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Scientists find human fingerprints all over Australia's hottest year on record

Posted on 3 October 2014 by Guest Author

Australia had a hot one in 2013 – a real record breaker.

We started off with a heat wave that made January 2013 the hottest month on record that was part of the hottest summer on record that then became the hottest year on record.

Meteorologists and climatologists looking at records tend to express things by “anomalies” – how far above or below the long-term average is a particular temperature.

September 2013 had all the anomalous bells and whistles you could muster, managing to break above the long term average by 2.75C – a departure greater than any other month on record going back to 1910.

But how much of the temperature rise from that remarkable year was actually down to the extra CO2 in the atmosphere that’s caused the planet to continue to build up heat? Did we leave our dirty fossil fuel fingerprints anywhere?

Here’s one answer (actually there are several, but we’ll start with one).

Climate scientists Dr Sophie Lewis, of the Australian National University, and Professor David Karoly, of the University of Melbourne, ran two groups of computer models for a study into Australia’s scorching 2013.

In one group, they included the extra carbon dioxide in the atmosphere being added at the rates they are now. In another group of models, they left out the human contribution.

They found that on average, the computer models with current levels of carbon dioxide managed to reproduce the temperatures comparable to that scorching year of 2013 every six years.

For the computer models without the added greenhouse gas emissions, they got a year as hot as 2013 only once in more than 12,000 years.

So was it global warming what done it? I asked Dr Lewis.

Instead of focusing on blame, it is more useful to understand the contributing factors to an event, such as natural variability and greenhouse warming. In the case of Australia’s record hot year, anthropogenic influences were a big contributor, to the point that the temperatures we experienced would have been virtually impossible without greenhouse gases. This doesn’t mean that natural variability isn’t important too.

There is one line of thought that all the weather and climate events we have experienced have occurred in a hotter, wetter environment caused by greenhouse gases. Because of this, we play a part in everything.

Another is the old stock statement that because many factors interact in complex systems, we can’t separate out human influences from natural climate variability.

I don’t think either is particularly useful for helping to understand the extremes we are experiencing.

Statements like “no single event can be blamed on global warming” aren’t useful. They prevent us from understanding how climate change is influencing what we experience.

Lewis’ study was one of 22 in a special edition of the Bulletin of the American Meteorological Society that looked at potential human influences on 16 extreme weather events across the globe.

Five of the 22 studies looked at Australia’s record heat of 2013.

One study, led by scientists at the US Government’s National Oceanic and Atmospheric Administration, looked at Australia’s record-breaking temperature “anomaly” in 2013 for average temperatures – that’s 1.72C.

Then they ran a series of computer models. They then sliced up the 1.72C into chunks and found that just under half of the temperature increase (0.81C) was down to human emissions.

Another study led by Australia’s Bureau of Meteorology looked in particular at that hot September where the maximum temperatures were 3.32C above the long-term average (what they were between 1961 and 1990).

Human influences played “an important role”, the study said, and up to 15 per cent of the extra heat was down to the warming trend since the early 1980s.

Another study found that the risk of Australia experiencing more heat waves had now tripled when compared with an atmosphere without the added greenhouse gases.

Finally, the fifth study looked at the relationship between drought and maximum temperatures. Before 2013, the hottest year in terms of the maximum temperatures was 2002.

Click here to read the rest from Graham Readfearn at The Guardian

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Comments 1 to 19:

  1. The official measurements of temperatures in Australia are made by the Bureau of Meteorology (BoM) which is currently under scrutiny for some practices, which it stoutly defends, that are claimed to:

    Turn cooling trends into warming trends

    Disregard early temperature records that show 2013 may not have been the hottest year ever.  These claims have been made by Graham lloyd writing in the Australian.  Senator Simon Birmingham who has responsibility is to set up independent technical advisory group by end 2014.

    Whether the criticism of the BoM is justified has yet to be established, although i suspect it is ill founded.  That said however, it might, just might, be somewhat premature to make claims that 2013 was Australia's hottest year ever as data prior to 1910 may show this not to be the case.  Whatever, the public perception of the BoM is less favourable than previously was the case.

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  2. My apologies.   The last line of my previous post should read "Whatever, the public perception of the BoM might be  less favourable than previously was the case".  

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  3. Ashton: If you don't trust the BoM adjustments, Berkeley also produce a record for Australia, working independently from the raw data. Their results only run to Oct 2013, but the 12 month period to Oct 2013 was the hottest of any consecutive 12 month period on record.

    Raw data are available from GHCN, ISTI, Berkeley and BoM (Nick Stokes provides more convenient access to the BoM data here). Adjsted data are available from GHCN, Berkeley, BoM and CRU.

