Why being an absolutist? We don’t need to convince every country. Just the top ones that drive the most consumption/pollution.

Because the top ones won't be convinced if you don't convince the others. Tragedy of the commons and all that.

In that vision we never can’t do anything because leaders needs to be leaded by others.

People do change their habits, donate, volunteer, make concessions and work hard for the good of society in its whole.

There are a number of problems that all interlock. Democracies with their relatively short election cycles will naturally find it hard to deal with problems that last much longer than those election cycles and that have the bulk of the problems downstream of us. Voters are motivated by their personal issues first, local issues second and global issues dead last. Countries are going to have to collaborate in a very strict manner in order to deal with global issues.

Throw all of those in a blender and it's easy to see why democracy and global problems are not going lead to an actual solution. Individuals are going to make some minor difference but not enough to offset the larger trends as long as it isn't a solid majority doing this.

I agree we shouldn’t count on our liberal democraties to handle that. Individuals will do the job and the majority is coming, just wait for the boomers to evade in their fantastic plastic graves.