We might be forgiven for thinking that climate change is a gradual and steady process, as all the Government and international plans seem to point that way. The recent Climate Change Bill aiming to reduce carbon emissions by 80 per cent of the 1990 level by 2050 implies that reducing it bit by bit is the way forward.

However, there can be abrupt changes and the evidence is seen in a lovely small arctic-alpine flower – the Mountain Avens or Dryas Octopetala. It’s the national flower of Iceland, and can be found in cold mountainous areas – indeed the only patch in Yorkshire is on a hillside behind the village of Arncliffe in Littondale.

Remnants of this woody, ground hugging plant with a small white and yellow daisy-like flowers were found preserved in lake deposits and silt at a time when it should not have been growing, and the only explanation is that the temperature was much lower than expected.

About 15,000 years ago, the last Ice Age ended with the ice melting all over Europe. Locally, the glaciers terminated in Bingley, leaving the moraine ridge the town is built on and the higher ground of Hirst Wood, and this was all the result of changes in the planet’s orbit leading to more heat from the sun.

The temperatures rose for the next 2,000 years until 12,800 years ago, when the glacial conditions suddenly returned for around another thousand years. It must have been a shock to our early ancestors, and it occurred because the circulation of the Atlantic Ocean slowed down with all the fresh water from the melting ice.

And then, 11,600 years ago, it all started to heat up again, and very quickly indeed, up ten degC in less than 40 years and these sudden changes were mirrored in the associated rises in sea level.

Since the ice melted, sea level has risen by 120 metres – about one metre each century – but around 14,000 years ago, just before the Dryas period, it rose by 20 metres in 500 years, at a rate of 40mm a year, much faster than the current rate of 3mm.

Such sudden climate change took place in the recent past due to variations in the Earth’s orbit, but now we have added increasing amounts of CO2 to the system and so risk further sudden changes in periods of just a few years.

We won’t be able to say that we were taken by surprise.