consequences may not be reversible even if we do manage to remove enough CO2 to cool the planet later this century.

“This synthesis shows just how much the 1.1 degrees [of warming] so far is adversely affecting human and natural systems – that means, is killing people and destroying their livelihoods,” says Otto.

The report also shows the inequity of climate change, she says. “Those causing the problems are not the ones suffering the consequences.”

Hold on, what is the IPCC again?

The IPCC was set up by the UN in 1988 to review the science on climate change and how to limit it. It has done six rounds of reports since then, and this is the last part of that sixth round. We have already had the sixth-round reports on the basic science, the likely impacts of climate change and what we need to do about it, plus three special reports on the oceans, the land and on 1.5°C of warming. Today’s synthesis report combines those six reports.

Does the IPCC do its own research?

The IPCC reports are all based on previously published scientific studies. But some of those studies are done specifically for the IPCC, and the scientists who write the reports do come up with consensus estimates for things, such as how much warming there will be for a certain level of emissions. If anything, those estimates tend to be rather conservative – for instance, early IPCC reports were criticised for understating future sea level rise. There is also political wrangling over how strong the final wording is.

Political wrangling? I thought scientists write the IPCC reports?

Yes, hundreds of scientists work unpaid to review thousands of published studies and write the reports. But when it comes to the summaries for policymakers – the only parts most journalists and commentators read – the wording of every sentence is argued over by representatives from UN member states. Some major fossil fuel producers try to tone down the wording.