Climate change is already affecting the landscape of Tasmania through more intense fire seasons. This threatens species like the Pencil Pine. In the last few decades, there has been an increase in fires caused by dry lightning strikes, and this has been impacting on vegetation types that are not fire adapted.
A recent review of how much climate change has already impacted on Tasmania highlights how broad these effects are on the landscape.
Erin Cooper, writing for the ABC, identified the following impacts that are being felt in mountain areas.
- the state is about 1oC warmer than a century ago
- hot weather is more extreme than it was
- it is now drier in Tasmania, with the decline strongest in late Autumn, heading into early winter
- it appears that the state is getting less snow, although there is no long term data to back this up.
“The ABC investigated how much the island state’s climate has changed in the past 100 years.
Climatologist with the Bureau of Meteorology in Tasmania, Ian Barnes-Keoghan, said the bureau had been collecting temperature observations since the late 1800s — and the data paints a very clear picture.
“It doesn’t matter how you cut it up, you still get the same message that temperatures over Tasmania have risen over the last century, particularly since the 1950s,” he said.
“It’s such a clear-cut story.”
Averaged over the entire state, Mr Barnes-Keoghan said Tasmania is now about a degree warmer than it was a century ago.
But hot temperatures are also now more extreme than they used to be, with fewer very cold days.
“We’re not saying that the temperature everyday is now a degree warmer than it was, but the average has moved up and we’re seeing more of those extremely high temperatures, so your 35 and 40-degree days,” Mr Barnes-Keoghan said.
“Since 1910, there’s been 12 days where somewhere in Tasmania has reported a temperature of 40 degrees or more. Four of those occurred in the first 93 years, the other eight only occurred in the last 17, and two of those were this year.”
“It’s often those extremes that people really notice.”
As for the argument that the warming of the climate is cyclical, Mr Barnes-Keoghan said there was no reason why people should expect average temperatures will cool down again.
In fact, Scientists writing in the journal Nature this week said there was no evidence for “globally coherent warm and cold periods” over the past 2,000 years prior to industrialisation.
“We have a very good understanding of the mechanisms behind this warming, so the significant cause has been an increase in the concentration of greenhouse gasses in the atmosphere,” Mr Barnes-Keoghan said.
“So just by simple physics that leads to an increase in the average temperature because more warmth is trapped close to the surface.”
When it rains, it pours
Perhaps unsurprisingly, it is now also drier in Tasmania, with average rainfall across the state decreasing.
“There is less rain, on average, now than there was 40, 50 years ago, but there’s a couple of things mixed in there,” Mr Barnes-Keoghan said.
“One is that we still get wet years, like it rained a lot in 2016 — but the wet years have become less common and the dry years have become more common,” he said.
He said the decline is strongest in late Autumn, heading into early winter.
Mr Barnes-Keoghan explained rainfall now behaves differently than it did in the past.
“[In the past,] you’d get a couple of dry years, then a couple of wet years to make up for it,” he said.
“But sometime around the mid-70s, that pattern seems to have changed.
“Instead of having a mixture, it went to getting several dry years in a row, then a wettish year but not really that exciting, then a couple of dry years and just not getting those recharge years.”
But explaining why is a bit more complex.
“Rainfall is complicated, but one of the reasons there’s been less rainfall is there are less rain-bearing systems,” Mr Barnes-Keoghan said.
“That partly comes about because of an increase in high-pressure systems — that’s a known and expected consequence of increasing greenhouse gases.
“Rainfall is hugely variable from year to year, much more variable than temperature, so picking out trends in rainfall is much harder.”
Mr Barnes-Keoghan also said the warmer atmosphere holds more moisture, so when it does rain, it’s now often in quicker and heavier bursts.
But what about wind and snow?
So if Tasmania’s drier, is it also getting less snow?
Mr Barnes-Keoghan said while it certainly seemed that way, there was no available data to back that up.
“The bureau does not have a good long-term collection of snow data,” he said.
That’s because it doesn’t snow that often over most of Tasmania and in particular, it doesn’t snow that often in populated areas.
Mr Barnes-Keoghan said a lot of the historical observations really relied on somebody being there to take the measurement, which didn’t always happen.
“I’ve been here for a long time and I get the impression that snow is less common than it was, but that’s completely an anecdote,” he said.
Wind is also hard to measure, though Mr Barnes-Keoghan said average windspeeds were decreasing, albeit not by much.
He said the bureau had only really collected data on wind since the 1990s, and even then, it might be skewed because equipment had been positioned in locations known to be particularly windy.
“To measure rainfall you basically need a jam jar, I mean we have very sophisticated jam jars which are calibrated, but measuring wind speed is really difficult,” he said.
“The instruments we’ve got now were really only developed during the 1950s and only became widespread in Australia during the 80s and 90s. [They] only became really important around the 90s so we’ve really only got measurements since then.”
As always, ‘action is the antidote to despair‘.
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