Category Archives: Climate Science

The Prime Minister’s droughts

A version of this article appeared in the Southern Highland News, 2 April 2014. More articles from the CANWin column.

Image: Peripitus via Wikimedia Commons

Image: Peripitus via Wikimedia Commons

As the Prime Minister says, a cycle of drought and flooding rain is normal for Australia. Thirty years ago scientists worked out that the source of this natural cycle is not on land, but in the Pacific Ocean.

In a four-stage cycle called the El Nino Southern Oscillation (ENSO), warmth and moisture move back and forth between Australia and the Americas.

Westerly winds skim off the warm surface layer of the sea, transport it westward and pile it up to the north of Australia. This warm surface layer evaporates, the source of our La Nina rains. Then eastward winds flow back across the Pacific towards central America, bringing rain to Peru and Ecuador but leaving Australasia in El Nino drought.

This cycle has been going on for centuries; it’s the normal drought regime. Well done Prime Minister!

FloodedPlaygroundSignsBut our times are not normal, and the sooner you learn the difference, the better it will be for all of us. Man-made greenhouse warming is disturbing the natural balance. If we don’t all take the present global warming trend seriously, man-made greenhouse warming will double the frequency of extreme droughts. Prime Minister, it’s time to listen to the experts.

The experts will tell you that the surface mixed layer in the eastern Pacific gains more heat from man-made fossil fuel emissions than the west, where evaporation has a net cooling effect. This means that extreme droughts (such as 1982-83) are likely to return every 10 years instead of every 20. That leaves the food sources of the nation with not enough time to recover from the last severe drought.

So Prime Minister, why are you so heavily subsidizing dirty coal-fired power stations when renewable alternatives are available? Why do you allow such industries to off-load the costs of their pollution to other industries and the populace at large? Where is the level playing field for electricity generation? Why do you expect people to bear the cost of profligate spending on poles and wires for outdated, grid-based, 19th century technology?”

How about taking care of your grand-children’s future rather than your own?

Will Steffen: Science Meets Action

A version of this article appeared in the Southern Highland News, 5 March 2014. More articles from the CANWin column.

At CANWin’s first Speaker Night for 2014 Professor Will Steffen, of the crowd-funded Climate Council, gave a lot of information and a powerful call to action:

To stabilise the climate at a manageable level, most of the world’s fossil fuel reserves must stay in the ground.

The global carbon cycle

Professor Steffen showed that the carbon in fossil fuels – coal, oil, and gas – was locked away under the ground for millions of years. Right up till about 1850, that locked carbon could not affect the climate. The remaining carbon cycled naturally through the “earth system” – air, soil, oceans, plants and animals – but the total amount of carbon in the system stayed pretty much the same.

Then came the Industrial Revolution, when humans started burning fossil fuels. That sets free the carbon that was safely locked away. We are overloading the natural carbon cycle, and the unintended result is that we are changing the world’s climate.

That’s why energy efficiency and renewable energy are critically important. It’s also one, maybe even bigger than the risk to water and food, of many reasons to oppose coal and gas mining. In Professor Steffen’s words:

The evidence for climate change is overwhelming and clear. It is beyond reasonable doubt that the burning of fossil fuels is the primary cause.
We are already seeing the social, economic and environmental impacts of a changing climate, especially extreme events. The risks rise as climate shifts further.

Six things you can do

  • Learn as much as you can. CANWin’s website resources are one good starting point. Facebook can be an excellent source for breaking news. You’ll find free online courses at websites such as Spencer Weart’s excellent The Discovery of Global Warming is available as both a book and a website.
  • Connect with other people who understand that climate is critical. Local groups include CANWin, Lock the Gate, SHCAG, and Stop CSG Illawarra.
  • Just turn up to as many events as you can. Most events are publicised on Facebook, and the CANWin website has a calendar of local events.
  • Keep up those electricity, gas, and water saving habits. They really do help your wallet as well as the climate.
  • Switch to renewable energy or green power.
  • Support renewable energy projects, through organisations such as CANWin partner CORENA

Plus One

And a bonus action: Support the Climate Council. It’s one of Australia’s best sources of climate information that’s both understandable and reliable.

