World leaders are gathered in Paris this week for the UN's much-hyped COP21 climate change conference, where it is hoped that over the next 12 days they'll reach a binding agreement to reduce carbon emissions around the globe.

It's a heavy responsibility that will likely keep delegates busy with negotiations, symposiums and press conferences until the summit is over.

Should they get a chance to step outside, however, attendees may notice an unusual number of ads for the summit's corporate sponsors around Paris.

This is not by chance — nor was it done with the approval of those corporate sponsors. 

Brandalism Air France ad

(Brandalism/Revolt Design)

Approximately 600 outdoor advertising sites in the city have been covered with satirical posters bearing the names and logos of COP21 sponsors like AirFrance, Dow Chemical and GDF Suez. 

"We're sorry we got caught," reads one fake ad for Volkswagen, referring to the company's recent diesel emissions scandal (which Volkswagen rolled out an apology campaign for in Canada this week.)

Volkswagen ad Brandalism

(Brandalism/Barnbrook)

Others take aim at similarly scandal-plagued big oil companies like Shell, Total and Exxon Mobile, which was accused earlier this year of deceiving investors about its research into the effects of fossil fuels on climate change.

Shell Brandalism ad

(Brandalism/Monstfur & Simpson)

Exxon Mobil Brandalism

(Brandalism/Barnbrook)

Brandalism Louvre ad

(Brandalism/Not An Alternative)

The outdoor advertising space itself is also owned by COP21 sponsor JC Decaux, the world's largest outdoor advertising firm, according to the company.

Images of these parody ads were published in an online gallery early this week by the British anti-advertising collective Brandalism, which has taken credit for the installations.

According to a news release from the group, more than "80 renowned artists from 19 countries across the world" — some of them quite high-profile — participated in creating spoof ads for the project.

"Amidst the French state of emergency banning all public gatherings following the terrorist attacks on 13 November in Paris, the 'Brandalism' project has worked with Parisians to insert unauthorized artworks across the city that aim to highlight the links between advertising, consumerism, fossil fuel dependency and climate change," the release reads.

"By sponsoring the climate talks, major polluters such as Air France and GDF-Suez-Engie can promote themselves as part of the solution — when actually they are part of the problem,"  said Brandalism's Joe Elan in a statement. "We are taking their spaces back because we want to challenge the role advertising plays in promoting unsustainable consumerism."

Brandalism last selfie

(Brandalism/Vinz Feel Free)

Brandalism Greenwashing

(Brandalism/Eye Saw)

Brandalism TTIP

(Brandalism/NoName)

While most of the ads pictured online are meant to mock "corporate villains," some of the artists lambasted world leaders as well.

U.S. President Barack Obama, British Prime Minister David Cameron, Japanese Prime Minister Shinzo Abe, French President François Hollande and British Finance Minister George Osborne were among the representatives from more than 150 nations at the summit's opening this week.

They, along with a handful of other politicians, were all featured in Brandalism's campaign.

Brandalism Barack Obama

(Brandalism/Bill Posters)

Brandalism David Cameron

(Brandalism/Bill Posters)

Brandalism Shinzo Abe

(Brandalism/Bill Posters)

Brandalism Hollande

(Brandalism/Eubé // KC)

Brandalism George Osborne

(Brandalism/Bill Posters)

"The multinationals responsible for climate change can keep greenwashing their destructive business models, but the communities directly impacted by them are silenced," wrote Bill Posters from Brandalism of the campaign, referring to the French government's decision to ban public demonstrations in Paris following the Nov. 13 attacks.

"It's now more important than ever to call out their lies and speak truth to power," Posters continued. "We call on people to take to the streets during the COP21 to confront the fossil fuel industry. We cannot leave the climate talks in the hands of politicians and corporate lobbyists who created this mess in the first place."

The United Nations conference on climate change continues in Paris until Dec. 11.