Every year, the UN Environment Programme (UNEP) brings together scientists from around the world to measure the size of the greenhouse gas (GHG) “emissions gap,” the difference between the emissions level countries have pledged to achieve under international agreements and the level consistent with limiting warming to well below 2 degrees C (3.6 degrees F). That benchmark exists because warming above 1.5-2 degrees C would bring increasingly catastrophic impacts. (Learn more in our post describing the world’s “carbon budget.”)
In 2016, global GHG emissions were about 52 gigatonnes (Gt CO2e/year). Total global GHG emissions have roughly doubled since 1970, and have grown dramatically even since 2000. Carbon dioxide emissions from fossil fuel combustion, cement and other processes contribute the most, around 70 percent of the total.
Encouragingly, the growth in global emissions in 2015 and 2016 is the slowest since the early 1990s (except years of global economic recession), and global CO2 emissions from fossil fuel use and cement production remained stable in both 2015 and 2016. However, it remains to be seen whether these trends will be permanent.
2. The world's largest emitters are collectively on track to achieve their promised emissions reductions for 2020, but several countries need to step up.
In 2009 and 2010, 73 Parties to the UN Framework Convention on Climate Change (UNFCCC) made GHG emissions pledges for 2020. For the G20 countries – responsible for roughly three quarters of global emissions – the Gap Report compares their projected 2020 emissions with their pledges. It found that seven G20 members (Australia, Brazil, China, the EU, India, Japan and Russia) are on track to meet their 2020 pledges; five (Canada, Mexico, the Republic of Korea, South Africa and the United States) are likely to require further action or will have to purchase offsets; and the remaining three (Argentina, Saudi Arabia and Turkey) did not make pledges for 2020. While not all members are on track to meet their pledges, collectively, 2020 emissions are expected to fall within the pledged range.
3. To keep warming between 1.5 and 2 degrees C, emissions in 2030 need to be far lower than they are expected to be.
To measure the size of the emissions gap, experts review available scenarios from the scientific literature showing how emissions must be reduced in order to limit warming to 2 and 1.5 degrees C, the temperature goals laid out in the international Paris Agreement on climate change. The experts compare these ranges against those that would be achieved under the pledges made by 166 Parties under the Paris Agreement, and against the emissions expected to occur if current policies continue (without being strengthened in order to meet the pledges). They find that a significant gap remains between Paris Agreement-compatible emissions in 2030 and both of those scenarios.
Using a benchmark of a likely chance of 2 degrees C, the gap between the Paris goals and the pledges is 11-13.5GtCO2e. Using a benchmark of a median or likely chance of 1.5 degrees C, the gap is 16-19GtCO2e. The gap between the Paris temperature goals and the current policy scenario is higher still, given that many countries are not yet on track to achieve their emissions-reduction pledges, but this is to be expected given that pledges extending to 2030 are still fairly new.
4. Existing solutions can close the gap, if they are embraced quickly.
The report finds that proven technologies, even with conservative assumptions, could reduce emissions 33 Gt CO2e/year by 2030. And if you add in newer technologies, that potential grows to 38 Gt CO2e/year in 2030. That’s more than what’s needed to close the emissions gap and keep warming below 1.5 degrees C.
More than half of this potential is from a handful of categories—solar and wind energy, efficient passenger cars, afforestation and halting deforestation—and requires quickly reducing reliance on, and soon phasing out, coal-fired power not equipped with carbon capture and storage.
5. Limiting warming to 1.5-2 degrees C also relies on carbon dioxide removal and negative emissions approaches.
The report notes that the rate at which we are depleting the carbon budget will force us to increasingly rely upon carbon dioxide removal technologies and approaches, which remove and sequester carbon dioxide. There are significant risks, however, associated with these technologies and approaches, including uncertainty in their carbon retention, the consequences of large-scale deployment, and costs and feasibility.
Scenarios that meet the 1.5 degrees C target in 2100 assume large-scale availability of negative emissions technologies, such as bioenergy combined with carbon capture and storage. These technologies would be scaled up quickly. By 2100, the average removal of carbon dioxide through negative emissions technologies would be 810 GtCO2e, which is equal to almost two decades' worth of global emissions at current rates. Few scenarios can also meet the 2 degrees C target without using negative emissions technologies.
If such technologies cannot be deployed at these rates and scale, which has yet to be proven, then our ability to meet these temperature targets is significantly compromised.
Closing the Gap
The Emissions Gap Report once again underscores the urgency of redoubling our efforts to reduce emissions. It shows that solutions exist, and if they are adopted quickly we can turn our current situation around. But with each year we wait – and with each further installment of the UNEP Emissions Gap Report – we make our ability to limit dangerous climate change more difficult, risky and costly.