Peering into the emissions gap

Grantham Affiliate Dr Heather Graven gives us the lowdown on the emissions gap.

What is the emissions gap?

The international community agreed on a 2°C target for the upper limit on global average temperature rise at the Conference of the Parties to the United Nations Framework Convention on Climate Change in Cancun in 2010 (COP16). The emissions gap is the difference between pledges made this year by individual countries about their greenhouse gas emissions through 2030, and what’s needed to have a good chance of keeping global warming below the 2°C target.

How big is the gap?

The current pledges, which are called Intended Nationally Determined Contributions or INDCs, aren’t sufficient to reduce emissions and keep warming below the 2°C target. In a report published in early November, the United Nations Environment Programme concluded the INDCs will keep warming only below 3.5°C. Another group estimates the INDCs could keep warming below 2.7°C. To reach the 2°C target, CO₂ emissions must be reduced more rapidly, and reach net zero by 2060-2075.

How do we know the size of the emissions gap?

The size of the emissions gap depends on the response of the climate to greenhouse gas emissions, the sum total of all countries’ INDCs, and what happens after 2030, the end year for the INDCs. Compiling all of the INDCs is challenging because countries used various specifications for their pledges, including emissions reductions relative to different base years or to future emissions projections. Post-2030 emissions trends are critical to the emissions gap – if no further progress on the INDCs is made, then there is almost no chance of keeping warming below 2°C.

The climate is expected to warm by about 3°C if greenhouse gas concentrations reach a level that is twice as high as their natural concentrations before the Industrial Revolution. Concentrations of greenhouse gases are  influenced not only by human-induced emissions, but also by natural emissions and removal processes. For example, about 50% of our CO₂ emissions are currently being removed from the atmosphere and stored by the ocean and by plants and soils. Research I’m conducting at Imperial College London with students and colleagues is trying to understand these CO₂ uptake processes, and how they might be affected by future climate change. If the CO₂ uptake processes become less efficient, then the emissions gap will get bigger.

How can we “mind the gap”?

With more than 150 countries submitting INDCs, the international community is committed to taking action on climate change. Climate change policies on national, regional and local scales provide targets that help governments, businesses and individuals to make long-term plans, such as investments in energy infrastructure, needed to reduce emissions. Greenhouse gas emissions in 2014 grew by only 0.6%, much less than the average annual growth of 2.4% over the last decade. If this trend continues, the emissions gap could shrink in the future with new, more ambitious policies that build on this year’s INDCs.

To check on the progress toward closing the emissions gap, we need to quantify greenhouse gas emissions. Detailed calculations are made by individual countries and reported biennially to the UN. These calculations can have biases, however, as demonstrated by the intentional under-reporting of emissions by Volkswagen. Unintentional biases may also arise because emissions can be quite variable, even for similar types of activities. At Imperial, we’re researching methods for estimating emissions that use atmospheric greenhouse gas measurements from towers, aircraft and satellites. Atmospheric measurements and models can be combined with statistical methods to estimate the aggregated emissions over a specific region or the entire globe.

Find out more

See our AVOID 2 infographic on how the INDCs relate to global temperature rise