June 14, 2018

Is Australia’s current drought caused by climate change? It’s complicated

Rubbish! They are just obfuscating below. It's not complicated at all. Rainfall in Australia regularly oscillates between the North and South of the continent. If there is drought in Victoria, there will be extra rain in Queensland, and vice versa.

And the present pattern is a confirmation of that. While there is reduced rainfall down South we in Brisbane are getting a lot of rain. Autumn and winter here are normally dry but this month there seems to be rain a couple of times a week. And in March it rained nearly every day, with some big falls among that. Hence the headline in March: "Queensland's wet weather breaks dozens of records as rain still falls" and "Far North Queensland residents urged to be vigilant in floodwaters across the region". UPDATE: We also got some quite heavy falls in Brisbane in early July -- Midwinter!


Cairns in March

And the trees and plants are showing the effects of all the rain. This year, my cumquat tree has really leapt for the sky. It's put on at least a foot of growth recently. It seems to know more than the meteorologists do.

We do have some of those splendid fine clear days at the moment that Brisbane winters are known for but we have just as many cloudy days.

How come a humble social scientist like me knows all that while there is no hint of that knowledge from the climate mavens below? They know bupkis but as long as they can drag in some mention of climate change they are in clover


Much of southern Australia is experiencing severe drought after a very dry and warm autumn across the southern half of the continent. Australia is no stranger to drought, but this recent dry spell, and Prime Minister Malcolm Turnbull’s visit to drought-stricken parts of the country, has prompted discussion of the role of climate change in this event.

Turnbull said that farmers need to “build resilience” as rainfall “appears to be getting more variable”. This prompted former Nationals leader John Anderson to warn against “politicising” the drought by invoking climate change. This in turn was followed by speculation from numerous commentators about the links between climate change and drought.

So are droughts getting worse, and can they be attributed to climate change? Drought is a complex beast and can be measured in a variety of ways. Some aspects of drought are linked with climate change; others are not.

In Australia, the Bureau of Meteorology uses rainfall deficiencies to identify regions that are under drought conditions.

Droughts are also exacerbated by low humidity, higher wind speeds, warmer temperatures, and greater amounts of sunshine. All of these factors increase water loss from soils and plants. This means that other metrics are often used to describe drought which go beyond rainfall deficiencies alone. These include the Palmer Drought Severity Index and the Standardised Precipitation Evaporation Index, for example.

This means that there are hundreds of metrics which together can provide a more detailed representation of a drought. But this also means that droughts are less well understood and described than simpler phenomena such as temperature and rainfall.

So is climate change affecting Australian droughts?

As we have so many ways of looking at droughts, this is a more complex question than it might first sound. Climate change may affect these drought metrics and types of drought differently, so it is hard to make general statements about the links between human-induced climate change and drought.

We know that over southern Australia, and in particular the southwest, there has been a rapid decline in winter rainfall, and that this has been linked to climate change. In the southeast there has also been a decline but the trend is harder to distinguish from the year-to-year variability.

For recent short-term droughts in southern Australia, analyses have found an increased likelihood of rainfall deficits related to human-caused climate change. Also, it has been suggested that the character of droughts is changing as a result of the human-induced warming trend.

There is some evidence to suggest that widespread and prolonged droughts, like the Millennium Drought, are worse than other droughts in recent centuries, and may have been exacerbated by climate change. But the role of climate change in extended drought periods is difficult to discern from background climate variability. This is particularly true in Australia, which has a much more variable climate than many other parts of the world.

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