Boffins, Balls, and Brass Monkeys

We live at much the same latitude south as Texas USA is north. Yet this year Texas has been cold enough to freeze the balls off a brass monkey. How does that fit with the current global warming theory? Have the boffins got it all wrong?

Three wise monkeys, in brassWell no, they haven’t. Global warming turbo-charges the ocean and the atmosphere, generating heat waves here, freezing there, floods here, droughts there. One in a hundred year events, such as extreme bushfires in Australia, are now coming thick and fast. The weather is going haywire. The extra heat is destabilizing the global climate as if it has a fever.

Freezing weather in the southern states of the US, starts with changes in the Arctic. For ten thousand years the Arctic cold was kept in the north by a strong “Polar Front”. That’s a thermal barrier that normally keeps cold in the Arctic and warmth in the tropics, and incidentally drives the Jet Stream.

But the Arctic is warming, and the barrier between Arctic cold and tropic warmth is getting weaker. The Polar Front and the Jet Stream can now meander north and south, bringing Texans a taste of the Arctic and Greenlanders a taste of the tropics.

Those southward meandering loops of Arctic origin eventually pinch off from the jet stream to become separate storms. In the USA these storms sweep southeast across the midlands like fierce tops, spin-freezing unsuspecting Texas and leaving devastation in their wake.

Geology exam cartoonNo, the boffins have not got it wrong.; they predicted such weird events. It is global warming that allows the Arctic to cut loose and sweep across the States. There’s a saying: “To every complex problem there’s a simple answer – but it is usually wrong.” Climate science is a good example.

The good news for ordinary people is that we know how to live with complex science. Medical science, for example, is just as complex as climate science. When we have a health problem we go to medical specialists to find out what’s wrong and what to do about it.

That’s the role of specialists; they specialize, and they become boffins. We respect the advice of boffins because they have specialist knowledge and they’re more likely to be right than wrong.

Same thing with climate boffins. It’s betting against Nature to disregard their advice, and Nature always wins.

Bushfires and global warming

This article is adapted from Links between global warming and NSW bush fires, an article submitted by astone to the website of the Australian Research Council Centre of Excellence for Climate System Science. The full article, with references, is available there.

Bushfires are a natural phenomenon in Australia and a specific fire event as seen in the Blue Mountains in the last week is not caused by global warming.

RFS firefighterThe questions are more around:
• Is global warming increasing the risk of bushfires?
• Did global warming make the recent fires more likely?
• Is there a global warming link to the fires in the Blue Mountains?

Fuel Amount

Global warming does increase the amount of fuel. Elevated CO2 acts as a fertiliser and increases net primary productivity. So far as anyone knows, this effect is not sustainable over the long term due to limits imposed by nutrients. The fertilisation effect works in a farmer’s greenhouse where CO2 is elevated because the farmer also waters and fertilises the crops. We do not water or fertilise native bush.

CO2 Concentration

There is evidence that the Earth’s biosphere is sucking up more CO2 now than in the past, but failing to keep up with the increase in human emissions (Raupach et al., 2008). Whichever way you consider the system, increased CO2, if absorbed into the biosphere, must increase the amount of fuel. Therefore, increased CO2, linked to increased activity by vegetation, has increased fuel loads. This need not lead to more fires, but it means that if a fire occurs then there is more fuel to burn.


While there has been low rainfall over the last 3 and 6 months this is not particularly unusual and it is not possible to prove that the low rainfall has any global warming link. That is, the low recent rainfall cannot be shown to be linked to global warming. This does not mean it is not. It might be, but it might not be, and we cannot say anything more definitive than that. The short story is that global warming explains, to an important degree, observations of warming over Australia and global warming increases the risks of very warm summers and very warm winters a great deal.

Vegetation Dryness

There is a reasonable link between how dry the growing trees are and global warming which we cannot currently put numbers on, but at the very least means no one can say no link exists. So, it is very likely that as a consequence of the unusually hot summer, and the unusually warm winter, the landscape was unusually dry and a natural feedback that cools was switched off. Therefore, the question is, was the last summer and winter unusually warm because of global warming because if it was, then there is a legitimate link between global warming, warmth, and dryness. The short story is that global warming explains, to an important degree, observations of warming over Australia, and global warming increases the risks of very warm summers and very warm winters a great deal.


