The wind grows stronger

Trends in wind speeds
Trends in global wind speeds … graph adapted from study by Zhenzong Zend et al 2019

We are told constantly the planet is getting warmer, but wind speed trends are rarely mentioned.

The graph above shows wind speed trends over land.

There was a downward trend until 2010, then it started getting windier.

Wind speeds over the sea have been going up for decades, with a study showing the fastest increase in the Southern Ocean.

Young and Ribal [2019] assessed trends in oceanic wind speed and wave height from 1985 to 2018 using satellite altimeters, radiometers and scatterometers.

“The largest increases occur in the Southern Ocean. Confidence in the results is strengthened because the trends were confirmed by all three satellite systems,” they said.

It is a mystery why land wind speeds went down, while sea wind speeds increased.

But make no mistake, land and sea wind speeds are now both going up and will shape Tasmania’s future.

The state is already a windy place, being located in the Roaring 40s wind belt.

Gaining access to local historic wind speed data is unfortunately not as easy as obtaining rain and temperature records.

We know it is getting warmer.

Rainfall trends are harder to assess, because annual rainfall totals only tell part of the story.

The Bureau of Meteorology acknowledges that the timing of annual rainfall has changed in Tasmania.

This is where I fall back on local anecdotes.

What I have seen in 10 years on a Huon rural property is a drying trend.

There is less drizzle, but more short, heavy deluges.

There seems to be more wind, and warmer summer temperatures.

Normally I would put this down to decadal variation, but what I see matches current observations elsewhere.

What’s it all mean?

Where wind, warmth and rain intersect is in evaporation.

More wind and warmth creates dry soil and dry forests, even if rainfall remains static.

Dry forests burn, especially when it is windy.

We are seeing a recipe brewing for repeated epic bushfire seasons in Tasmania.

It is hard to imagine a bushfire as I look outside today at the lush green hills and thick fog over the river.

But the reliable spring and summer gales, the cracked soil around the dams, and the hundreds of dead trees on the hills are a huge hint.

Hopefully our community managers are taking notice of the brewing recipe.

It’s not hand-wringing time, but it is time to be prepared.

For rural dwellers, fire pumps and fuel removal strategies are essential, and you should have ember-intrusion prevention measures.

If you want to know more about wind trends, look up Australia’s wind and hydrology expert at CSIRO, Tim McVicar.

Meanwhile, here’s a recent story about the latest Australian weather trends.

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Tasmanian Life