The Paris Climate Agreement, also known as the Paris Agreement, is a legally binding international treaty signed by 195 countries in December 2015. The agreement aims to limit global warming to well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 degrees Celsius.

Under the Paris Agreement, each country must set its own targets for reducing greenhouse gas emissions and regularly report on its progress. These targets, known as nationally determined contributions (NDCs), are reviewed and updated every five years to reflect the latest scientific knowledge and technological advancements.

So, who signed the Paris Climate Agreement? All 195 countries that participated in the United Nations Framework Convention on Climate Change (UNFCCC) Conference of the Parties (COP21) in Paris signed the agreement. This includes all major emitters such as China, the United States, Russia, India, and the European Union.

The United States, under the Obama administration, was a key player in negotiating the Paris Agreement and signed it on April 22, 2016. However, in June 2017, former President Donald Trump announced that the U.S. would withdraw from the agreement, citing economic and job losses. The country officially withdrew from the agreement on November 4, 2020. However, with the inauguration of President Joe Biden, the U.S. rejoined the Paris Agreement on January 20, 2021.

Other notable countries that signed the Paris Agreement include Brazil, Canada, Japan, Mexico, and South Korea. As of 2021, all countries that signed the agreement have ratified it, except for Iran, Iraq, Libya, South Sudan, Eritrea, and Yemen.

In conclusion, the Paris Climate Agreement is a historic global effort to address the urgent threat of climate change. All 195 countries that participated in the UNFCCC COP21 signed the agreement, including major emitters like China and the United States. While the U.S. briefly withdrew from the agreement under former President Trump, it has since rejoined under President Biden. The Paris Agreement is a crucial step towards ensuring a sustainable future for our planet, and it is important that all countries continue to uphold their commitments and work towards achieving its goals.