When the Paris climate agreement was signed in 2015, it was a milestone in taking action against climate change. It set a clear goal—to keep global average temperatures from rising above 2°C compared to pre-industrial levels—and got every country on board (including the US, which can’t leave the accord till 2020).

And, yet, despite the progress, in 2017, the United Nations said that most countries are far behind on emissions reductions. When the world set a new record high for greenhouse-gas emissions in the same year, it lent support to the belief that if more ambitious targets are not set soon, then we will cross the crucial 2°C and face climate catastrophe.

Now the EU, the third largest emitter in the world, is standing up to the challenge. Miguel Arias Cañete, the EU climate head, announced in a blog post that the bloc is aiming to cut emissions to zero by 2050. The goal already has the backing of the European Parliament, and the EU will be launching public consultations within the next few weeks.

If the EU succeeds in binding itself to the target, it could be a big deal for climate action. Though smaller countries both within the EU and outside have committed to a zero-emissions goal— the EU would be the largest emitter to commit to it. It would set a benchmark for other countries to shape their policies for such a goal. As Quartz reported previously:

The zero-emissions goal is acknowledged in Article 4 of the text of the Paris climate agreement, though it doesn’t set a date for when the world should reach that target (it does say that rich countries need to get there sooner than poor ones). Most scientists agree that the zero-emissions target date for the world as a whole should likely be early in the second half of the century.

Previously, the EU had committed to cutting emissions by up to 95% of 1990 levels by 2050. It may seem like the previous goal is quite close to zero emissions, but the task of cutting emissions gets much harder the closer you try to get to zero.

That’s because it would mean cutting all emissions in sectors that currently don’t have effective technological means to achieve it. Take aviation—we currently don’t have any viable zero-emissions planes for passenger travel. In other cases, if we do have technology to cut emissions, then it is quite expensive. Take the cement industry—it produces carbon dioxide because of the use of its raw materials (beyond fossil fuels), and the only way to reduce its emissions are through capturing the carbon dioxide and storing it underground. There are only a handful of small cement plants testing the technology and hoping they can find ways to make it cheaper for larger scale deployment.

To be sure, it’s important to clarify that the EU’s goal is to get to “net-zero” emissions. It means that, by 2050, there may still be some permissible greenhouse-gas emissions for industries or sectors that haven’t found a viable alternative. But those emissions will have to be offset through negative-emissions technology, which will require capturing carbon dioxide from the air. Unlike an electric airplane, negative-emissions technology is not fantasy. There are three companies that boast of its commercial use, but it does come at a high cost.