The abundance of heat-trapping greenhouse gases in the atmosphere reached a new record last year, “and there is no end in sight to the rising trend”, according to a new report from the World Meteorological Organisation (WMO).
Global averaged concentrations of carbon dioxide, the most damaging greenhouse gases (GHG), in 2022 were “a full 50 per cent above the pre-industrial era for the first time”. They continued to grow in 2023, the WMO confirmed – the increases mean the planet’s overall carbon budget “is shrinking fast”.
The rate of growth was slightly lower than the previous year and the average for the decade, its latest greenhouse gas bulletin concludes. But it adds this was “most likely due to natural, short-term variations in the carbon cycle and new emissions as a result of industrial activities continued to rise”.
Methane concentrations also grew, and levels of nitrous oxide – the third main warming gas – saw the highest year-on-year increase on record from 2021 to 2022.
The bulletin is published to inform the UN Climate Change negotiations at Cop28 later this month.
“Despite decades of warnings from the scientific community, thousands of pages of reports and dozens of climate conferences, we are still heading in the wrong direction,” said WMO secretary general Prof Petteri Taalas.
“The current level of GHG concentrations puts us on the pathway of an increase in temperatures well above the Paris Agreement targets by the end of this century. This will be accompanied by more extreme weather, including intense heat and rainfall, ice melt, sea-level rise and ocean heat and acidification. The socioeconomic and environmental costs will soar. We must reduce the consumption of fossil fuels as a matter of urgency,” Prof Taalas added.
Just under half of CO² emissions remain in the atmosphere while one quarter are absorbed by the ocean and almost 30 per cent by land ecosystems such as forests – though there is considerable year-to-year variability in this. As long as emissions continue to rise, CO² will continue accumulating in the atmosphere leading to global temperature rise. Given its long life, the temperature level already observed will persist for several decades even if emissions are rapidly reduced to net zero, the WMO warns.
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The last time the Earth experienced a comparable concentration of carbon was 3-5 million years ago, when the temperature was 2-3 degrees warmer and sea level was 10-20 metres higher.
“There is no magic wand to remove the excess carbon dioxide from the atmosphere. But we have the tools to strengthen our understanding of the drivers of climate change through WMO’s new Global Greenhouse Gas Watch. This will greatly improve sustained observations and monitoring to support more ambitious climate goals,” Prof Taalas said.
This initiative is to enhance greenhouse gas monitoring to account for both human activities related and natural sources and carbon sinks. It will provide vital information and support for the Paris Agreement goal of limiting global warming to well below 2 degree and aiming for 1.5 degrees above pre-industrial levels.
Although the scientific community has broad understanding of climate change, there are uncertainties about the carbon cycle – and fluxes in the ocean, the land biosphere and the permafrost areas. “These uncertainties, however, must not deter action. Instead, they highlight the need for flexible, adaptive strategies and the importance of risk management in the path to net-zero and the realisation of the Paris Agreement’s goals. Provision of accurate, timely, and actionable data on GHG fluxes becomes more critical,” the bulletin adds.
It calls for greater information on:
- Feedback mechanisms: The Earth’s climate system has multiple feedback loops, for example, increased carbon emissions from soils or decreased carbon uptake by oceans due to changing climate as illustrated by droughts in Europe during 2018 and 2022.
- Tipping points: The climate system may be close to so called “tipping points”, where a certain level of change leads to self-accelerating and potentially irreversible cascade of changes. Examples include the potential rapid dieback of the Amazon rainforest, slowing of the northern ocean circulation in the Atlantic or destabilisation of large ice sheets.
- Natural variability: The big three GHGs have substantial variability driven by natural processes such as El Niño. This can either amplify or dampen observed changes over short periods;
- Non-CO² greenhouse gases: Climate change is driven by multiple greenhouse gases, not just CO². These gases have different atmospheric lifetimes and greater global warming potential than CO².
Carbon dioxide, however, accounts for approximately 64 per cent of the warming effect on the world’s climate, mainly because of fossil fuel combustion and cement production.
Methane remains in the atmosphere for about a decade and accounts for about 16 per cent of the warming effect of long-lived greenhouse gases. Approximately 40 per cent of methane is emitted into the atmosphere by natural sources while 60 per cent comes from ruminants, rice agriculture, fossil fuel exploitation, landfills and biomass burning. “The increase from 2021 to 2022 was slightly lower than the record rate observed from 2020 to 2021 but considerably higher than the average annual growth rate over the past decade,” the WMO notes.
