(a) to keep the global average temperature increase well below 2 degrees Celsius above pre-industrial levels and to continue efforts to limit the increase in temperature to 1.5 degrees Celsius above pre-industrial levels, the potential to significantly reduce the risks and effects of climate change; The Katowice package adopted at the United Nations Climate Change Conference (COP24) in December 2018 contains common and detailed rules, procedures and guidelines that affect the Paris agreement in the operation. The agreement stated that it would only enter into force (and therefore fully effective) if 55 countries that produce at least 55% of global greenhouse gas emissions (according to a list drawn up in 2015)  ratify, accept, approve or adhere to the agreement.   On April 1, 2016, the United States and China, which together account for nearly 40% of global emissions, issued a joint statement confirming that the two countries would sign the Paris climate agreement.  175 contracting parties (174 states and the European Union) signed the agreement on the first day of its signing.   On the same day, more than 20 countries announced plans to join the accession as soon as possible in 2016. The ratification by the European Union has achieved a sufficient number of contracting parties to enter into force on 4 November 2016. To combat climate change and its negative effects, 197 countries adopted the Paris Agreement at COP21 on 12 December 2015 in Paris. The agreement, which came into force less than a year later, aims to significantly reduce global greenhouse gas emissions and limit global temperature rise to 2 degrees Celsius this century, while continuing to limit the rise to 1.5 degrees. On August 4, 2017, the Trump administration officially announced to the United Nations that the United States intends to withdraw from the Paris Agreement as soon as it is legally entitled to it.  The formal declaration of resignation could not be submitted until after the agreement for the United States came into force on November 4, 2019 for a three-year date.
  On November 4, 2019, the U.S. government filed the withdrawal notice with the Secretary-General of the United Nations, custodian of the agreement, and formally withdrew from the Paris Agreement a year later, when the withdrawal came into effect.  After the November 2020 elections, President-elect Joe Biden promised to reinstate the United States in the Paris Agreement for his first day in office and renew the U.S. commitment to climate change mitigation.   The Paris Agreement is the world`s first comprehensive climate agreement.  In order to contribute to the objectives of the agreement, countries presented comprehensive national plans to combat climate change (nationally defined contributions, NDC). These are not yet sufficient to meet the agreed temperature targets, but the agreement points to the way forward for further measures. In the end, all parties recognized the need to "prevent, minimize and address losses and damages," but in particular any mention of compensation or liability is excluded.  The Convention also takes up the Warsaw International Loss and Damage Mechanism, an institution that will attempt to answer questions about how to classify, address and co-responsible losses.  COP21: The key points of the Paris agreement on the website of the Department of Europe and Foreign Affairs President Obama was able to formalize the United States in the agreement under international law by executive measures, as it does not impose new legal obligations for the country.
The United States already has a number of instruments on the books, under laws already passed by Congress to reduce carbon pollution. The country officially joined the agreement in September 2016, after submitting its request for participation.