Increased carbon dioxide in the atmosphere this year will exceed key trajectories for limiting warming to 1.5°C, Britain's Met Office predicted on Friday, with researchers reaffirming that that only "drastic" emissions cuts can keep the target in sight.
Rising emissions from fossil fuels and deforestation are set to be compounded in 2024 by the cyclical El Nino weather phenomenon, which reduces the ability of tropical forests to absorb carbon.
The Met forecast this will drive a "relatively large" rise in annual average CO2 concentrations measured this year at the Mauna Loa Observatory in Hawaii -- around 2.84 parts per million (ppm) higher than in 2023.
Researchers said that will likely take the world outside the main pathways set out by the UN's Intergovernmental Panel on Climate Change (IPCC) to limit warming to 1.5°C above pre-industrial levels -- the more ambitious goal of the 2015 Paris Agreement.
"It's looking vanishingly unlikely that we'll limit warming to 1.5°C," Richard Betts, the Met Office author of the CO2 forecast, told AFP.
"Technically speaking, we could still do it if emissions were to be reduced drastically starting immediately, but the scenarios that the IPCC uses show the buildup of CO2 in the atmosphere slowing already in order to meet that target."
Scientists warn that the world is edging closer to experiencing individual years of warming of 1.5°C or more, although that would not by itself amount to a breach of the Paris target, which is measured over an average of roughly two decades.
The IPCC has already suggested that if emissions continue as they are, the world would breach 1.5°C in the early 2030s.
