Are the tornadoes in the USA, or the floods in Queensland and Victoria, or the record drought in southwest Australia, or the Russian heatwave of last year or western Europe in 2003, or Black Saturday, anything to do with global warming?
It’s a big question, with a complicated answer. So let’s start with heatwaves.
The last decade has seen record high temperatures in many parts of the world, including Europe in 2003, southeast Australia in early 2009, and Russia in 2010. Some of the recent temperatures have absolutely smashed previous records, not just broken them.
For instance, the new record daily maximum temperature established in Melbourne, Australia on Black Saturday, 7 February 2009, was more than 3˚C hotter than the previous record Melbourne February temperature (and nearly a degree hotter than the previous all-time record high temperature).
Later that year, at Windorah in western Queensland, the record temperature for August was broken six times in a single month.
Before 2009, the temperature in August at this station had never reached 35˚C. This temperature was exceeded seven times in August 2009 and a new record August maximum temperature of 38˚C was set, a full 3.1˚C higher than the previous record.
And there are many more examples like Windorah. In November 2009, 41% of NSW set record high November temperatures, in the one month.
Heatwaves are also setting new duration records. The week before Black Saturday, Melbourne saw three days in a row with temperatures above 43˚C. Previously the city had never recorded three consecutive days exceeding 42˚C.
The previous year, in March 2008, Adelaide had 15 days in a row hotter than 35˚C. Before 2008 the Adelaide record run of hot days was only eight days.
Record runs of hot days were again experienced in Adelaide in January/February 2009 and again in November that year.
In Sydney the first week of February 2011 saw seven consecutive days above 30˚C, a heatwave two days longer than had ever been seen in the 152 years of data. A new Sydney minimum temperature record was set, fully one degree above the previous all-time record.
Almost everywhere where the Bureau of Meteorology has good data, we are seeing more high temperatures and longer warm spells.
Of course, we still set new cold records, even in a period of global warming. But research at the Bureau of Meteorology has shown that over the last decade hot records are being set more than twice as frequently as cold records are being broken.
And it is not just Australia.
In Russia last year, and in western Europe in 2003, “mega-heatwaves” meant that their summer was most likely hotter than any summer for at least 500 years.
More than half of Europe broke the 500-year record twice in the one decade. Both these heatwaves caused tens of thousands of deaths. The last decade has truly been the decade of unprecedented heatwaves.
None of these heatwaves was caused by global warming. They were the result of naturally occurring weather events.
In the case of Melbourne such events lead to strong, sustained northerly winds from the interior of the continent. Similar weather systems were causing high temperatures centuries before we started to affect the composition of the atmosphere by increasing emissions of greenhouse gases such as carbon dioxide.
But the warming caused by our carbon dioxide emissions is pushing temperatures in these weather events to new extremes.
Other extremes are more difficult to link to global warming. The Queensland floods, for instance, were the result of a record-breaking La Niña event, a natural phenomenon that has been causing heavy rains and widespread floods in Australia for at least thousands of years.
Has global warming exacerbated the La Niña, or its impact on Australia? Perhaps, but the evidence is pretty thin, as yet.
Similarly, with the USA tornadoes – we just don’t know if there is a link. And we don’t even know if this is because the data are poor, or our analyses are insufficient, or if there really isn’t much of an influence of global warming on these sorts of extreme events.
We don’t even know if more and better research will answer this question.
But the evidence is clear for hot temperatures and heatwaves – humans are making these worse. And without political agreement to restrain greenhouse gas emissions we can look forward to worse heatwaves in the future.
We don’t cope well with heatwaves, even now. Mortality increases substantially on hot days, as do ambulance callouts and infrastructure damage.
So governments around the world are increasing their efforts to deal with the ever-increasing problems caused by heatwaves, by introducing and improving systems for alerting the vulnerable to an impending heatwave, and providing support to ensure we improve our ability to cope.
