EVERY year, Shinto priests venture out on to a frozen lake in Japan to view a ridge in the ice which tradition holds is formed by the feet of the gods as they cross the lake. Every year since 1443, they have carefully recorded the date on which the ridge appears. In the first 250 years, they missed just three times — on freak occasions, when the waters did not freeze over. But, recently, the lake has remained unfrozen in seven out of ten years

When does a freak event stop being an anomaly? Worryingly, while we have been preoccupied with Brexit, we have missed recent reports that suggest that a great deal of anomalous climatic behaviour seems to be becoming ominously normative. The Shinto priests are not alone.

Greenland’s ice sheet is approaching a melting threshold faster than expected, scientists at Ohio State University have found. In 2012, it lost four times as much ice as in 2003. In 2018, oceans had their warmest year on record.

Melting ice in the Canadian Arctic has revealed land that has not been seen for at least 40,000 years — and possibly 120,000 years, at the last interglacial, scientists at the University of Colorado say. The region is warming three times faster than the rest of the globe, thanks to a phenomenon: Arctic amplification.

Another Ohio team has discovered that the way in which winds and oceans move heat around the world is changing, too. Without this heat transfer, the world’s hottest spots would be hotter, and the cooler spots would be colder. Ohio, for example, might be 30º colder. That could be changing — and not just for Ohio.

At present, the world’s excess carbon dioxide is absorbed by forest and savanna vegetation. But a study by Columbia Engineering now shows that soil moisture levels, which help to absorb the gases, are falling. Global carbon emissions reached a record high in 2018, rising by 3.4 per cent in the United States alone. The higher concentrations of carbon dioxide in the atmosphere are one of the causes of the changes in the yearly rhythm of freeze-thaw, which is making tens of thousands of lakes lose their winter ice, as the Shinto priests have discovered.

Global warming is not some distant threat. The evidence shows that it is becoming a present reality. That is why the UN secretary-general, António Guterres, warned at the 24th annual UN climate conference in December: “We are in deep trouble with climate change.”

But most worrying is the news from the Barents Sea, which stretches from Norway to the North Pole. It has had an Arctic climate since the end of the last ice age, 12,000 years ago. But its icy-cold surface waters are now mixing with the warmer salty waters of the Atlantic, creating what scientists call a feedback loop which will accelerate the whole menacing process. That could spell the end of cod-and-chips, as the Barents is the home of the world’s largest population of the fish. But it could also be the tipping-point that makes global warming irreversible.

It may, of course, be too early to sound such an apocalyptic tone. But the trouble with tipping-points is that, by the time you realise that you have passed them, it is too late.