The risk for fire is linked to temperature, humidity, wind and dryness. One way to link these together is to use the McArthur Forest Fire Danger Index (FFDI). Clarke et al. (2012) analysed observations from high quality stations from the Bureau of Meteorology and calculated the FFDI from 1973 to 2010. There is an upward trend overall in FFDI. Most individual stations show an upward trend. No stations show a downward trend. In short, the risk of fire, as measured by FFDI, has increased since 1973 over NSW.

BurntOutTheir results suggested a doubling in risk of extreme bushfire risk by 2050. In short, so far as I know, no study has ever found that fire risk will reduce, or stay the same, in the future; every study points to increasing risks.


Outstanding risk minimisation by emergency services, changes in individual preparedness, improved weather forecasting by the Bureau of Meteorology, better building codes, new fire fighting technologies and a considerable and sustained effort by professional and volunteer fire fighters have all helped reduce the vulnerability of settlements in the Blue Mountains to fire. However, if we continue to drive climate through emissions of greenhouse gases, the risk of fire and associated losses will continue to grow.

Failure to accept a link between global warming and fire risk means not reducing the climate linked risk. It therefore leaves all management of the risk to NSW state agencies and mitigation by Rural Fire Service employees and volunteers. So, the NSW Premier Barry O’Farrell was right in noting a link between climate change and bush fire risk.

Predictions and events

A version of this article appeared in the Southern Highland News, 25 September 2013, under the title “Not an exact science”. More articles from the CANWin column.

Prediction is very difficult, especially about the future. Niels Bohr

Melting arctic ice, drowning civilisationA great big report is coming out this week. It’s called “Climate Change 2013: The Physical Science Basis”, and it’s been prepared by “Working Group 1 of the Intergovernmental Panel on Climate Change”, the IPCC. Three more massive reports will follow, one each from Working Groups 2 and 3, and then in October next year a synthesis report for policymakers that pulls them all together.

You might already have seen stories in the media suggesting that this first report “admits” that earlier predictions were wrong. Here’s a tip: when a reporter or a blogger talks about an IPCC prediction, there’s probably something wrong with the story.

For example, a couple of weeks ago a story did the rounds about sea ice in the Arctic. The story was that the IPCC predicted that sea ice would be gone by 2013, and instead it increased. There’s something wrong with both parts of that story.

Sea ice is frozen sea water. It grows in winter and melts in summer. In the northern summer of 2012 the Arctic sea ice melted to the lowest amount on record. In the summer just ended it melted to the 6th lowest amount on record. That’s more than last year, but still less than any year before 2005. It’s also 70% less than in the 1980s. Funny kind of increase!

The second problem is that the so-called IPCC prediction never happened and never would. Such a precise prediction would be like a life insurance company predicting the exact date of one person’s death. Insurers work with probabilities and uncertainty, and so does the IPCC.

When we think about how long we can expect to live, we need to remember that it depends partly on what we do in the time we’ve got left.

When we read about predictions in the new report, we need to remember that what happens to the Earth’s climate depends largely on what humans do from now on about greenhouse gases.

You’ll be able to see the report for yourself, starting with the summary for policymakers, which will be available from 30 September at

Warmer world = Wilder weather

Updated, 12 July 2013
Clive doesn't like cold weatherOur friend Clive doesn’t like cold weather.

“If the world is getting warmer,” he croaked, “How come there’s frost outside my pot?”

“It’s winter Clive,” we pointed out. He wasn’t impressed, so we showed him this terrific video from the ABC TV program Catalyst. It explains why the warmer world means unusual blizzards, as well as droughts, floods, and record-breaking heatwaves.


You can read the transcript and discussion at the Catalyst story page.

Open-minded frog that he is, Clive watched the video and shared it with some froggy friends in the Northern Hemisphere.

Candlestck chart of a rising stockmarket trend

A rising trend can have short-term falls.

“I’m only complaining about frosts,” he told us. “I understand trends. I didn’t say there are blizzards in Berrima.”

