Will Steffen: a chilling message about a warming climate

Will Steffen spoke at Il Passagio in September 2015
Will Steffen spoke at Il Passagio in September 2015

Upon hearing that the planet had warmed by one degree Celsius, a conservative politician said that he could get on a plane in Melbourne and get off in Sydney an hour later and find the temperature higher by a comfortable six degrees, so what’s the problem?

In fact, a global rise of one degree has increased the incidence of extremely hot days in southeast Australia by a factor of ten. It’s because temperatures, like most natural phenomena, arrange themselves along Bell curves. And a shift to the right of just one degree has massive ramifications, not at the height of the curve but at that very low, very sensitive-to-change high end. If it seems that bushfires are starting earlier in the season and becoming more frequent lately, that explains why.

Explaining this at the Bermagui Institute Dinner at Il Passagio on 23 September was climate change expert Professor Will Steffen, a member of the Australian Climate Commission until it was disbanded by the incoming Abbott government in September 2013.

Steffen started with the basic science. Until about 1960, the planet enjoyed a period of climatic stability, the 11,500 year Holocene Epoch. It was, he said, a kind of “sweet spot” in Earth’s history. But from 1960 we have seen a rapid departure, with each decade warmer than the last. That’s where we come to our present one degree raise. But this makes the problem seem a lot smaller than it is (quite apart from our Bell curve problem), because this one degree is how much temperatures have risen at a level of about 1.5 metres above the ground. This is 1% of the problem. Ninety three percent of the extra heat is going into the oceans, and this is what matters. Water takes more space when it’s warmer, so sea levels are rising. The icecaps are melting, so they’re rising even more.

Steffen moved on to how this affects us in south east Australia. Due to that Bell curve effect, those extremely hot days that used to occur 3-4 times a year are now occurring 30-40 days of the year. Heatwaves, hot periods of 3-4 days in a row, are getting longer and are starting earlier in the season. Our hottest days are getting hotter. In 2014 Adelaide sweltered through five days in a row over 42 degrees.

The Macarthur Forest Fire Danger Index (MFFDI), Steffen told us, was developed by the CSIRO in the 1960s. It is used to predict the threat of bushfires using temperature, humidity and wind measurements and factoring in the condition of the vegetation. Scientists used the conditions at the onset of the 1939 Black Friday fires in Victoria – the worst Australia had seen by the 1960s – to set the “worst-case” 100 point mark. Jump forward 40-odd years: the index on Victoria’s Black Saturday fires in 2009 was calculated to be closer to 200.

Thirty-eight weather stations have been measuring the Macarthur Index in Australia for the last 40 years. Sixteen of them have shown a significant increase in high fire danger days in that time, and all of them are in south-eastern Australia. Some others are showing more modest increases; none are decreasing.

From bushfires, Steffen moved onto rainfall. It may surprise many of us that Australia is getting wetter. As the oceans warm, evaporation rates rise. And a warmer atmosphere can hold more moisture. But this rainfall has not been spread consistently over the country. While the northern parts are getting more rain, we’re getting less. The forecast is drier winters, longer dry periods, more droughts and, when it does rain, intense, heavy falls and floods.

Sea levels are rising because 93% of the extra heat in the system is going into the oceans, and water expands as it warms. And it doesn’t help that the icecaps are melting – there’s seven metres of extra sea water in the Greenland ice sheets alone.

Australia is particularly vulnerable to sea level rises because of the concentration of population and infrastructure on the coast. The twenty centimetres of sea-level rise we’ve seen in the last 150 years doesn’t seem like much, but every ten centimetres translates to a tripling in coastal floods. And we can expect a minimum of 40 centimetres by 2200 (and a possibility of a metre, depending on carbon emissions). Cities are usually engineered for the possibility of one-in-one-hundred-year” floods. But with a rise of 90 cm, those once in a lifetime events could be happening every day. Frequent flooding will make our coastal cities unviable long before they are totally inundated.

Infrastructure companies “have no time for sceptics” and are taking all this into consideration. The new runway at Brisbane Airport has been raised two metres, at an increased cost of hundreds of thousands of dollars, because the owners know if will save money in the future.

Amidst confusing global talk of emissions cuts of varying percentages against varying baseline years, scientists have recommended a really simple way of calculating emissions: “a carbon budget. It’s simple, clear, unequivocal, and you can’t game it.” We know the amount of carbon dioxide we can release, globally, with a 75% chance of remaining within the critical two degrees (even this rise will cause massive problems, but it’s considered manageable). In 2000 we had a trillion tonnes in the bank. We spent a third of that by 2013. So we have perhaps 26 years’ emissions left – if it’s “business as usual”. Then, nothing.

With so little time to act, every year is critical. “We’ve had a two year delay in Australia,” said Steffen. “Emissions were starting to go down with the carbon price but have crept back up [since it was abolished].”

If the carbon budget were adopted, it would be a matter of allocating emissions, and here’s where it gets tricky – politically. Steffen suggests it could done on a per capita basis, but Australia would already be in debt.

On the bright side, Steffen’s optimistic about the United Nations Climate Change Conference in Paris in November, where world leaders will aim to achieve a legally-binding, universal agreement on emissions reductions. He says the conference has already delivered, with Europe, the US and China laying ambitious targets on the table. Even India is talking about rolling out solar farms to power its thousands of villages and ceasing coal imports within two years (so much for Adani and the Galilee Basin). Steffen expects Australia to take Tony Abbott’s current low targets to Paris but to come back with the impetus for serious action under Malcolm Turnbull.

Steffen will be watching the Paris conference for further results such as rich countries planning to help poor ones, and a commitment to regular reviews of targets (a minimum of every five years, he says).

People complain that there’s too much talk of climate change in the media. But listening to Will Steffen in Bermagui that night, I wondered why we waste time talking about anything else.


An abridged version of this story was published in the November 2015 issue of The Triangle community newspaper.

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