Blame it on the Weather… Or Climate Change?

We’re very pleased to introduce Karina, a self-confessed science nerd and another new Rubies contributor for 2013! Karina is currently studying Honours in Geosciences at the University of New South Wales, and is passionate about getting everyone else as enthusiastic about science as she is! In her first post, she dives head first into the details of recent weather extremes and how they relate to climate change.

floodwater(1)The sunburned country that Dorothy Mackellar described, “of droughts and flooding rains,” really has shown off all her tricks in the last month, with equal measures of flood and fire, taking lives and causing millions of dollars of damage from Queensland to Tasmania.

With record heat waves causing the Bureau of Meteorology to extend its temperature scale on its forecast charts, catastrophic fire conditions, and Cyclone Oswald bringing insane rainfall to Queensland and New South Wales, it’s tempting to cry out to the heavens, “Go home, weather! You’re drunk!”

But Australia isn’t the only continent experiencing weird, extreme weather at the moment – so is this climate change?

To answer this, we need to first understand the basic mechanics of weather.

Much of it is essentially controlled by the ability of air to move around the globe, heating up and cooling down, gaining or losing moisture in the process; and the rate at which it is able to do this.
Now that’s summed up, let’s explore January’s weather in two parts – the hot and dry, then the cold and wet – and then see how this fits in amongst other record breaking weather events around the world and how this fits into the climate change story.

The Hot and Dry

AWAP Highest Max. Temp

Image: Bureau of Meteorology

The end of 2012 was already hotter and drier than normal in many parts of Australia. Hot and dry air from central Australia that normally would have travelled off towards the ocean and cooled down became trapped over the continent by pressure systems offshore towards Australia’s south and west. As this air remained over the land, it continued to heat up and grow, heading east in the process. It was about this point that a lot of heat records were broken – not just in terms of individual maximum temperatures in local areas, but the national average and the length of the heatwave itself.

Some respite was felt as this hot mass of air eventually moved off the east coast of Australia, allowing many places to cool down. However, a separate heat wave hit Western Australia just as the east was cooling down in mid-January. Then similar to earlier in the month, air heated up in central Australia and spread quickly, again pummelling New South Wales with extreme heat (>45°C in Sydney, anyone?).

As all this air finally cleared out to sea and cooled down, the Bureau of Meteorology declared the heatwave over on Jan 19th. Not that that meant a break for us weather-weary Australians…

The Cool and Wet

Enter Cyclone Oswald, stage right. (And by right, I mean east.)

Oswald hit northern Queensland, and though big, didn’t start making news until it started to break down and move south. Like the cute new Doctor Who companion that I’m totally girl crushing on, ex-Tropical Cyclone Oswald teamed up with a low pressure friend to hit the east coast.

But this duo isn’t so friendly – it’s brought heavy rains to most of the populated eastern coast of Australia, leading to flooding in south-east Queensland and north-east New South Wales. Unfortunately, this includes many areas that were just getting back together after flooding in 2011. After breaking heat records barely weeks earlier, many places are now breaking rainfall records, with some centres receiving close to their annual average rainfall in just a few days.

Information is still coming to light about what happened to Oswald, but the good news is that it appears most of the rainfall has stopped, and water is just moving through catchments now. But is this something we need to be prepared for? Are 1-in-100 year events now common? Is this a result of *gasp!* anthropogenic climate change?

Weather or Climate?

FACT: Climate is not the same as weather.

Weather is the day-to-day changes in conditions. As a hypothetical, Sydney could be was 42ºC and sunny one day, then be 25ºC, overcast and windy the next. That’s weather.

Climate, however, could be described as weather trends over the long term – this is at least on the decade-to-decade scale, but can look at whole centuries, even millennia. In earth sciences, this is just the blink of an eye – we deal with scales of at least tens of thousands of years. For example, we could look at how the 1950’s were different to the 2000’s (50’s were cooler and wetter), or how the Jurassic was different to today (the Jurassic was warmer and wetter than it is today).

Now, let’s put that into the context of climate change. The Intergovernmental Panel on Climate Change (IPCC) definition uses some pretty fancy jargon, but essentially says that climate change is when the climate (long term trends in temperature, rainfall etc) goes beyond natural variation (think of the differences between summer and winter) and is sustained over the long term (at least a few decades).

Science shows that climate change means that the starting conditions (mainly temperature and moisture) for a weather event are different to how they were in the recent past. So if the air over the Pacific is warmer and wetter due to evaporation rates rising proportionately to temperature rises because of increased concentrations of greenhouse gases in the atmosphere then cyclones are more likely to form. More cyclones forming in the west Pacific means more cyclones hitting north-east Australia.

Basically, climate change means that the initial conditions in which weather events form is different. Think about weather in terms of the chance of particular events happening – changing the global climate essentially “loads the dice”, increasing the probability of more extreme events occurring.

Whether an individual weather event is caused by climate change is impossible to say, but it is certain that the intensity and frequency of weather events that would be considered extreme now (droughts, floods, heat waves, even cold snaps) are likely to become more commonplace in the near future. There is also the possibility that the new extremes would be beyond what we’ve seen before.

To stall this would require rapid change in attitude and implementation of innovative technology at the global scale. But the effects of our actions are non-linear – a recent article in Nature produced a model showing that the likelihood of any actions’ success decreases rapidly, the longer we wait. Given the enthusiasm towards change that has been seen internationally, looks like we should be bracing ourselves and looking to science to manage, rather than prevent, extreme weather effects in the future.

Want to read more?

You think being a scientist is all about being in the lab and the field, but really you’re a professional reader with some fun stuff thrown in. (But I still love it!) I thoroughly encourage further research to draw your own conclusions – after all, that’s science!

Australian heatwave:

Cyclone Oswald:

Extreme weather and climate change:


1 Comment

Filed under Stand Back: Science!

One response to “Blame it on the Weather… Or Climate Change?

  1. Scott

    That was very well written 🙂

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