True enough. And good to know Clive understands that global warming doesn’t affect every part of the world in the same way: the warmer world means different wilder weather down under.

But we’ll have that conversation another day.

What’s Up With The Weather?

Rainfall12_13TotalNSWSouthern Highland News, 12 June 2013, Author Lou Flower. More articles from the CANWin column.
“Climate is what you expect; weather’s what you get.” As this year’s warm autumn ended, Dr Blair Trewin came to Moss Vale to tell us whether the weather we’re getting now is the weather our grandparents expected.

Dr Trewin’s speciality is analysing long-term Australian rainfall and temperature records. Because early information is patchy, the reports we see of record-breaking heat or rainfall refer to about 130 years of measurements – back to the days that our grandparents might have heard about from their grandparents.

Dr Trewin showed charts and maps that reveal patterns and variations in the data, both across the continent and in our own area. One example he showed was for rainfall in Moss Vale. The record shows that for over a century rainfall for Moss Vale varied with the seasons and with the El Nino / La Nina cycle, but after 1990 it’s gone down by about 10%. The main change is that there have been fewer months with more than 200mm of rain. These heavy rainfall periods are important for water storages downstream, so this trend is closely watched.

Rainfall12:13TotalOzNation-wide the records reveal two ways that the pattern of hot and cold weather has been shifting since around 2001. First, there are more new Australian records for high temperatures than for low. Second, heatwaves are getting longer and hotter.

At the end of his talk Dr Trewin answered a wide range of questions from the audience, who clearly enjoyed the chance to ask an active climate scientist about his work. Few people would expect someone who spends most of his time on mathematics to have a personal project to visit every Reference Climate Station from far southern Tasmania to Kalumburu.

Dr Trewin is a senior climatologist with the National Climate Centre section of the Australian Bureau of Meteorology. His talk was jointly arranged by CANWin and Council. It was the first in Council’s week of events dedicated to World Environment Day, and part of CANWin’s ongoing series of public speaker events.

It’s summer! It’s hot! What’s causing Australia’s heat wave?

Republished from The Conversation of 18 January 2013

Australia has started 2013 with a record-breaking heat wave that has lasted more than two weeks across many parts of the country. Temperatures have regularly gone above 48°C, with the highest recorded maximum of 49.6°C at Moomba in South Australia. The extreme conditions have been associated with a delayed onset of the Australian monsoon, and slow moving weather systems over the continent.

Swimming in waterhole

Australia has always had heat waves, but the current one is far from typical

Australia has always experienced heat waves, and they are a normal part of most summers. However, the current event affecting much of inland Australia has definitely not been typical.

The most significant things about the recent heat have been its coverage across the continent, and its persistence.

It is very unusual to have such widespread extreme temperatures — and have them persist for so long. On those two metrics alone, spatial extent and duration, the last two weeks surpasses the only previous analogue in the historical record (since 1910) – a two-week country-wide hot spell during the summer of 1972-1973.

A good measure of the spatial extent of the heat is the Australian-averaged maximum daily temperature. This is the average of the highest daily temperature of the air just above the surface of the Australian continent, including Tasmania. The national average is calculated using a three-dimensional interpolation (including topography) of over 700 observing sites each day.

On Monday and Tuesday last week (January 7 and 8) that temperature rose to over 40°C. Monday’s temperature of 40.33°C set a new record, beating the previous highest Australian daily maximum of 40.17°C set in 1972. Tuesday’s temperature came in as the 3rd highest on record at 40.11°C.

This map of temperatures shows just how much of the country experienced extremely high temperatures, with over 70% of the continent recording temperatures in excess of 42°C.

BoM temperature map

Highest daily maximum temperature during the first two weeks of January (Australian Bureau of Meteorology)

And it’s not like these sorts of days occur that often. The records set last week sit between two and three standard deviations above the long-term January mean of 35°C.

Perhaps more unusually, the Australian mean temperature (representing the average of the daytime maximum and night-time minimum) set record high values on both days at 32.22 (January 7) and 32.32°C (January 8), that were well above the previous high of 31.86°C, set in 1972.

However, it is really the duration of this extreme heat wave that makes it so unusual, and so significant in terms of impacts.

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