Last Year Carbon Dioxide Levels Rose by a Record Amount

Carbon dioxide is accumulating in the atmosphere faster than ever before, putting hopes of limiting warming in jeopardy.

Since 1958, scientists at the Mauna Loa Observatory in Hawaii have been tracking the amount of carbon dioxide in the atmosphere, measured in parts per million. Last year saw the biggest one-year jump on record, with carbon dioxide levels rising by 3.58 parts per million.

The figure exceeds even the most pessimistic predictions of the U.K. Met Office, which says that record-high emissions from burning fossil fuels cannot fully explain the surge in carbon dioxide.

U.K. scientists note that increasingly severe heat and drought mean that trees and grasses are drawing down less carbon dioxide than in the past, while desiccated soils are also releasing more carbon back into the atmosphere. Conditions were particularly poor last year owing to a very warm El Niño — when warm waters pool in the eastern Pacific Ocean — which fueled hotter, drier weather across much of the tropics.

El Niño ended this past summer, and the Pacific has since shifted to its cooler La Niña phase, which should allow vegetation to draw down more carbon dioxide, say U.K. scientists, who forecast a smaller jump in carbon dioxide levels in the coming year.

This month NASA, NOAA, and European weather officials all determined that last year was the hottest on record, finding that 2024 measured roughly 1.5 degrees C warmer than the preindustrial era. While the world has not yet officially breached the 1.5-degree target laid out in the Paris Agreement, which will be judged according to the average temperature over several years, the new figures mean that goal is almost certainly out of reach.

“Countries have agreed to the 1.5 degrees C global warming limit not out of convenience but out of necessity to limit harm and suffering of people,” said Joeri Rogelj, a climate scientist at Imperial College London. “Even if we are on track to surpass 1.5 degrees C, these reasons don’t change, and only make a stronger case for focused action on reducing greenhouse gas pollution.”