Emissions Gap

The emissions gap measures how far projected global greenhouse gas emissions exceed the level consistent with limiting global warming to an agreed temperature goal. It is the difference, for a specified future year, between emissions expected under current policies or national pledges and emissions along pathways consistent with goals such as 1.5°C or 2°C.

What is being compared?

An emissions-gap assessment compares two estimates for the same future year. The gap therefore depends on both the policy scenario being assessed and the temperature pathway used as the benchmark.

• Projected emissions estimate what the world would emit under current policies or under full implementation of countries’ climate pledges.
• Benchmark emissions come from modelled pathways consistent with a specified temperature limit; their assumptions include the likelihood of meeting that limit and whether warming temporarily exceeds it.
• The difference is generally expressed in gigatonnes of carbon dioxide equivalent per year, allowing different greenhouse gases to be combined using a common metric.
• A larger gap means that a greater additional reduction in annual global emissions is needed to align the assessed scenario with the chosen pathway.

How it assesses climate action

The Paris Agreement seeks to hold warming well below 2°C above pre-industrial levels and pursue efforts to limit it to 1.5°C. Countries communicate their climate commitments through Nationally Determined Contributions (NDCs).

• Comparing emissions projected under NDCs with temperature-consistent pathways reveals whether the collective ambition of national pledges is sufficient.
• Comparing emissions projected under current policies with those expected under NDCs reveals an implementation gap: whether adopted policies are sufficient to deliver the pledges.
• Assessments may distinguish unconditional pledges from conditional pledges, whose fulfilment depends on specified conditions such as international finance or technological support.

What the gap does and does not tell us

The emissions gap is a measure of the adequacy of global mitigation, not a direct measurement of warming or climate damage.

• Closing the gap requires stronger emissions-reduction commitments and effective implementation across sectors.
• It differs from the remaining carbon budget, which concerns cumulative net carbon dioxide emissions compatible with a temperature limit rather than annual greenhouse gas emissions in a particular year.
• A global gap does not by itself determine each country’s fair share of reductions; that also involves equity, historical responsibility and capabilities.