The UN’s World Meteorological Organisation has issued a “red alert” on the climate crisis, citing unprecedented increases in 2023 in greenhouse gases (GHGs), land and water temperatures and melting of glaciers and sea ice.

Global efforts to reverse the trend have been inadequate, said WMO.

WMO’s State of Global Climate Report confirms that 2023 was hottest year on record by a clear margin. Records were broken for ocean heat, sea level rise, Antarctic sea ice loss and glacier retreat.

Heatwaves, floods, droughts, wildfires and rapidly intensifying tropical cyclones caused misery and mayhem, upending everyday life for millions and inflicting many billions of dollars in economic losses, according to the WMO State of the Global Climate 2023 report.

The WMO report confirmed that 2023 was the warmest year on record, with the global average near-surface temperature at 1.45 °Celsius (with a margin of uncertainty of ± 0.12 °C) above the pre-industrial baseline. It was the warmest ten-year period on record.

“Sirens are blaring across all major indicators... Some records aren’t just chart-topping, they’re chart-busting. And changes are speeding up,” said UN Secretary-General António Guterres.

“Never have we been so close – albeit on a temporary basis at the moment – to the 1.5° C lower limit of the Paris Agreement on climate change.” said WMO Secretary-general Celeste Saulo. “The WMO community is sounding the Red Alert to the world.”

“Climate change is about much more than temperatures. What we witnessed in 2023, especially with the unprecedented ocean warmth, glacier retreat and Antarctic sea ice loss, is cause for particular concern,” she said.

On an average day in 2023, nearly one third of the global ocean was gripped by a marine heatwave, harming vital ecosystems and food systems. Towards the end of 2023, over 90% of the ocean had experienced heatwave conditions at some point during the year.

The global set of reference glaciers suffered the largest loss of ice on record – since 1950 – driven by extreme melt in both western North America and Europe, according to preliminary data.

Antarctic sea ice extent was by far the lowest on record, with the maximum extent at the end of winter at 1mn square km below the previous record year – equivalent to the size of France and Germany combined.

“The climate crisis is THE defining challenge that humanity faces and is closely intertwined with the inequality crisis – as witnessed by growing food insecurity and population displacement and biodiversity loss,” said Saulo.

The number of people who are acutely food insecure worldwide has more than doubled, from 149mn people before the COVID-19 pandemic to 333mn people in 2023 in 78 countries monitored by the World Food Programme. Weather and climate extremes may not be the root cause, but they are aggravating factors, according to the report.

Weather hazards continued to trigger displacement in 2023, showing how climate shocks undermine resilience and create new protection risks among the most vulnerable populations.

There is, however, a glimmer of hope.

Action may occur because the cost of climate inaction is higher than cost of climate action, said the report.

Additionally, renewable energy generation has surged to the forefront of climate action for its potential to achieve decarbonisation targets.

"Climate action is currently being hampered by a lack of capacity to deliver and use climate services to inform national mitigation and adaptation plans, especially in developing countries. We need to increase support for National Meteorological and Hydrological Services to be able to provide information services to ensure the next generation of Nationally Determined Contributions are based on science," said Saulo.