What temperatures do the sixteen colours of the scarf actually represent?

The idea of the warming stripes is simple enough: each band of colour represents a single year, running since 1919 and the hue of colour (blue or red) represents global average surface temperatures for that year. If we take the temperatures of 1961 to 1990 to be our baseline, then blue colours are for years where the average temperature at the Earth's surface was colder than that baseline, and red are for years that were warmer. The stronger the blue, the colder the year; the stronger the red, the hotter.

The attached Climate Scarf Temperature Data PDF details the data Dr Mick Pope used to work out the colour order of our climate scarf pattern:

Column 1 lists the year, column 2 details how the year's temperature deviated from the 1961-1990 baseline temperature and column 3 is the subsequent colour number.

But how much has Earth actually warmed over the last century? What is the difference between the coolest blue and the warmest red?

The short answer is that the surface of the planet has warmed by roughly 1ºC over the last century. This may not feel like much, but this measurable change represents a staggering amount of heat being added to the planet. In fact, Earth is warming at a rate equivalent to adding the energy of about four Hiroshima bombs every second. During our lifetime, the planet has been warming much faster than at any point in human history, and (as far as scientists can reconstruct) faster than any point in the history of life on Earth. For comparison, twenty thousand or so years ago, during the height of what is commonly called the last Ice Age (what scientists call a glacial maximum), there was three times as much ice on the planet and sea levels were something like 120m lower than today. Back then, global temperatures were 'only' about 4ºC colder, yet the planet was radically different. We are already one quarter of the way towards such a transformation of the planet's surface, but in the opposite direction and at a pace about one hundred times faster than when the planet warmed naturally from that frosty period.

All that extra heat is already having disruptive effects on ecosystems and societies around the globe, shifting winds and rainfall patterns, worsening heatwaves, strengthening storms, melting ice and raising sea levels. This warming has reduced the typical volume of Arctic sea ice each summer to about a quarter of what it was just a few decades ago. Tropic coral reefs, like the Great Barrier Reef, now face frequent bleaching from heat stress, something largely unheard of until the last few decades. In 2019, Australia didn't just set new records for heat (and drought), we smashed them. In the six decades prior to 2019, scorching hot days where our continent-wide average maximum was above 39ºC occurred on average less than once every two years. In 2019, we recorded thirty-three days of such blistering widespread heat. Previously, a bad summer bushfire season might see roughly 2% of Australian forests burn. Over the 'Black Summer' of 2019-20, fully 21% of our woodlands were torched, a complex catastrophe that had a lot to do with the record-breaking heat and dryness made far more likely on a warming world. And globally, 2023 marked the hottest year on record, with global temperatures broken by what has been described as a ‘blistering margin’.

The main cause of this warming is well established: burning fossil fuels, which increases carbon dioxide in the atmosphere, thickening the blanket that traps heat close to the planet's surface. Ruminant agriculture and deforestation also make things worse. And Australia is a major contributor to all three of these: we cut down more trees than any other wealthy nation, we have more cattle and sheep than all but a handful of nations, and worst of all we are the world's largest exporter of both coal and liquid natural gas.

Yet it doesn't have to be this way. We have abundant clean energy possibilities, a long track record of agricultural innovation, and are blessed with the oldest continuous culture on Earth and the wisdom they have gained from dozens of millennia learning how to look after Country. It is more than possible for us to collectively choose to love our vulnerable climate neighbours and to honour our Creator by caring for our common home.