We’re set for catastrophic climate change that exceeds 2°C of global warming even with the emission cuts pledges made ahead of the Paris climate summit in December. But there’s a way out.

If the US wants to lead the world on climate change mitigation it will need to almost double its pledged greenhouse gas cuts – and many other countries will need to double their cuts in turn.

That’s the conclusion of an interactive tool that looks at ways of avoiding 2°C of warming by 2100 – agreed to be the limit beyond which warming would lead to catastrophic consequences.


At international climate negotiations, one of the big sticking points has been deciding the fairest way to share the burden of emission cuts. Rich countries want to forget about historical emissions, which they are mostly responsible for, and allocate cuts so that we all end up emitting the same amount per person.

But poorer countries say they shouldn’t be punished for the emissions that the rest of the world caused, and argue that we should all end up with an equal amount of cumulative emissions.

Fair is fair

Each country generally defines “fair” according to what will mean the least effort for them, says Malte Meinshausen at the Potsdam Institute for Climate Impact Research in Germany. Getting them all to agree on that point seems utopian, he says.

“Every country agreed to a 2°C or lower climate target, and they all make up their own story about why their own target is fair,” says Meinshausen.

But the voluntary pledges to cut national greenhouse gas emissions made ahead of December’s climate summit in Paris aren’t enough to keep warming below 2°C.

So Meinshausen and colleagues looked at what is needed to reach the target and how to get nations to agree to them, allowing for every country to define “fair” the way that burdens them the least.

The team’s imagined scenario involves one country or group of countries leading with ambitious emissions cuts, and every other country following. But each follower country interprets its fair contribution according to what costs it the least.

“If any country wants to claim to be a leader – and they all say that they’re a leader – this is now the first litmus test,” says Meinshausen.

The team also made an interactive tool that lets people see what cuts a country would need to make to be a leader, and also what every other country would need to contribute as a follower.

Worthy pledges

Are any pledges made so far worthy of a leader? “The symbolic policy of China and the US is absolutely a leader approach,” says Meinshausen. “This is an unprecedented display of leadership. But in terms of substance, the targets unfortunately do not go far enough.”

If the whole world followed the US’s definition of “fair” – the convergence to equal per capita emissions – then the current US pledge of up to 28 per cent cuts below 2005 levels by 2025 would be pretty close to getting the world to 2°C by 2100.

But that’s unlikely. To take account of other country’s views on the matter, the US would need to step up its cuts considerably – almost doubling it to cuts of 54 per cent.

To lead effective change the European Union would need to cut its emissions by 67 per cent below 1990 levels by 2030 – a big step up from its current 40 per cent pledge.

Countries that follow the leader can also be judged by the tool. If the EU became a leader, for example, then Australia would need to almost double its emission cuts just to follow. And if Australia wanted to be a leader, it would need to almost triple them.

Robyn Eckersley at the University of Melbourne in Australia says the work is useful and could encourage more collaboration between the US, EU and China. But things will never be simple, she says. “In the real world, alas, leadership does not always induce followership.”

Some countries are already recognising that strong action to reduce emissions is a catalyst for economic benefits, for example in industrial development or health impacts, says Olivia Kember at The Climate Institute, a non-profit think-tank. These countries are shifting their positions from minimising the emission reduction burden to seizing economic opportunities. Growing recognition that climate change is already imposing costs is also influencing countries’ positions, she says.

Journal reference: Nature Climate Change, DOI: 10.1038/NCLIMATE2826

Read more: “Big ideas: Climate change”

Image credit: Attila Kisbenedek/AFP/Getty