The Paris Agreement is a legally binding international treaty on climate change that was adopted by 196 countries in 2015. The goal of the agreement is to limit global warming to below 2 degrees Celsius above pre-industrial levels, with a target of 1.5 degrees Celsius.

The Paris Agreement has been in effect since November 4, 2016, after it was ratified by at least 55 countries representing at least 55% of global greenhouse gas emissions. As of 2020, 189 countries have ratified the agreement, including the European Union.

The United States, under the Obama administration, played a key role in negotiating and signing the Paris Agreement. However, in 2017, the Trump administration announced their intention to withdraw from the agreement, citing concerns about economic competitiveness and the cost of reducing greenhouse gas emissions. The withdrawal was completed on November 4, 2020, the earliest possible date under the terms of the agreement.

Despite the withdrawal of the US, the Paris Agreement remains in effect, and other countries have reaffirmed their commitment to the agreement. In fact, many countries have increased their targets for reducing greenhouse gas emissions in order to meet the more ambitious goal of limiting global warming to 1.5 degrees Celsius.

Some notable countries that are part of the Paris Agreement include China, the world`s largest emitter of greenhouse gases, India, the third-largest emitter, and the European Union, which collectively is responsible for around 10% of global greenhouse gas emissions.

Other countries that have ratified the agreement include Australia, Canada, Japan, Mexico, Russia, and many others. In total, the 189 countries that have ratified the Paris Agreement represent around 97% of global greenhouse gas emissions.

In conclusion, the Paris Agreement is a significant international effort to tackle the issue of climate change and limit the increase in global temperature. While the withdrawal of the US is a setback, many other countries remain committed to the agreement, and there is still hope that significant progress can be made in reducing greenhouse gas emissions and protecting the planet for future generations.