local weather report

The weather matters in particular ways to gardeners. If you're a gardener, you need to know what plants are likely to thrive in the particular weather conditions you're expecting. When I started this blog, the weather had been so hot and dry for so long that I was contemplating planting lots of succulents to withstand the challenging conditions. If I had done so, by now they would have rotted away in the moisture resulting from two years of steady rain.

So weather matters. And as it happens, in Australia there is the opportunity to obtain precise and accurate measurements about changes in the nation's temperature and rainfall over a 100 year period.

The Bureau of Meteorology started measuring Australia's weather 100 years ago. There are nearly 800 weather stations across Australia. Over 500 stations are fully automated. 112 stations have information going far enough back and accurate enough to be counted as part of the 100 year record.  The data collected is fed by cables to central stations at the national bureau headquarters in Melbourne. The data is digested, and becomes a record of the history of Australia's weather.

Some figures...

In 60 years, we've lost a third of our total snow cover.

On average, Australia's temperature has gone up 0.9 of a degree.

Sea temperatures around Australia have risen by 1 degree on average, but around Tasmania it has risen an amazing 2.28 degrees, about 4 times the global ocean average. Scientists are not sure why this is so.  

Sea levels have risen everywhere. We've got 9 times the number of flooding events for structures at sea level than we had 100 years ago.

'Every parcel of air, every ocean current, every weather system is now about a degree warmer. And when you go through and do the physics, that's actually a hell of a lot of energy added to the climate system in general.' (Dr Karl Braganza, Australian Bureau of Meteorology)

And that added energy means extreme weather events occurring more frequently and more extremely.

Life cycle and growth patterns of flora and fauna change, as they adapt (or not) to the rising temperatures. For example, butterflies are very temperature-sensitive. Melbourne's common brown butterfly emerges from its chrysalis nearly 2 weeks earlier than in 1940.

Extreme heat days become more common. In 2009 Melbourne's temperature spiked, breaking the Victorian record by 1.6 degrees. The temperature hit 46.5 degrees! The heat led to fires known as 'Black Saturday' in which 173 people died.  And they weren't the only casualties. 370 more people died that week from heat stress.

Wildlife suffer when it is very hot.  In 2010 in southern Western Australia a flock of endangered black cockatoos died when the temperature reached 48 degrees.

photo from WAtoday.com.au

 Because of the rising temperature of the sea, many New South Wales fish have moved south to Tasmania.

 Last year, in southern Western Australia, the sea got so hot, it killed a coral reef, leaving it covered in algae. Whale sharks, normally living in northern waters, were seen in the south, outrunning the hot water, searching for cooler water. This was the biggest heatwave on record to hit Australian waters, and lasted for 5 months.

from Australian Marine Conservation Society website

Changes in ocean temperature affect the type of weather we get. The warmer the water, the higher the rainfall. In the last 2 years there has been more rain in Australia for a 2 year period than ever since records began. The years 2010, 2011 and 2012 saw the worst floods in the history of the state.

from website of Victorian Dept. of Sustainability and Environment

But looked at in the longer term, there has been dehydration across the south of Australia, especially in south-west Australia! The worst drought ever in Victoria started in 2001, and lasted 9 years. When it ended and it started raining, farmers rejoiced at first, until their crops were inundated by floodwaters.

This is a pretty confronting post, but I want to face reality, not deny it. The point is that global warming is not something that our children will have to worry about it in the future - it's here with us now. After 2 years of mild summers, the weather forecast for this summer in Victoria is hot and dry, with the risk of fires as great as it was for Black Saturday in 2009.

So it's more than simply choosing plants that we gardeners have to think about.  How are we going to prepare for the changes? In Alice Through the Looking Glass, the Red Queen said that it takes all the running you can do to stay in the same place. But that no longer works. Because the same place has disappeared into the past, and no matter how fast you run, you'll never get back there again.

A biblical warning against global warming, by Jean Gouders

Source: Catalyst, ABC TV, 15/11/2012