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  4. Ashton @1, the Bureau of Meteorology is under scrutiny because:

    1)  A purported scientist claimed one BOM adjustemt which eliminated a falling trend cannot have been correct because a nearby station had a similar trend half a decade later.  (I live in the area.  I can tell you it does not take five odd years for weather to move the less than 100 miles from the one station to the other.)

    2)  Another purported scientist claimed that a station move claimed to have occurred by BOM cannot have happened because he periodically visited the general location thirty years after the apparent site move and therefore knew that no such site move had occurred.  He mentioned that he worked there.  He did not mention the timing.  (In my opinion that makes him a deliberate liar on this matter.)

    3)  A purported journalist who is always quick of the bat with a pro "skeptic" story, but leaves coverage of mainstream science to other journalists in his paper, reported the above in breathless tones while failing (or not reporting) the salient facts about timing, and declining to report when the BOM published online the proof of the station move referred to in (2).

    4)  A political hack closely associated with the current Prime Minister who is a known climate change denier with no scientific qualifications (or understanding from what he writes).

    In other words, the scrutiny of the BOM is entirely politically motivated by people who do not like the possibility of positive policy on climate change.  Its purported basis has zero scientific merit.

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  5. KevinC please read what I actually wrote. I did not express a personal opinion on  the BoM readings but commented on the opinions of others.   In fact I specifically noted that I thought the criticism of the BoM was likely to be ill founded.

    Tom Curtis:  virtually everything about climate change/global warming in Australia is now politically motivated so why should the BoM be exempt from it?  Did you think Rudd and Milne and Gillard were not politically motivated?  Rudd rapidly backed away from the "the greatest moral challenge etc"  when opinion polls showed it to be politically damaging in the 2010 election year. Was this "positive policy" on climate change?  The Green's  sided with the LNP in the Senate to defeat the CPRS.  Positive policy?  Julia Gillard total backflip on the ETS  was solely to gain support of the Greens to prop up her government.  That was positive policy but for purely opportunistic political reasons as just prior to the election Gillard had said "There will be no tax on carbon etc"  a promise entirely devoid of positive policy on climate change.  With examples such as these  is it any wonder that Abbott is politically motivated also?  It would be more remarkable if he wasn't.  Many of those who think something must be done about climate change seem entirely oblivious to the fact that, despite protest marches and general angst in the chatteratti, a significant minority of Australians do not want action as it will, at least the perception is that it will, increase the cost of their power.  After all Abbott came to power with a thumping win on a policy that he would axe Gillard's ETS.   A policy  he has successfully implemented.  And outside Australia the problems with global actions on climate change are fairly well summed up in The Diplomat (

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  6. Ashton, you're not making a convincing case but in fact reinforcing Tom's arguments. Politicians are politically motivated. I had no doubt about that. People have mistaken perceptions about the state of climate change, and the consequences of mitigation policies. No doubt there either. A certain current of thought has managed to load the word "tax" with the same emotional charge that the word "devil" enjoyed for centuries. Politicians working against this current of thought have to navigate the public opinion landscape created by the skilled mind manipulators employed by that current of thought.

    You do not show that scientists currently working in the field are politically motivated. You seem to add to the idea that the attacks on the BoM are politically motivated. You say nothing about the data. You confirm that any negative perception of the BoM is new thing caused by politically motivated attacks from people who seem to intentionally mislead the public or have no clue about what the subject. The rest of your post is about details in Australian political games and steer far enough from the OP to attract moderation.

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  7. Any interested readers should reread Ashton's responce to me.  It will demonstrate conclusively that:

    1)  He is not here because of concerns about science;

    2)  He is merely tarnishing the name of scientists because he does not like the science; and

    3)  He has nothing substantive to add to the discussion.

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  8. Tom Curtis   Globally, the science (according to NOAA, says 2013 was the fourth hottest year since records began in 1880.  Is the fact that 2013 was the hottest year in Australia really of any global significance or just of interest to Australians?  

    This is what Skeptical Science had to say about the hottest year in the USA


    "Climate change skeptics like to point to 1934 in the U.S. as proof that recent hot years are not unusual. However, this is another example of "cherry-picking" a single fact that supports a claim, while ignoring the rest of the data. Globally, the ten hottest years on record have all occurred since 1998, with 2005 and 2010 as the hottest.

    The fact that there were hot years in some parts of the world in the past is not an argument against climate change. There will always be regional temperature variations as well as variations from year to year."

    These comments seem to apply equally to the claim "2013 was Australia's hottest year"  Is that claim just "cherry picking a single fact that supports global warming?  If not, why not?


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    Moderator Response:

    [Rob P] - A cherry-pick is where one deliberately chooses a a small piece of evidence that is completely at odds with the full body of evidence. It is a logical fallacy.

