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.   Negotiators of the agreement stated that the INDCs presented at the time of the Paris conference are insufficient and found that “estimates of aggregate greenhouse gas emissions in 2025 and 2030, resulting from planned contributions at the national level, do not fall into scenarios at 2oC of the lowest cost, but lead to a projected level of 55 gigatonnes in 2030.” and acknowledges that “much greater efforts to reduce emissions will be needed to keep the global average temperature increase to less than 2 degrees Celsius, reducing emissions to 40 gigatonnes or 1.5 degrees Celsius.”  [Necessary clarifications] Funds come from a wide range of sources – public and private, bilateral, multilateral and alternative – as part of sound actions to combat climate change and transparent implementation by developing countries. 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.