There’s a reason this year’s UN climate summit drew protests and disappointed many in attendance: the world is not yet on track for limiting global warming to 1.5 degrees Celsius, the target set forth during the 2015 Paris talks to avoid climate catastrophe.

Under current pledges, temperatures will rise by 2.4 degrees Celsius by the end of the century, according to Climate Action Tracker. Time is running out.

One thing is clear: No matter how much we cut emissions, we still need to remove legacy carbon dioxide from the atmosphere.

Scientists and engineers can’t turn back time, but there are tools they can use to pull planet-warming gases out of the skies and put them back underground. The question is – can they do it fast enough? This comic explains why removing CO2 from the atmosphere is a useful tool – though not a panacea.

Matteo Farinella is a neuroscientist-turned-cartoonist who uses comics to explain science. You can follow him @matteofarinella. Danielle Renwick is the editor of Nexus Media, a nonprofit climate change news service. You can follow her @daniellerenwick.