Canoes, community spirit and sandbags; the very occasional watery tragedy, and heartening tales of rescued old ladies. These have been the currents of British conversation in recent days, or at least of those parts of it not directly dealing with the appalling realities of being submerged. Marvelling from a safe distance at Blackpool sea-foam that looks just like snow, or tittering at troops who turn up without knowing what to do, the general mood has been "oh, to be alive in such times". Meanwhile the "debate" – if it can be so called – was bogged down in the venerable practice of river dredging, before being distracted by a proposal to divert aid for the world's poorest people into building flood barriers at home.

The acres of coverage this past fortnight have contained few clues that an increased incidence of extreme weather events was both predicable and predicted. When the BBC finally got round to discussing how wild weather might link back to a changing climate on Thursday's Today programme, it afforded false equivalence to the caveated observations of leading scientist Professor Sir Brian Hoskins and the clever-clever sideswipes of a retired Conservative politician, Nigel Lawson. It is now time to cast eyes up above low dismal clouds, to confront the sky beyond.

The one point on which Sir Brian agreed with Lord Lawson is that, owing to randomness of a change in the weather, no one incident can ever be nailed absolutely to the evolution of the climate. Any connection can be seen only by tracing a trend line through the scattergun of dots representing individual storms, droughts and floods around the world. At the start of the week, these columns observed how – from forest fires in Norway to the freezing-over of Hell, Michigan – that we appear to have entered a season of record-breaking weirdness insofar as global weather is concerned. Today, at last, we heard a senior politician join the fray, as the Liberal Democrat energy secretary, Ed Davey, made a speech that warned that we might, perhaps, be seeing the shape of things to come. And now, in the pages of this newspaper, Sir Nicholas Stern – the economist whose official review diagnosed "the greatest … market failure ever seen" – gives his verdict that the current floods represent "a clear sign that we are already experiencing the impacts of climate change"; that these are freakish events which can nonetheless be understood as part of a pattern.

The deniers' riposte to the post-millennial cluster of warm and wet British years, or indeed to freakish weather anywhere else, is now reliably distilled down to one seemingly killer fact: the failure of global average surface temperatures to rise in the past 15 years. Some of this stability may be down to the familiar swings of the El Niño cycle; some of it is simply fluctuating ebbs around the deeper tide. What the sceptics choose to ignore is the strength of the foundation stones of the science. It is, after all, more than a century since the heat-hugging properties of carbon dioxide were demonstrated in the lab. No one disputes that hotter air will hold more water, a connection that raises the spectre of more extreme downpours. No one contests that warmer water fills more space, a reality with stark implications for sea levels.

And indeed, it is from the ocean – where the most systematic observations, provided through the Argo network of floating probes, only began around the millennium's dawn – that some of the most alarming data is now coming in. Measured sea levels in places are higher; waves around Europe appear to be bigger; and the water sometimes looks to be getting warmer too. If there has been little rise in average air temperature of late, as the previously under-studied exchange of heat between the Earth and the ocean is factored in, more odd tides are at work in the water than anyone foretold. The bottom line is that as you put more energy into a chaotic system, you get more chaos out. And it may well be that waterlogged Britain is already, albeit unwittingly, discovering that.