While the agreement has been welcomed by many, including French President Francois Hollande and UN Secretary-General Ban Ki-moon, criticism has also emerged. James Hansen, a former NASA scientist and climate change expert, expressed anger that most of the agreement is made up of „promises“ or goals, not firm commitments.  He called the Paris talks a fraud with „nothing, only promises“ and believed that only a generalized tax on CO2 emissions, which is not part of the Paris agreement, would force CO2 emissions down fast enough to avoid the worst effects of global warming.  57 Daniel Bodansky, Legal Options for U.S. Acceptance of a New Climate Agreement 14 (Center for Climate and Energy Solutions, May 2015), on www.c2es.org/docUploads/legal-options-us-acceptance-new-climate-change-agreement.pdf. 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.  10 Fiona Harvey, Paris Climate Change Agreement: The World`s Greatest Diplomatic Success, Guardian (December 14, 2015), on www.theguardian.com/environment/2015/dec/13/paris-climate-deal-cop-diplomacy-developing-united-nations. How each country is on track to meet its obligations under the Paris Agreement can be constantly monitored online (via the Climate Action Tracker  and the climate clock).
Therefore, there is disagreement as to whether – and if so, how – the many methods to stem the Kyoto era, projects and emission credits should be included in the Article 6.4 market. To ensure effective and safe participation, a comprehensive agreement on climate change must be considered fair by the countries concerned.