On Saturday, world leaders representing nearly 200 countries reached an unprecedented deal to cut global carbon emissions. The large room erupted in cheers when the agreement was made.

After two decades of negotiations between rich and poor countries, the Paris climate deal finally lays out the need for every country to start cutting emissions. It sets an aspirational target of keeping the global temperature rise to 1.5 degrees Celsius -- a strong goal, but a very difficult one to achieve given the targets countries have laid out. 

The deal will require countries to revisit their targets every five years. Developed countries have also agreed to raise $100 billion per year to assist with climate adaptation and mitigation strategies in developing countries. (Read expert Michael Levi's analysis of everything that's in the agreement.)

Here was President Obama’s reaction:

Here's our earlier Energy Gang analysis on what brought the world to this moment: