Irish rockers U2 kicked off their latest trek this week, launching their 18 month long U2360 World Tour in Barcelona. But it’s not without controversy: the “Get On Your Boots” outfit have come under fire from environmental groups who claim the four-piece aren’t doing enough to lower their carbon footprint.

With over 200 staff and an average of 90,000 punters heading to each of the 100 concerts announced so far, the band’s carbon footprint is huge, experts say.

Helen Roberts, a consultant with carbonfootprint.com, told the Belfast Telegraph that, “The carbon footprint generated by U2’s 44 concerts this year [alone] is equal to carbon created by the four band members travelling the 34.125 million miles from Earth to Mars in a passenger plane.

“You also have to add the carbon emissions from the same number of concerts again next year,” she continued. “Just looking at the 44 concerts this year, the band will create enough carbon to fly all 90,000 people attending one of their Wembley concerts to Dublin. To offset this year’s carbon emissions, U2 would need to plant 20,118 trees.”

U2 haven’t responded to the claims, but Roberts calling for a statement outlining the band’s offsetting plans.