carbon emissions rise to new record

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New research shows that atmospheric carbon dioxide concentration last year saw the largest one-year increase since records began in 1957.

Levels in 2024 hit 423.9 parts per million (ppm), or an increase of 3.5 ppm from 2023, and 152% of the pre-industrial level, according to the World Meteorological Organization (WMO). This compares with an annual average rise of 0.8 ppm to 2.4 ppm a year in the decade from 2011 to 2020.

The acceleration has concerned scientists given annual fossil fuel emissions remained largely constant, suggesting reduced carbon absorption by land and ocean “sinks” and rising wildfire emissions may be driving a feedback loop.

This came alongside a separate study led by Exeter University indicating a breach of the first so-called climate tipping point, as warm-water coral reefs experienced ‘unprecedented mortality’ following repeated mass bleaching events during successive ocean heatwaves.

Also this week, in the lead up to the UN COP30 climate summit in Brazil, the World Weather Attribution (WWA) group of scientists released a study on how extreme heat had changed in the decade since the Paris accord.

In 2015 when the Paris summit took place, the world was 1C warmer compared with the pre-industrial period. It has warmed an additional 0.3C since then, it is estimated. Even if countries follow through on their Paris pledges, which they have so far failed to do, the global average temperature is projected to rise by 2.6C by 2100.

How we made it

The WMO publishes annual Greenhouse Gas Bulletins, reporting on atmospheric concentration levels and growth rates of the main long-lived gases: carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O).

These time series are available from the World Data Centre for Greenhouse Gases, as monthly or annual data.

The second most important greenhouse gas, methane is responsible for about 16% of warming with a molecule that holds more heat than CO₂ but has a shorter lifespan. Its levels in the atmosphere also reached a record last year, at 1942 parts per billion (ppb).

Almost two-thirds of methane is emitted as a result human activities, with the rest coming from natural sources. Unlike carbon dioxide, its growth rate slowed last year compared with the average rate over the past decade.

Finally, nitrous oxide averaged 338 ppb in 2024, also growing at a slower rate than the last decade’s average. Its excess is generally produced from agriculture and soil management, as a result of fertiliser use.

We visualised atmospheric concentration and growth rate for carbon dioxide, as the “single most important” greenhouse gas to highlight the latest growth record. It is responsible for about 66% of the warming effect by greenhouse gases, according to the WMO.

The authors of the WWA study on extreme heat since the Paris accord kindly shared their data, which included the number of hot days per country (and in some cases states/provinces) at several levels of warming.

These were at: +1C warming a decade ago compared with pre-industrial levels; +1.3C current estimated level of warming; +2.6C projected warming by 2100 if countries fully implement their Paris goals; and the +4C projected warming previously expected before the Paris Agreement.

“Hot days” were defined as those that are warmer than 90% of days over the 1991-2020 period in a given area.

We created a simple nation-by-nation drop-down chart that allows readers to lookup their country or those of interest, to understand how the frequency of such hot events had changed since the Paris accord. It also shows how much more they are projected to increase under current policies (a lot!) and under the scenario expected when it was drawn up.

In a 2.6C warmer world, the planet will experience 57 more hot days on average than it does today. In a 4C warmer world, this number doubles to 114 additional hot days.

And of course such global averages hide regional trends. For nearly 30 countries the difference between these two scenarios translates to a difference of 100 additional hot days annually.

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