Despite decades of attempted progress by political means, and near unambitious agreement from scientists and world governments, the recent unilateral decision by the President of the United States to pull out of the Paris Agreement essentially proves that the democratic strategy to tackle climate change is not valid.

We the undersigned, can no longer in good conscious bring human beings into a world in which they are destined for enormous suffering. Therefore, we collectively will no longer do so, unless world leaders present a viable strategy to tackle climate change.

Even if you don't think climate change is real, it is nonetheless simply too large a risk to ignore. As best put by David Mitchell:

https://www.youtube.com/watch?v=SI5ulKiZAoE