On a recent summer evening in central Paris, a handful of people trickled into a trendy Brazilian bar blasting bossa nova, passed customers toasting with caipirinhas and headed for a wooden staircase in the back. They emerged into a small room featuring a table strewn with large printed cards that showed charts explaining the science behind climate change.

“Welcome,” a young man said. “We’re going to have fun.”

For the next three hours, the group used the cards to recreate the chain of global warming, frowning as they tried to understand phenomena such as radiative forcing and ocean acidification. Then, they debated limiting energy-hungry air travel and developing nuclear power.

The group was taking part in a “Climate Fresk,” a workshop run by a nonprofit of the same name, that teaches the basics of global warming and highlights possible solutions. The events have become a trendy night out in France, with more than a million participants.

The popularity of the Climate Fresks, named for the “fresco” that participants create with the cards, comes as much of Europe faces hotter summers associated with climate change. (France is expected to experience its strongest heat wave of the summer this weekend.)