Perth smashed its Previous heatwave records last week, after sweltering through six days in a row over 40℃ – and 11 days over 40℃ this summer so far. Perth has also experienced widespread power outages. A bushfire in the city’s north.
While the heatwave was unprecedented and extreme, for climate scientists like myself, it’s not surprising. Southwest Australia ConsideredThe long-term warming/drying trend is very pronounced in this area, making it a hotspot of climate change.
Over the last century, the average global temperature has risen by more than 1℃. This has seen the number of days over 40℃ more than Double in Perth.
To definitively state whether last week’s heatwave is a direct result of climate change, we’d need to carry out a formal attribution study. We do know that these types of extreme events are likely to increase based on climate models. More frequent.
What’s driving this heatwave?
Easterly winds that blow over hot, dry deserts bring very hot, dry weather to Perth.
These winds are brought about by “anti-cyclones” (or high pressure systems), which are a prominent feature of Perth weather, and we see these almost every day in our weather charts. Their impact depends on where they’re located and how they move.
The Great Australian Bight was sheltered by an anti-cyclone, which caused the heatwave. But that’s not the whole story, as the so-called “west coast trough” – another key feature of Perth summers – also plays a key role in determining how hot it gets.
Troughs can be described as elongated areas of low atmospheric pressure. If located offshore, the west coast Trough will essentially block or weaken the afternoon ocean breeze.
When it’s stationary at the coast, it tends to bring warm north-easterly winds, which was the case during the heatwave. As the trough moves inland, we get cooler conditions, as we’ve been feeling this week.
These anti-cyclones, according to climate change models are becoming more intense and frequent. Indeed, A 2018 study confirmed the frequency of anti-cyclones is increasing between 30-40⁰ south of the equator, which includes southern Australia.
The east is also known for its hot and dry winds. Expected to get more intenseWA will be able to take on even more heat.
The outlook starting from here
Australia has already warmed by about 1.4℃ since 1910. If global emissions continue to rise, then Australia will experience the hottest day in the year of high-emissions. 4 to 6℃ warmer by 2080–2099, compared to 1995–2014.
While climate models typically have large uncertainties when it comes to predicting rainfall, southwest WA is one of few regions worldwide where the vast majority of climate models agree we’ll see a marked decline in winter and spring rainfall – by In a scenario with high emissions, up to 30%.
All this implies we’re further increasing the chances of more consecutive days above 40℃, as we in Perth have just experienced.
Extreme heatwaves or dry spells can have a severe impact on wildlife. For example, the region was subject to an extremely dry winter in 2010, followed closely by a hot and humid summer in 2011 and then a heatwave at sea in March 2011.
They Combination impactThis led to coral bleaching and mass tree deaths. The mass death of plants on land, seagrass, kelp, and an endangered terrestrial bird species caused a population collapse and plummeting breeding success of marine penguins. There was also an outbreak of terrestrial woodboring insects.
What does this drying-heating trend mean for bushfires ResearchPublished late last year, the study shows that climate change has significantly increased the frequency and severity of megafires in Australia. A forest megafire is a bushfire which burns more than 1 million hectares (or 10,000 kilometres).
The study showed that Australia has had four megafires in the last 90 years. Three of these megafire years occurred. After 2000.
Bushfires are a common occurrence in WA. Further warming and drying will not only increase bushfire risk but also lead to longer fire seasons.
What can we do?
The science is unambiguous. We must reach net zero emissions as soon as possibleTo avoid catastrophic climate change, extreme heat events like those we experienced in Perth will just become more common.
But there is hope, as our models show we can avoid the worst of these impacts under a low emissions scenario, which could see global warming limited to 1.5℃ this century. This requires bold, urgent action.
Australia must implement urgently a plan to deal with future heatwaves. National policyon urban greening and housing that takes into account more intense heat extremes to better manage heat.
There is still a month left of summer, so it is important that you find ways to keep cool. Simple steps can go a long way, too, such as keeping blinds closed and shutting doors in rooms you’re not using.