What the U.S. is committing to as it rejoins the Paris climate accords — and why it matters

On Friday, the United States will reenter the Paris Agreement, a climate treaty dedicated to lowering greenhouse gas emissions in more than 180 countries around the world. It was originally signed and negotiated during the final years of the Obama administration, withdrawn from by President Trump in 2020, and reentered by President Biden on his first day in office.

The drafting of the agreement took place at the 21st Conference of the Parties of the United Nations Framework Convention on Climate Change, also known as COP21. The treaty was originally signed by 175 countries, and included commitments from the world's leading CO2 emitters: China, the United States and the European Union. Today, 189 parties representing 97% of global emissions have joined, according to the World Resources Institute.

The agreement's objective is to prevent the global average temperature from warming beyond a point of catastrophe, defined as "well below" a 2 degrees Celsius (3.6 degrees Fahrenheit) increase compared to pre-industrial levels. To slow the warming, countries agreed to finance programs and share resources with the goal of becoming carbon neutral by 2050.

The agreement mandates that the parties "aim to reach global peaking of greenhouse gas emissions as soon as possible." Then, by lowering emissions goals every five years, each nation is meant to decarbonize over time.

Each nation is responsible for setting their own emissions goals. The agreement also incorporates smaller nations, which are not responsible for large emissions but often feel the greatest effects of climate change, such as sea level rise.

The lack of mandated standards make the Paris Agreement unique. It was specifically designed in light of the 1997 Kyoto Protocol, which only included 36 countries, dictated goals, and ultimately failed to significantly reduce global greenhouse gas emissions.