Europe unveils a landmark law on Wednesday to achieve "climate neutrality" by 2050, under the stern gaze of teenage activist Greta Thunberg, in Brussels on a well-timed visit.

The Swedish eco-warrior, who is in the Belgian capital for a Friday protest, will attend a meeting of European Commissioners, the top EU officials who will greenlight the draft law.

Thunberg will also appear before a European Parliament committee, a visit that has angered many MEPs, as it takes place despite a ban on visitors and key staff due to the coronavirus outbreak.

According to a leaked draft seen by AFP, the proposed text aims to enshrine into law the EU's grand ambition of zero net carbon emissions by mid-century and would give the EU executive new powers to impose emission targets on member state governments.

"One of the added values is to get out of the current situation where climate objectives are taken unanimously by the European Council" which brings together heads of state and government, said French liberal MEP Pascal Canfin.

But this political shift to the commission faces almost certain opposition from the national governments and the European Parliament, both of which will have their chance to modify the law over the coming months.

"Member states and parliament will hate it," said Quentin Genard of climate think tank E3G in a blog post. "Even the more pro-European and pro-climate action countries want to keep oversight over climate policies."

'Giving up'

The ambition for climate neutrality, which would make it bind the EU's 27 member states to balance polluting emissions and removals of greenhouse gases by 2050, was approved by EU leaders at a rocky summit in June with coal-dependent Poland the only holdout.

The commission, which proposes EU law, has hailed the draft has the cornerstone of a European Green New Deal that also plans a major investment drive to decarbonise the European economy.

But, on Tuesday, Thurnberg said the widely leaked proposal does "absolutely nothing" for the climate emergency, in a joint letter with other young activists.

"Net zero emissions by 2050 for the EU equals surrender. It means giving up," the letter said.

"We don't just need goals for just 2030 or 2050. We, above all, need them for 2020 and every following month and year to come," it said.

In addition, critics say the goal depends too deeply on technology that does not exist and creates a false hope that climate change can be fixed without fundamentally changing the economy or human behaviour.

Also angering activists, the proposal steps back from the commission's original ambition to order countries to cut emissions by 50 percent or even 55 percent from 1990 levels by the end of the decade.

"With no 2030 climate target and no measures to end subsidies for fossil fuels, industrial farming and other destructive industries, the Commission has left a big hole in what's meant to be the flagship of the European Green Deal," said Sebastian Mang of Greenpeace EU.

Instead, the EU accepts that the current goal to reduce pollution by at least 40 percent by 2030 will be revised by September. 

Then, by 2023 and every five years thereafter, the EU will assess progress and possibly demand deeper emission cuts from governments in order to reach the 2050 goal.

On Tuesday, Greenpeace put pressure on the Commission by projecting on the facade of EU headquarters the image of a burning planet, framed by two messages: "The house is on fire" and "2050 is too late".