Paris carbon cuts are insufficient, UN report warns

Even if the 193 nations that signed the Paris climate change agreement adhere to their pledges, by 2030 their atmospheric carbon contributions will still push the global temperature 1.5 °C above the preindustrial level. That warning comes from a 3 November report by the United Nations Environment Programme (UNEP). Absent further emissions cuts, the report says, the global temperature is on course to increase by 2.9–3.4 °C by the end of the century, well exceeding the 2° threshold at which most climate scientists predict catastrophic consequences of climate change.

The stated goal of the Paris agreement, which was adopted last December and officially took effect 4 November, is to restrict temperature increases to the low end of a 1.5–2 °C range. The countries pledged that by 2030 they would limit worldwide emissions to between 54 and 56 gigatons of carbon dioxide equivalent (GtCO₂e) annually. (The world emitted 52.7 GtCO₂e in 2014.) Nations would need to cap emissions at 40–44 GtCO₂e annually by 2030 if they want to maintain a good chance of keeping temperature hikes to 2° this century, according to the UNEP. To meet that more ambitious standard, nations would have to increase their Paris emission-reduction commitments by about 25%.

Most scenarios for limiting temperatures to a 2 °C rise by 2100 assume the use of technologies for the removal of CO₂ from the atmosphere during the second half of the century. Such methods may include afforestation and reforestation, enhanced soil carbon absorption, biochar, and the combination of biomass and carbon capture and storage, the report says.

One piece of good news from the report is that emissions of CO₂ from fossil-fuel combustion and industrial activity—68% of total global greenhouse gas emissions—declined slightly for the first time in 2015, to 36.2 GtCO₂e. From 2012 to 2014, the rate of increase in CO₂ emissions had averaged 1.3% annually, down from the 2.9% average annual increase seen during the previous 12 years.