It’s a casual joke many of us make – it’s freezing cold; can we get more of that global warming now?
But how should we envision our day-to-day weather in the context of climate change, especially when Australia’s east coast is experiencing a colder-than-usual start to winter?
Here are four ways.
1. Put the weather in a long-term context
Recent cold conditions in some parts of Australia have not been seen for 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 hardest since 1990.
Under the global warming trend, cold events like this are becoming less and less likely. But Australia has a naturally variable climate, so they still occur naturally.
And since Australia’s instrumental records go back just 112 years (a relatively short it’s actually possible we’ll see new record-breaking temperatures even in a warming climate.
Yet record high temperatures in Australia are broken 12 times more often than cold.
The climate would have to warm up incredibly fast to break zero cold records, and even faster if we didn’t see any cold weather. No one is suggesting that this is the reality.
2. Zoom out for a wider view
Let’s look at a particular day – Tuesday, June 13 – using Climate Reanalyser, a platform for visualizing climate and weather data.
That day was colder than the 1979-2000 average in Eastern Australia and Tasmania.
But it was warmer than average in parts of Western Australia and many places worldwide, including much of Africa. Meanwhile, parts of the United States and Europe dealt with major heat waves.
On this day, the global average was 0.3 degrees Celsius warmer than the 1979-2000 baseline, and this baseline was about 0.6 degrees warmer than the pre-industrial climate.
This is exactly what you expect from weather variability in a warming climate – variations from day to day and place, but a consistently warmer climate when you look at the wide view.
Australia has had more cold, wet, and stormy weather than usual this year. Photo: Getty
3. Look at the climate indicators with more ‘memory.’
If you look at the weather daily, it’s like watching the stock market’s live updates from one exchange. To understand the trends and the bigger picture, you must follow them in time and space.
Since instrumental data only goes back so far, scientists can use climate indicators found in nature. For example, glaciers respond to temperature over time, with nearly all glaciers worldwide retreating in response to a warmer climate.
The oceans have a longer memory than the atmosphere.
For example, ocean warming is evident in the East Australian Current, extending further south, bringing warmer waters along the southeast coast. This, in turn, drives fish species further south and devastates kelp forests.
Perhaps the most reliable indicator of global warming is the total “heat content of the ocean” – the total amount of extra energy stored in our oceans, which can keep much more than the atmosphere. In recent decades, the heat content of the sea has steadily increased.
4. Consider the concept of attribution
Determining whether climate change has made a given weather event more likely or severe than it would have been — be it a cold spell, heat wave, or flooding rain — requires a formal attribution study, which looks for a “fingerprint” of climate change.
A video explaining the attribution of climate change | CSIRO
Overall, the planet has warmed 1.09 degrees since pre-industrial times. And since 2012, the man-made fingerprint of climate change has been evident in every day of global weather.
Thanks to research into event attribution, we can confidently state that extreme cold is less likely now than in a world without climate change, while heat waves and extreme heat are much more likely.
For example, climate change made the recent devastating heat wave in India and Pakistan 30 times more likely.
Our weather intuition
Our intuition and common sense are great tools for navigating our daily lives and making decisions. But our first-hand experience is rooted in the scale from centimeters to kilometers, seconds to days.
Our brains have not been perfect data loggers for decades, and our memories are subjective.
Childhood memories of hot asphalt on our young feet, cars with hot vinyl seats, and homes without air conditioning influence how we compare the past with the present. And we are not exposed to all weather conditions, especially city dwellers who spend much time indoors.
Using our intuition about cold weather to comment on climate change can be compelling.
US Senator James Inhofe famously snowballed the Senate in 2015 to argue that the climate can’t warm up when it’s cold.
Although this was widely derided at the time, these calls pull on our instincts to use our experiences to make sense of the world.
We need to give our intuitions a little more input to get out of this local scale. So data is important.
With data, we can inform and guide our intuitions and overcome our natural focus on the local scale. To ensure the climate is warming, we must watch long-term trends and expect fluctuations.
Tweet from @davejorgenson
And as in places like South Australia, where the climate is drying up, we expect some more wet years; we still expect cold spells in a warming environment.
It’s instinctive to downplay or doubt the idea that the climate will get warmer if you’re cold 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.