Under the 2015 Paris Agreement, countries unanimously agreed to work toward global goals that would limit global average temperature rise. Specifically, the Agreement seeks to limit the rise in the world’s average surface temperatures to “well below” 2°C above pre-industrial times this century, while “pursuing efforts” for 1.5°C. It also sets a target of eliminating global GHG emissions by the second half of the century – or at least compensating any residual emissions through, for example, forest growth.
A key principle in the Paris Agreement is that no country should backslide on its intentions, which were put forward in climate action plans known as “Nationally Determined Contributions”, or NDCs. The NDCs describe each country’s self-determined strategy for curbing GHG emissions, typically in five- or ten-year periods (i.e., currently until 2025 or 2030). Most also include plans to increase resilience. Individually, NDCs represent each country’s climate priorities and vision for achieving sustainable development. Aggregated, they represent the world’s collective efforts to fight climate change. However current NDCs are estimated to collectively result in a temperature rise of 2.9 to 3.4 degrees C by 2100[1].

All countries are expected to submit increasingly ambitious NDCs every five years, often described as a “ratchet mechanism”. A first opportunity to do so is in 2020. Achieving the Paris Agreement’s goals will require an emissions peak as soon as possible, followed by sharp reductions in GHG emissions. Therefore, many see high ambition in 2020 as fundamental to get on track to 1.5°C and counter a worrying trend of rising emissions[2]. The transformative climate action required needs a global commitment to raising ambition, articulated in the next generation of NDCs, to create economic drivers that shift investments away from fossil fuel use and carbon-intensive practices.
Furthermore, many changes have occurred since the current NDCs were prepared that may provide a strong technical and economic rationale for revising the NDC. Sectoral and market trends – for example, the dramatic fall in technology costs for renewable energy and batteries – is likely to have significant impact on the prioritization of NDC actions and/or target-setting. Countries may have improved cost estimates, or wish to highlight sustainable development benefits, such as improved health or livelihoods, while those with long-term strategies have defined a new pathway toward net-zero emissions.
In the lead-up to the UN Climate Summit, UNDP and UNFCCC released the most comprehensive review to date of global ambition. The joint report, The Heat is On, revealed:

75 countries (representing 37% of global GHG emissions) intended to raise ambition through either mitigation or adaptation or both;
37 countries (16%) intended to update information in their NDCs;
71 countries (21%, including most developed nations) were either undecided on their approach, provided no information, or were seeking support for the NDC revision process; and
14 countries (26%) had no plans to revise their current NDCs.