    Australia experiencing its hottest year ever recorded in 2013 is consistent with the full body of evidence - the Earth is warming in a global, but not uniform, manner. The contiguous USA experiencing its warmest year ever recorded in 2012 is also consistent with the full body of evidence.

    Hope this helps.

  9. Ashton, as you bring it up, the contiguous United States' hottest year was 2012, with 1934 only ranking fourth:

    More importantly, as we don't want to cherry pick, the world's hottest year was 2010, with no year prior to 1979 warmer than any year after 1996 :

    Back on topic, your response shows categorically that you have rather missed the point.  The article is not simply claiming that "Australia was very hot in 2013, therefore global warming is true".  It is pointing out that specific studies showed that Australia was very hot in 2013 because of global warming.  To quote one example:

    "In one group, they included the extra carbon dioxide in the atmosphere being added at the rates they are now. In another group of models, they left out the human contribution.

    They found that on average, the computer models with current levels of carbon dioxide managed to reproduce the temperatures comparable to that scorching year of 2013 every six years.

    For the computer models without the added greenhouse gas emissions, they got a year as hot as 2013 only once in more than 12,000 years."

    Quoting further:

    "Another study found that the risk of Australia experiencing more heat waves had now tripled when compared with an atmosphere without the added greenhouse gases."

    And another:

    "The study found that the risk of Australia getting a year of maximum temperatures hotter than 2002 is 23 times greater than it was in the late 19th century. There was an at least seven-fold increase in the risk of Australia getting a combination of extreme heat and drought occurring at the same time."

    The article above is about all the various studies, and one indeed was a straight forward attribution study.  That single study (mentioned in just two sentences) can be interpreted as being about evidence that global warming is not only occuring, but is man made.  But being personally at risk of the sevenfold increase of a combination of extreme heat and drought (as an Australian), so far as I am concerned the article is really about impacts.

    We know that global warming is happenning and is anthropogenic.  The Australian year of 2013 shows us that that has more than unpleasant consequences.

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  10. This is not a simple concept, because it involves thinking in terms of distributions of probabilities, rather than in terms of logical propositions. This is an alien way of thinking for all of us.

    Roughly speaking the conceptual problem is that it involves 'thinking in parallel' - holding and weighing many hypotheses against the data at the same time. This involves what are historically called 'inverse probabilities' which are particularly confusing.

    So the concepts are hard. But I'll take a shot at explaining the application here:

    1. One year of extreme global temperatures is not proof of global warming.
    2. One year of extreme local temperatures is not proof of global warming.
    3. However, both of these do provide information of a form.
    4. Evaluating information of this form of information is rather difficult. It is an area of active research.
    5. There are two questions which can be meaningfully asked: "How much more extreme was this event due to global warming", and "How much more probable was this event due to global warming".
    6. Readfearn reviews 5 recent articles on this kind of analysis concerning the 2013 temperatures in Australia.
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  11. A short time ago I put up a post, or at least I thought I did but admittedly didn't check thoroughly.  It may have been removed by the moderator for any one of a number of reasons but I'm not sure it was.  In any event what I posted referred to Tom Curtis's statement "It is pointing out that specific studies showed that Australia was very hot in 2013 because of global warming."  I suggested that according to that argument global temperatures in 2006 -2009 were cooler than 2005 and in 2011 and 2012 were cooler than 2010 because of global cooling.  To me that seems a perfectly reasonable conclusion based on the argument advanced by Tom Curtis. Of course I realise this isn't the case but it is a logical follow on from Tom Curtis's statement.   I don't think this post is offensive or off topic but then I'm not the moderator so if it is deemed to be so then my apologies to all especially Tom Curtis.  

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  12. Your post was indeed posted, and mine was written in reply to it. While I was writing my reply your was deleted by a moderator.

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  13. "virtually everything about climate change/global warming in Australia is now politically motivated so why should the BoM be exempt from it?"

    Politicians are politically motivated but scientists? This is pure projection. Are you seriously claiming that BoM scientists are tampering with the record for some dark political purpose? This is conspiracy ideation.

    I do contract science for my government where the paymasters fervently hope that the money spent will lead to new prosperity. Do you seriously think that this means me and my colleagues would falsify results to please our paymaster? Such a scheme would be pointless because reality wins. Ditto for climate science.

    It is absolutely absurd that there is political shennigans over reality and cause of climate change. The political divide should be over different approaches to dealing with that reality. Instead we have people denying that reality instead because the only solutions on offer dont fit their ideology. They should be thinking of something that does fit instead of this stupid attack on scientists. 

    So Ashton, given this from BoM on Rutherglen, what do you thoughts on   Marohasy and LLoyd now?

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  14. scaddenp   Nowhere in my original post did I refer to scientists but to the way Australian politicians and the Australian media spin climate change.  However, I do accept that my phrase "virtually everything" was inaccurate and that being so, I appreciate why you commented as you did.  

