PARIS — Several thousand climate activists from across Europe and many from farther afield gathered peacefully near the Arc de Triomphe on Saturday to protest the outcome of the COP 21 climate conference about 12 miles away.

The demonstration was an official exception to a ban on public gatherings across France after the Paris terrorist attacks in November.

Even as the delegates at the official conference center reached a landmark accord and applauded their achievement, the crowds on the street made clear their belief that it would take much more than the measures in the deal to halt global climate change.