Climate Change

An Outbreak of Climate Optimism

But only if politicians keep their promises.


Ahead of the United Nations Climate Change Conference (COP26), the U.N. Environment Programme (UNEP) issued its Emissions Gap Report 2021, declaring that the world is on track for a global average temperature rise this century of at least 2.7°C (4.9°F). The UNEP found that the greenhouse gas (GHG) reduction pledges made by signatories to the Paris Agreement back in 2015, known as nationally determined contributions (NDCs), are far too modest to keep average temperatures from rising by less than the 2.0°C (3.6°F) threshold set by the treaty, much less the more stringent limit of 1.5°C (2.7°F), by 2100.

The UNEP report calculated that current global GHG emissions must be cut by 55 percent before 2030 in order the sustain the trajectory toward the Paris Agreement's 1.5°C goal. According to the UNEP, global GHG emissions including carbon dioxide, methane, and fluorinated gases amounted to nearly 60 gigatons in 2020. A 55 percent cut would mean lowering emissions by 33 gigatons, or 3.6 gigatons per year, until 2030.

Keep in mind that the U.S. emitted 4.6 gigatons of carbon dioxide in 2020, the lowest amount in 40 years. This is largely because of the ongoing switch from coal to lower-carbon, cheap natural gas to generate electricity, as well as the pandemic's effects on the economy and travel.

The agency found that the new and updated NDCs only take a predicted 7.5 percent off 2030 global emissions, putting the world on track for an average temperature increase of 2.7°C by 2100. The report did note that if countries' announced net-zero emissions targets were fully implemented, that could shave an extra 0.5°C off global warming, bringing the predicted temperature rise down to 2.2°C.

Now, two brand new analyses suggest that the UNEP report may be too pessimistic, largely because of new pledges made at the COP26 summit. Let's take the more optimistic one first. Yesterday, International Energy Agency (IEA) Executive Director Fatih Birol tweeted:

In mid-October, the IEA calculated in its World Energy Outlook report that if countries actually implemented their announced GHG reduction policies, then the demand for fossil fuels would peak by 2025, and annual global carbon dioxide emissions would drop by 40 percent by 2050. In that scenario, the global average temperature rise in 2100 would be around 2.1°C.

In its new quick analysis, the IEA assumes that every country that has pledged to achieve net-zero GHG emissions over the next few decades will keep its promises. It also takes into account the new agreement by 100 countries to cut methane emissions by 30 percent by 2030. "Our updated analysis of these new targets – on top of all of those made previously – shows that if they are met in full and on time, they would be enough to hold the rise in global temperatures to 1.8°C by the end of the century," notes the new IEA commentary.

Science has just published a new analysis, "Can Updated Climate Pledges Limit Warming Well Below 2°C?," parsing how the implementation of the newly announced NDCs could affect future average global temperature trends. The answer to the question posed in the article's title is "perhaps," assuming that the new pledges are fulfilled.

"We find there's a roughly one in three chance that we'll stay under 2 degrees Celsius," said lead author Yang Ou, a researcher at the Joint Global Change Research Institute, in a press release. "But even with increased ambition, we're still far away from getting down to 1.5 degrees in this century." Furthermore, the new analysis has "practically ruled out the possibility of the worst climate outcomes of 4 degrees or higher," added corresponding author Haewon McJeon, a researcher at the Department of Energy's Pacific Northwest National Laboratory.

Failures to enact and meet previous emissions pledges, as under the Kyoto Protocol, call for a bit of skepticism about these new ones. Politicians easily make promises that other leaders and future generations are supposed to keep 30 years from now.