    No, I certainly don't think scientists are politically motivated although it would be a brave person who said none of them are.  As a retired  university academic who conducted research for many years, I am paid by the federal government and also by government granting bodies such as the ARC.  No scientist that I know would falsify results for any reason at all,  let alone "just to please their paymaster".  But every, well virtually every, utterance from a scientist about the climate  is spun by the media and even by  blogs.  This site publishes findings that support anthropogenic climate change/global warming but is critical of scientists that do not.  An  example is your question "So Ashton, given this from BoM on Rutherglen, what do you thoughts on Marohasy and LLoyd now?"

    As I'm not sure to which particular  comments from Dr Marohasy and Mr Lloyd  you refer, I'm not really able to answer your question constructively.  And on the sceptic or if you prefer, denier, side,   Watts Up With That publishes findings that do not support anthropogenic climate change/global warming   and is critical of scientists that do.   A prime eample of this being the way Dr Michael Mann is referred to on that site.  

    And because I'd really like to know the answer, why, given that human CO2 emissions are relentlessly increasing, were global temperatures in 2006 to 2009 and 2011 and 2012 cooler than those temperatures in both 2005 and 2010.  Is the answer that this is due to natural phenomena and if so what were these phenomena?

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    Moderator Response:

    [TD] See "CO2 Is Not the Only Driver of Climate."

  15. Kevin,

    In a more intuative way can we say that the Theory of Global warming is supported by the occurance of a record hottest year every 5-10 years.  The hypothesis of cooling is contradicted by the fact that 2006-2009 and 2011-2012 were warmer that all years before 1998.  Everyone here was alive  well before 1998 so every year is warmer than when we were all born.  When you consider the fact that weather has a lot of random variation (a fact that every five year old knows from personal experience), we do not expect every year to be record hot.

    According to Tom's link at 9 we now expect a year comparable to the record hot year every six years (!!!).  With continuing heating those years will be likely to exceed the record hot year.  Tom's graph also shows the USA having three record or near record years in the past ten years, consistent with the Australian projections.  Global records have occured in 1998, 2005, 2010 and are looking strong for this year.  Since we are emitting more and more CO2 those will be hotter and hotter.  Pray that politicians recognize the issue sooner rather than later.

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  16. Ashton, I was referring to your comment "it may be that those questioning the integrity of the BoM might, just might, not be miisguided conspiracists judging from this paragraph from Lloyd's piece"   from here. It would now seem that indeed they are misguided conspiracists wouldnt you agree?

    As for Watts, really! I am disappointed that a retired academic can take seriously "findings" at WUWT. CO2 falling as snow in Antarctica? Sks exists to explain what the science actually says in the face of misinformation sites like that. There is no problem at all with peer-reviewed papers that critical of climate theory. Sadly for us, (since who wants AGW to be true) there is a distinct lack of papers that have robust results.

    As to having your questions answered, the obvious first step is actually read the IPCC WG1 report which unsurprizingly answers your question. You dont have to agree with its assessment but you can at least use it as an index to the published science on the topic rather relying on blog "scientists" like Tisdale and "Goddard". 

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  17. I just wish to note that Ashton (@11) misrepresents my comments to create a bizarre strawman.  The comment on which he based the strawman summarized studies, descriptions of several of which were immediately provided.  That context immediately demonstrated his "interpretation" of my words was false.  In particular, had his interpretation been correct, then every year after 2013 would have been warmer than 2002.  Yet I quoted the description of a study saying "getting a year of maximum temperatures hotter than 2002 is 23 times greater than it was in the late 19th century"  As in fact no years in the late nineteenth century, or indeed prior to 2002, had maximum temperature as high as 2002 (which was then an Australian record year), the probability of such a year in the late 19th century was of the order of 1% or less indicating a current probability >75% of maximum temperatures less than 2002.

    I regard Ashton's "misinterpretation" to have been deliberate, and another attempt to shift the topic after he had been comprehensively refuted (as he did with regard to BOM adjustments immediately after the initial responses to his having raised it.

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  18. My apologies Tom Curtis as I really don't deliberately try to misrepresent your comments to "create a bizarre strawman" and to be honest I don't know what this bizarre strawman is.  Nor do I deliberatyely misinterpret what you write.  I take your comments at face value and respond accordingly.  Apologies again but I don't understand your comment "In particular, had his interpretation been correct, then every year after 2013 would have been warmer than 2002."  

    I'm not sure why you 

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  19. Ashton @12, you represented me as making a claim that implied MGST would increase monotonically. That was not the case, and transparently not the case from what I wrote. You are not pretending that you made no such claim - which quite frankly makes me even more dubious of your honesty.

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