I was asked by the Adelaide Advertiser newspaper to write a short piece last week which addressed the question “Does all the recent rain across the country prove man made climate change is real?“, in less than 500 words. My response, given below, appeared in the print edition on Thursday 9 September 2010:

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Does all the recent rain across the country prove man made climate change is real? No.

As Dorothea Mackellar wrote over a century ago, Australia is naturally “A land… Of droughts and flooding rains”.

Putting the impossible issue of ‘proof’ aside, scientists certainly do expect climate change to lead to an increase the frequency and intensity of extreme weather events. After all, a warmer planet holds extra energy, making today’s climate system more dynamic than when Mackellar penned her poem.

In short, as the Earth’s atmosphere traps more heat due to an increase in greenhouse gases, it triggers more evaporation of water from the oceans. Average global humidity and precipitation rise in response.

As such, climate scientists predict increasingly energetic storms, heavier bursts of rain, and more intense flooding. In many parts of the world, deeper droughts and longer, hotter heat waves are also forecast.

So, while it is impossible to attribute any one event solely to human-caused warming, a useful analogy is that “weather throws the punches, but climate trains the boxer”. Another way to look at it is that human impacts are “loading the climate dice” towards more unfavourable (and previously unlikely) outcomes.

 We have probably witnessed this in the unprecedented heat wave in Russia and record floods in Pakistan. These impacts cause great human misery and severe economic and environmental damage.

Earlier this year in Australia, the Bureau of Meteorology released a Special Climate Statement on the recent exceptional rain and flooding events in central Australia and Queensland. February 28th 2010 was the wettest day on record for the Northern Territory, and March 2nd set a new record for Queensland. Over the 10-day period ending March 3rd, an estimated 403 cubic kilometres (403,000 gigalitres) of rainfall fell across the NT and QLD. Extreme, indeed.

It’s clear that if such ‘unusual’ climatic events are visited upon us ever more regularly, then there will be practical limits to adaptation, or at least exponentially rising costs involved in coping.

The need for action on eliminating our dependence on fossil fuels is urgent and our window of opportunity for avoiding severe impacts of climate change is rapidly closing. Yet the obstacles to change are not principally technical or economic, they are political and social. But that’s another story