How we experience climate change

One of the challenges of communicating around the topic of Climate Change is that it is simultaneously:

  • A profound threat to humanity.
  • Not currently obvious to residents of many parts of the world.

Worlds which are 2 °C or even 3 °C warmer will be changed in ways which are – in places – utterly disastrous for humankind, and which – in my opinion – threaten our advanced civilisation.

I am ‘all in’ for doing what we can do to minimise the harm to which we have already committed ourseves and our children.

But although evidence for climate change is ubiquitous to people who look for it, for people living in the UK, it can also be easy to overlook. Nobody has direct awareness of changes of annual average temperature of 0.02 °C a year.

Nonetheless, older people – a group of which I count myself a junior member – are aware that things have changed over their lifetime.

We have a sense that the frequency and intensity of extreme weather – events which catch our attention – has changed. For example many people think:

  • “There isn’t as much cold weather as there used to be.” Or
  • “There are more nights when it doesn’t cool down than there used to be”. Or
  • “There are more hot days than there used to be”.

A new page from the Met Officethe Global Climate Extremes Dashboard – highlights the nature of these changes.

How we experience climate change

The Met Office page shows an analysis of global historical data, rather just UK data. But the categories of analysis match my own qualitative sense of what is changing in the UK.

The authors chart the following:

  • The increasing number of warm days per year.
  • The decreasing number of cold nights per year.
  • The increasing length of periods of warm weather.
  • The increasing temperature of the hottest days.
  • The increasing rainfall on the wettest days.
  • The increasing tendency for rain to fall in intense events.

As an example, the figure below shows the increasing number of warm days each year. A warm day is defined as being in the top 10% of temperatures from the period 1961 to 1990.

Click for a larger version. The plot shows the change in the number of warm days per year – days when the maximum temperature exceeds the 90th percentile of the distribution for the period 1961-1990 – expressed as a difference from the 1961-1990 average. Over my lifetime (so far) the number of hot days in each year has increased by more than 20 days per year. Figure copied from the Met Office Site.

The Met Office Page and the paper on which it is based are significant and valuable for three reasons.

Firstly it highlights how we as individuals experience climate change. Without specifically counting hot days or measuring temperatures, over periods of a few decades people notice that ‘things are different’ without being aware of changes in the underlying average.

Secondly, it highlights the insidious nature of climate change. These analyses show that we are heading towards dramatic changes, but at a rate which it is hard for people to perceive directly over just a year or two.

Finally, from a metrological perspective, these analyses are robust against almost all systematic biases in the underlying data set. These analyses typically don’t even rely on instruments being calibrated!

The joint trends of increasing frequency and magnitude of warm extremes and decreasing frequency and magnitude of cool extremes, is a particularly striking signal of trouble in the decades to come.


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