The Paris Agreement came out of the UN Conference on Climate Change and 195 countries will sign it. The intent was to foster cooperation among nations to keep temperatures from rising globally. While on the surface it seems like a real move to reduce global warming, it will only go into effect if the 55 largest countries, who produce the most pollution, actually ratify it. Both the US and China have agreed to, and that's a start, but some of the remaining nations may choose not to ratify it
In addition, there are no provisions for enforcement of the agreement. There are also no specific requirements that nations have to meet. The agreement only states that each country must make "ambitious" attempts. No definition exists in the agreement for what constitutes ambitious and no fines or punishments are contained in it for non-compliance. Many developing countries have to weigh their efforts at growing their economies against the practice of reducing emissions and this is a difficult choice for them to make.
