If you want them to listen, you should throw food at them.
At least, that is what seemed to work pretty well for the large group of lemurs we met in a French zoo.
The same might hold true for the whole world in the light of the upcoming global climate top in Paris, and that would mean a different story.
We might only listen to the desperate cry for a change in the climate policy if we have enough food, or if all our basic needs are fulfilled.
Or another analogy: not sure if all lemurs gathering in Paris are really there to listen, they might just want to get as much food out of the show as possible.
We will see what will happen in Paris. We can only hope some important measures will be taken, and that it will not end in a noisy fight for the last piece of carrot.