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WMO warns ocean temperatures over the past 12 months have been ‘off the charts’

‘Some records aren’t just chart-topping, they’re chart-busting. And changes are speeding-up,’ said U.N. Secretary-General António Guterres Tuesday

Temperaturas océanos
Coral reefs threatened by rising water temperatures due to climate change and fishing activities on Zanzibar, Tanzania. Åebnem CoÅkun (Anadolu Agency/ Getty Images)
Manuel Planelles

On March 31, 2023, the average ocean surface temperature soared to the highest level on record for that day of the year. And that trend has continued ever since, with record highs being registered every day. Almost 12 months of unbridled sea temperatures have scientists concerned and seeking explanations that include many variables, although all theories are based on a common denominator: the global warming that the planet is suffering due to the action of human beings and the gases that are mainly expelled by fossil fuels.

“It’s scary,” admits Carlo Buontempo, director of the EU’s Copernicus Climate Change Service, referring to the temperatures being observed in the cyclone-forming areas of the Atlantic and the upcoming hurricane season, which begins in late spring, because warm waters provide fuel for such storms. The heat that accumulates in the sea also damages “vital ecosystems and food systems” for human beings, according to the World Meteorological Organization (WMO), which on March 19 presented its report on the state of the climate in 2023. As had already been determined, last year was the warmest year registered for the planet as a whole since reliable records began in the 19th century (although many paleoclimate scientists argue that you have to go back several millennia to find the Earth as warm as it is today).

But that big headline — 2023 the hottest year ever recorded — sometimes overshadows other troubling data. “Sirens are blaring across all major indicators... Some records aren’t just chart-topping, they’re chart-busting. And changes are speeding-up,” said U.N. Secretary-General António Guterres Tuesday. “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,” added WMO Secretary-General Celeste Saulo.

The WMO explains in its report that the heat content of the oceans in 2023 was the highest on record, exceeding the value of 2022. It stresses that this is not an isolated event, but that “all data sets agree that ocean warming rates show a particularly strong increase over the past two decades.” But 2023 — and so far in 2024 — shows a special anomaly.

The average ocean temperature is now half a degree above normal, taking as a reference point the average between the period 1991-2020. Earlier this March, when the absolute daily average temperature record was broken by reaching 21.09 degrees, the anomaly was almost one degree, according to data from the Copernicus Climate Pulse service, which focuses on the analysis of sea surface temperature for the coordinates 60°S-60°N, i.e., excluding polar areas.

What is behind these 12 months of consecutive records? The WMO notes that “different drivers of this change are discussed in the literature, including a change in anthropogenic climate forcing and natural variability.” Buontempo argues that it is possibly a combination of both factors. “Some studies point to an acceleration of the imbalance between the energy reaching the planet and the energy being expelled,” he says. In other words, an acceleration of global warming. “Warmer seas could be a sign of this acceleration,” he adds. “Other hypotheses argue that over a true global warming, these extremes are due to normal fluctuations, such as El Niño or solar radiation. And maybe it could be a combination of both, but it’s clearly not good news.”

The silver lining is that El Niño, a natural pattern that causes surface water temperatures in tropical areas of the Pacific to rise and affects many parts of the globe, is weakening. However, by late summer, La Niña, the opposing phenomenon, could set in, Buontempo says. But in reality, record ocean temperatures are occurring at almost all latitudes, not just in the Pacific. “It’s hard to find a place on the planet where there are no anomalies,” acknowledges the director of the Copernicus Climate Change Service.

It is not only a problem of high average temperatures, but also of extreme events, such as marine heat waves. The WMO explains that such events “have become more frequent, intense and long-lasting since the end of the 20th century,” while marine cold waves “have been decreasing.” “Towards the end of 2023, over 90% of the ocean had experienced heatwave conditions at some point during the year,” the report noted.

Loss of ice and glaciers

Another indicator of the climate crisis is the reduction and loss of glaciers, associated with rising temperatures. According to the WMO: “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.” In addition, it noted, “Antarctic sea ice extent was by far the lowest on record.”

“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,” Saulo stressed in a statement. The WMO report notes that “the number of people who are acutely food insecure worldwide has more than doubled, from 149 million people before the Covid-19 pandemic to 333 million people in 2023 (in 78 monitored countries by the World Food Program). Weather and climate extremes may not be the root cause, but they are aggravating factors.”

The U.N.-linked organization did offer a “glimmer of hope:” renewable energy generation. “In 2023, renewable capacity additions increased by almost 50% from 2022, for a total of 510 gigawatts (GW) — the highest rate observed in the past two decades.”

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