It’s a flippant joke that a lot of us make – it’s really cold, can we have a little more of that global warming right now?
But how should we really design our day-to-day weather in the face of climate change, especially when Australia’s east coast experiences a colder-than-normal start to winter?
Here are four ways.
1. Put the weather in a long-term context
Recent cold conditions in parts of Australia have not been seen in decades, but they are not unprecedented.
In Melbourne, for example, the first two weeks of June were the coldest since 1949. In Brisbane, they were the coldest since 1990.
As part of the global warming trend, cold events such as these are becoming less and less likely. But Australia naturally has a variable climate, which means they of course always happen.
And given that instrumental records from Australia only go back 112 years (a relatively short period), it’s actually still possible that we’ll see new records for cold temperatures, even in a warming climate.
Yet Australia’s record hot temperatures are beaten 12 times more often than cold temperatures.
The climate would have to warm up incredibly fast for there to be no cold weather records, and even faster if we were to see no cold weather at all. No one is suggesting that’s the reality.
2. Zoom out for a wider view
Let’s look at a particular day – say, Tuesday, June 13 – using Climate Reanalyse, a visualization platform for climate and weather datasets.
That day was certainly colder than the 1979-2000 average for eastern Australia and Tasmania.
But it was warmer than average in parts of Western Australia and in many places around the world, including large parts of Africa. Meanwhile, parts of the United States and Europe were experiencing significant heat waves.
On that day, the global average was 0.3 degrees Celsius warmer than the 1979-2000 baseline, and that baseline was about 0.6 degrees warmer than the pre-industrial climate.
This is exactly what you would expect from weather variability in a warming climate – variations from day to day and place to place, but an ever warmer climate when you take a view. overall.
3. Look at climate indicators with more “memory”
Watching the day-to-day weather is a lot like watching live stock market updates from a stock exchange. To understand trends and the bigger picture, you need to track them over time and across space.
Since instrumental records only date back to such ancient times, scientists can use climate indicators found in nature. Glaciers, for example, respond to temperature over time, with almost all glaciers in the world retreating in response to a warmer climate.
The oceans have a longer memory than the atmosphere.
Warming oceans are clear, for example, in the East Australian Current, which now extends further south, bringing warmer waters along the southeast coast. This, in turn, pushes fish species further south and devastates kelp forests.
Perhaps the most reliable indicator of global warming is “total ocean heat content” – the total amount of additional energy stored in our oceans, which can store far more than the atmosphere. There has been a steady increase in the heat content of the oceans over the past few decades.
4. Consider the concept of attribution
Determine whether climate change has contributed to making a particular weather event more likely or more severe than it would have been – be it a cold wave, a heat wave or torrential rain – requires a formal attribution study, which looks for a “footprint” of climate change.
A video explaining climate change attribution | CSIRO
Overall, the planet has warmed 1.09 degrees since pre-industrial times. And since 2012, the footprint of human-caused climate change has been clear in a single day of overall Weather report.
Thanks to event attribution studies, we can confidently say that cold extremes are now less likely than they would be in a world without climate change, while heat waves and extreme heat events are much more likely.
For example, climate change has made the recent devastating heat wave in India and Pakistan 30 times more likely.
Our weather intuitions
Our intuitions and common sense are great tools for navigating our daily lives and making decisions. But our first-hand experience is rooted on the scale of centimeters to kilometers, seconds to days.
Our brains are not perfect recorders of data over decades and our memories are subjective.
Vivid childhood memories of hot asphalt on our young feet, cars with hot vinyl seats, and homes without air conditioners affect how we compare the past to today. And we are not exposed to all weathers, especially us city dwellers who spend a lot of time indoors.
Leveraging our intuitions about cold weather to comment on climate change can be compelling.
US Senator James Inhofe snowballed in the Senate in 2015 claiming that if it’s cold, the climate can’t get warmer.
Although widely mocked at the time, these appeals tap into our instinct to look to our experiences to understand the world.
To get out of these local scales, we still need to nurture our intuitions. The data is therefore important.
With data, we can inform and guide our intuitions and overcome our natural focus on the local scale. To be convinced that the climate is warming, we must observe long-term trends and expect fluctuations.
And just as in places like southern Australia where the climate is drying out we always expect wet years, we always expect cold snaps in a warming climate.
It’s instinctive to downplay or doubt the idea that the weather is getting warmer when you’re cold right now. But next time consider these four points.
Michael Grose, Climate Projection Scientist, CSIRO
This article is republished from The Conversation under a Creative Commons license.