Winter’s unseasonal warmth and clear skies are glorious – but a forbidding sign of danger to come | Paul Daley

These unseasonal late-winter days of warmth and clear skies, of the sudden necessity of shorts and T-shirts for the morning dog walk, are at once glorious and somewhat disconcerting.

Spring – the season of renewal, of awakening, of birth and perhaps rebirth – demands to be celebrated. But somehow this year, all of its ridiculously early harbingers feel double-edged for their presaging of the realities of climate change and sea-level rise.

Twenty years ago, perhaps even 10, it was a (reasonably) safe bet to book a ski holiday in the Australian alps for the September school holidays. You could set your calendar around a certain level of climactic and seasonal certainty. Today you wouldn’t hazard a booking for September; June and July are risky enough.

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And by the time you came off-piste in September back then, the lawns at home would need cutting and the outdoor furniture dusting off. I mowed our patch of pointless lawn on Sunday. I can see it growing already.

Once, not too long ago, late September or early October were pretty much the start of barbecue season in eastern Australia. But for the past few weeks the evening winter ambience of Sydney suburbia has been one of late spring – of the sounds of outdoor dining (chatter, laughter, the clink of cutlery) and the aromas of charring protein melded with dreamy jasmine scent.

A softness of contrasting light and a hint of warmth might have crept into the August mornings of yore. But the evenings were still for woolly jumpers, Uggs, doonas and closed bedroom windows. And, if you ventured out, a layer or two under a warm jacket.

Now we are kicking off the doonas, opening the windows and doors.

There is undeniably something discombobulating, disquieting – something contrary to the natural way of things

It was just the other week I was getting about in tracky dacks, a fleece and a beanie to cope with the polar blast that was making Sydney shiver, the doggies’ breath misty in the crisp air. But it was weeks ago, well before the official start of spring, that the noisy miners and the magpies suddenly began going postal (the posties will confirm this), dive-bombing me and the hounds as the birds pre-emptively protected the prematurely hatching chicks in neighbourhood nests.

I think I first saw wattle and cherry blossom in mid-July. It was still cold, then, but nature clearly had been given the signal of the imminent warmth that was part of nature’s emerging pattern of seasonal change.

Meanwhile the magnolia buds – which burst open weeks ago – are already carpeting lawns with their browning petals. Flower beds are bursting with radiant flourishes of varietal colour.

The beauty all around is undeniably glorious. It naturally colours the temperamental – maybe even societal – mood as we emerge from our caves at winter’s end. But there is undeniably something discombobulating, disquieting – something contrary to the natural way of things – about it, too.

Related: Australia’s early spring brings budding flowers, chirping birds – and climate alarm

I can recall, as a younger bloke, occasional early spring days – only to be plunged back into the darkened depths of Melbourne or Canberra winters for another month, maybe two. But this year if you blinked after that cold polar blast of a few weeks back, you opened your eyes in the glorious, luminous full bloom of premature spring .

Given consistent rising global and continental temperatures due to human-induced climate change (Australia’s average is 1.5C higher than 1910) this might be as unsurprising as it is alarming – a beauty masking the very real threat of global peril.

How many times must we be told?

There is no limit, it seems, as the UN secretary general, António Guterres, reiterated this week that the world should “answer the SOS before it is too late’’ on climate change and associated dangerous sea-level rises that pose grave danger to some nations.

It’s more than a little perplexing. For the beauty all around, the springtime tranquillity that makes it feel so good to be alive is also a forbidding siren for a danger already in our midst.

• Paul Daley is a Guardian Australia columnist