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 contribute to the goals of the agreement, countries presented comprehensive national climate change plans (national fixed contributions, NDC). These are not yet sufficient to meet the agreed temperature targets, but the agreement points to the way forward for further measures. According to the United Nations Environment Programme (UNEP), temperatures are expected to rise by 3.2oC by the end of the 21st century, based solely on the current climate commitments of the Paris Agreement. To limit the increase in global temperature to 1.5 degrees Celsius, annual emissions must be below 25 Gigaton (Gt) by 2030. With the current commitments of November 2019, emissions by 2030 will be 56 Gt CO2e, twice the environmental target. To limit the increase in global temperature to 1.5 degrees Celsius, an annual reduction in emissions of 7.6% is needed between 2020 and 2030. The four main emitters (China, the United States, the EU-27 and India) have contributed more than 55% of total emissions over the past decade, excluding emissions due to land use changes such as deforestation.
China`s emissions increased by 1.6% in 2018 to a peak of 13.7 Gt CO2 equivalent. U.S. emissions account for 13% of global emissions and emissions have increased by 2.5% in 2018. EU emissions, which account for 8.5% of global emissions, have fallen by 1% per year over the past decade. Emissions fell by 1.3% in 2018. In 2018, 7% of India`s global emissions increased by 5.5%, but its per capita emissions are one of the lowest in the G20.  Carbon dioxide, nitrous oxide and methane are gases that accumulate in the atmosphere and prevent radiation from the Earth`s surface to space, creating what is called the greenhouse effect. According to the Intergovernmental Panel on Climate Change (IPCC), the main international panel on this issue, the concentration of these thermal gases has increased significantly since pre-industrial times and has not been observed for at least 800,000 years. Carbon dioxide (the main cause of climate change) has increased by 40 per cent, nitrous oxide by 20 per cent and methane by 150 per cent since 1750, mainly due to the burning of dirty fossil fuels. The IPCC says it is “extremely likely” that these emissions have been primarily responsible for the rise in global temperatures since the 1950s.