The Paris Agreement is a treaty signed by 195 countries around the world to address the global threat of climate change. 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. The Paris Agreement was adopted on December 12, 2015, and entered into force on November 4, 2016.

As of July 2021, 191 out of the 195 signatory countries have ratified the Paris Agreement and submitted their Nationally Determined Contributions (NDCs). This means that these countries have committed to taking specific actions to reduce their greenhouse gas emissions and contribute to the global effort to limit the rise in temperature.

The four countries that have not ratified the Paris Agreement are Iran, Iraq, Eritrea, and Libya. These countries have not yet submitted their NDCs, and their participation in the agreement remains uncertain.

The largest emitters of greenhouse gases, including China, the United States, and the European Union, have all ratified the Paris Agreement and submitted their NDCs. These countries have committed to significant reductions in their emissions over the coming years.

China, the world`s largest emitter of greenhouse gases, has pledged to peak its emissions by 2030 and to increase the share of non-fossil fuels in its energy mix to 20% by the same year. The United States, the second-largest emitter, has committed to reducing its emissions by 26% to 28% below 2005 levels by 2025. The European Union has set a target of reducing its emissions by at least 40% below 1990 levels by 2030.

Other countries, including India, Brazil, and Japan, have also ratified the Paris Agreement and submitted their NDCs. India, the world`s third-largest emitter, has pledged to reduce the emissions intensity of its GDP by 33% to 35% below 2005 levels by 2030. Brazil has committed to reducing its emissions by 37% below 2005 levels by 2025, while Japan has set a target of reducing its emissions by 26% below 2013 levels by 2030.

In conclusion, the ratification of the Paris Agreement by 191 countries is a significant step towards addressing the global threat of climate change. These countries have committed to taking specific actions to reduce their greenhouse gas emissions and contribute to the global effort to limit the rise in temperature. While the participation of four countries remains uncertain, the collective commitment of the international community provides hope for a sustainable future for all.