Sydney
And Melbourne Copping Record May Heat. The Reason Why Is Scary
21
May, 2016
As
the world warms, the weather is changing in ways far more dramatic
than a little extra heat there, a little less rain there.
Entire
weather patterns are shifting, and we're already seeing the results
in Australia this autumn.
First
up, some dramatic statistics to illustrate the unprecedented
Australian temperature anomalies being experienced in Australia this
month. Then we'll hear from an expert on why it's happening.
- Sydney is a whopping 4.9 degrees above average for May. Sydney's average May daily maximum temperature is usually 19.5. The average is 24.3 degrees so far this month.
- One more time for emphasis, Sydney is almost FIVE DEGREES ABOVE AVERAGE for a whole month. Wow.
- In fact, the Sydney maximum has topped 20 every day in May so far. Tuesday hit 28. The COLDEST day of the month was 1.3 degrees ABOVE the average.
- Hot streaks do not usually last this long. Not even close.
- Melbourne temperatures are also way up this month. It's May 2016 average of 20.3 degrees (to date) is 3.6 degrees above the long term May daily average of 16.7.
- It's a similar picture across Australia. Canberra is nearly four degrees above average so far this May, Hobart and Brisbane three degrees, Adelaide nearly two degrees, and Darwin and Perth both one degree.
- The fact that it's much warmer than usual across Australia is very much in keeping with the long term Australian trend (depicted below), as well as global data showing that the world just had its hottest ever seven months -- and its hottest April by a huge margin.
The
world is warming far quicker in the last year than at any time in
recorded human history. This is a well-documented global phenomenon
with uniform scientific consensus. But even though warming is
accelerating, we're still talking "only" a degree or two
warmer than usual in most places.
But
four to five degrees above normal in Australia's two largest cities
for the first 20 days of a month? Like we said, that's way beyond the
norm. So why is that happening?
Agata
Imielska is a climatologist with the Australian Bureau of
Meteorology. Here's what she told The Huffington Post Australia.
"With
climate change one of the things we have been observing is a shift in
some weather systems. We are seeing high pressure systems sitting
further south and those cold pressure and rain-bearing systems
tracking to the south of the continent."
That
weather map below? It will help explain what Imielska just said.
Don't panic if you can't read a weather map. We'll walk you through
this step by step.
See
the blue lines with (what look like) shark fins lurking in the
Southern Ocean? Those are cold fronts. About the only place they're
impacting right now is Tasmania and New Zealand. High pressure
systems sit over most of Australia. They typically bring warm, clear
weather.
This
map is pretty normal for autumn. Most fronts stay south of the
mainland in autumn. What's not normal is the map looking like this
day after day, after day. A few fronts generally start tracking north
during April and May. This has only happened once so far this year.
Ski
resort PR teams went gaga when
a weak front brought a few centimetres of snow to the Australian Alps
last week even though the snow melted by mid morning.
But
the weather soon turned warm again.
In
2014, a report called "Climate
Change in Australia" was
produced jointly by the Australian Government Department of the
Environment, the CSIRO and the Australian Bureau of Meteorology.
- "a tendency for a contraction of mid-latitude storm tracks toward higher southern latitudes", and;
- "global and hemispheric circulation changes providing causality of cool season rainfall declines in Australia", and;
- "Southern Hemisphere circulation warming expanding the tropics, or Hadley Cell circulation, toward the pole."
In
other words, this describes exactly what we've been talking about.
That the cold fronts -- which bring cooler weather and rain to the
southern states in late autumn, winter and early spring -- are
arriving less frequently.
These
fronts bring not just cooler weather but rain too. Their less
frequent visits to the mainland have meant drastic reductions in rain
to SW Western Australia and parts of the south-east for at least 20
years now. Conversely, parts of the tropics appear to be getting
wetter.
This
image shows that really clearly.
Here's
one more line in the same chapter of the "Understanding Recent
Australian Climate" report that sums all of this up. It says:
"A
contraction of mid-latitude weather systems toward the pole... has
been attributed to anthropogenic greenhouse gas warming and and
springtime Antarctic stratospheric ozone depletion."
In
other words, we're causing these problems. And the warm spell in
Australia this May can be clearly linked to wider patterns. It's no
isolated event.
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