Coercion may prevent many transgressions but it robs even actions which are legal of a part of their beauty. Freedom may lead to many transgressions but it lends even to vices a less ignoble form.
If you are interested enough in the climate crisis to read this post, you probably know that 2 degrees Centigrade of warming (or 3.6 degrees Fahrenheit) is the widely acknowledged threshold for "dangerous" climate change.