Greenhouse Gases At Unprecedented Levels, Here's What It Means For Global Warming

Greenhouse gas concentrations surged to unprecedented levels in 2023, committing the planet to prolonged temperature rises, according to a World Meteorological Organization (WMO) report released on 28 October 2024.

Carbon dioxide (CO₂), the primary greenhouse gas, is building up in the atmosphere at an accelerating pace, now 11.4 per cent higher than it was two decades ago. 

Between 2022 and 2023, CO₂ levels increased by 2.3 parts per million (ppm), marking the 12th consecutive year with an annual increase exceeding 2 ppm—higher than the rise seen in 2022, though slightly less than increases recorded in the prior three years.

The globally-averaged surface concentration of CO₂ reached 420.0 parts per million (ppm), methane 1 934 parts per billion and nitrous oxide 336.9 parts per billion (ppb) in 2023. These values are 151 per cent, 265 per cent, and 125 per cent of pre-industrial (before 1750) levels.

“Another year. Another record. This should set alarm bells ringing among decision makers. We are clearly off track to meet the Paris Agreement goal of limiting global warming to well below 2°C and aiming for 1.5°C above pre-industrial levels. These are more than just statistics. Every part per million and every fraction of a degree temperature increase has a real impact on our lives and our planet,” said WMO Secretary-General Celeste Saulo.

The report highlighted that greenhouse gas levels tend to spike during El Niño years due to drier conditions and more frequent forest fires in the later part of 2023, which reduce the ability of vegetation to absorb carbon. 

“Natural climate variability plays a big role in the carbon cycle. But in the near future, climate change itself could cause ecosystems to become larger sources of greenhouse gasses” said WMO Deputy Secretary-General Ko Barrett.

The report highlighted that climate feedback issues extend beyond CO₂. Between 2020 and 2022, methane in the Earth's atmosphere experienced its largest three-year increase due to warmer temperatures and unusually wet land conditions, during the 2020-2022 La Niña period.

From 1990 to 2023, radiative forcing—the warming effect on our climate—by long-lived greenhouse gases increased by 51.5 per cent, with CO2 accounting for about 81 per cent of this increase, according to the National Oceanic and Atmospheric Administration Annual Greenhouse Gas Index cited in the WMO Bulletin.

The report also mentioned that the last time the Earth experienced a comparable concentration of CO₂ was 3-5 million years ago, when the temperature was 2-3°C warmer and sea level was 10-20 meters higher than now.

The WMO also said that given the extremely long life of CO₂ in the atmosphere, even if emissions reduce rapidly due to net zero targets, the observed temperature levels will persist for several decades.

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