The alert systems won’t save everyone, but they do make a difference. And if by some fluke the world doesn’t continue to warm, if the fairies at the bottom of the garden manage to offset the increases in greenhouse gases, these new heatwave alert systems will still save lives. That’s not such a bad thing.
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Comments (8)
Marc Hendrickx
(Geologist)
Seems to be a contradiction here Neville:
"None of these heatwaves was caused by global warming. They were the result of naturally occurring weather events."
"But the evidence is clear for hot temperatures and heatwaves – humans are making these worse."
Life expectancy in Australia has increased from 70.8 in 1960 to 81.5 years in 2009 (see link below). Seems you are missing the bigger picture as to whether humans are making things worse or not.
http://www.google.com/publicdata?ds=wb-wdi&met_y=sp_dyn_le00_in&idim=country:AUS&dl=en&hl=en&q=life+expectancy
Mark Duffett
(logged in via Facebook)
I can't see the contradiction, Marc. I understand Neville (and the evidence he presents) to be saying that global warming is exacerbating heat waves in their duration and intensity, not necessarily their frequency.
I take your point about human progress, but would also point out that we can have our low-carbon cake and eat it (i.e. have our life-extending prosperity) too, if we avail ourselves of the abundant energy afforded by nuclear power.
John Nicol
(logged in via Facebook)
Neville. I am not sure what the time line is for the records you claim were broken in Windorah. Having lived much of my early life in western Queensland, 35 C (95 F) in August does not seem to be any where near extreme weather to this simple soul. I don't suppose there were a lot of thermometers around the west in the 1800s. Perhaps you could let us know more detail if you wish to substantiate the case. I am prepared to accept what ever the real records say. and withdraw my comment unreservedly.
Mark Duffett
(logged in via Facebook)
http://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=40&p_display_type=dataFile&p_startYear=&p_c=&p_stn_num=038024
This record (of extreme temps) only goes back to 1963, though Windorah Post Office has been recording some sort of observation since 1887. Not sure what's happened there, though I would guess some sort of instrument or procedure change pre- and post-1963.
Marc Hendrickx
(Geologist)
According to BOM, the older records for Windorah relate to rainfall. Max temp readings at Windurah commenced in 1963s. If climate is 30 years of average weather then it's hard to say much about climate change based on the weather in Windurah. Indeed the station is not part of the BOM's high-quality climate site network. This a good example of cherry picking the data on Neville's part.
http://reg.bom.gov.au/climate/cdo/metadata/pdf/metadata038024.pdf
Andrew B. Watkins
(Manager of Climate Prediction Services at Australian Bureau of Meteorology)
Cherry picking is when you use a single unsupported case to support your hypothesis, whereas Neville has not only given several cases (e.g., Melb which has data back to 1856,) but his statements also correspond with the published literature. I suggest you do some reading Mark.
Start with:
http://www.springerlink.com/content/j488604372402531/
then check
http://reg.bom.gov.au/amm/docs/2007/alexander.pdf
and consider how it relates to
http://onlinelibrary.wiley.com/doi/10.1002/joc.1730/abstract
All the best with your research Mark.
Felix MacNeill
Felix MacNeill (logged in via email @grapevine.com.au)
Couldn't agree more Mark - except I think it's not so much an option as a necessity: if we DON'T go low-carbon, there won't be much of a cake left to eat.
Nonetheless, as you say, we don't have to 'live in caves' to reduce our negative impact on the environment. We will need to modify our lives and our economies a bit - it won't be free to make the necessary transition, but it will be affordable, and failing to do so will the the real unaffordability.
Paul Richards
"None of these heatwaves was caused by global warming. They were the result of naturally occurring weather events."
Anyone who does understands and or like me has been aware of this issue over many decades, sees the statement in context. My only concern is writing to a level of awareness outside the field of understanding,it can sound confusing.
The whole climate change issue is an escalation of natural events, that's the point.
Picking which one and where it occurs is hard to predict. That…
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