The Paris Agreement is an international treaty aimed at combating climate change by limiting the increase in global temperature to well below 2°C above pre-industrial levels. It was adopted by the United Nations Framework Convention on Climate Change (UNFCCC) in December 2015 and signed by 195 countries, including the United States, China, and India.

The Paris Agreement came into force on November 4, 2016, after at least 55 countries accounting for at least 55% of global greenhouse gas emissions ratified the treaty. This milestone was achieved in record time, as the agreement required only 55 countries to ratify it before it could come into force.

Since then, the Paris Agreement has been in effect, and countries have been working to implement their commitments under the treaty. The core of the agreement is the Nationally Determined Contributions (NDCs), which outline each country`s plans to reduce greenhouse gas emissions and adapt to the impacts of climate change.

The Paris Agreement is a significant step towards a more sustainable future, but its success depends on the actions of individual countries. The agreement is not legally binding, and there is no penalty for countries that fail to meet their commitments. However, the treaty includes a transparency framework that requires countries to report on their progress towards their NDCs, which can help to hold them accountable.

In 2019, the United States announced its intention to withdraw from the Paris Agreement, but the decision was reversed by President Joe Biden in January 2021. The United States has now rejoined the agreement, and many other countries have reaffirmed their commitment to it.

In conclusion, the Paris Agreement came into effect on November 4, 2016, after at least 55 countries accounting for at least 55% of global greenhouse gas emissions ratified the treaty. Since then, the agreement has been in effect, and countries have been working towards implementing their commitments under the treaty. While the Paris Agreement is not legally binding, it provides a framework for global cooperation on climate change and represents a significant step towards a more sustainable future.