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Bushfires and extreme heat in south-east Australia

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Guest commentary by David Karoly, Professor of Meteorology at the University of Melbourne in Australia

On Saturday 7 February 2009, Australia experienced its worst natural disaster in more than 100 years, when catastrophic bushfires killed more than 200 people and destroyed more than 1800 homes in Victoria, Australia. These fires occurred on a day of unprecedented high temperatures in south-east Australia, part of a heat wave that started 10 days earlier, and a record dry spell.

This has been written from Melbourne, Australia, exactly one week after the fires, just enough time to pause and reflect on this tragedy and the extraordinary weather that led to it. First, I want to express my sincere sympathy to all who have lost family members or friends and all who have suffered through this disaster.

There has been very high global media coverage of this natural disaster and, of course, speculation on the possible role of climate change in these fires. So, did climate change cause these fires? The simple answer is “No!” Climate change did not start the fires. Unfortunately, it appears that one or more of the fires may have been lit by arsonists, others may have started by accident and some may have been started by fallen power lines, lightning or other natural causes.

Maybe there is a different way to phrase that question: In what way, if any, is climate change likely to have affected these bush fires?

To answer that question, we need to look at the history of fires and fire weather over the last hundred years or so. Bushfires are a regular occurrence in south-east Australia, with previous disastrous fires on Ash Wednesday, 16 February 1983, and Black Friday, 13 January 1939, both of which led to significant loss of life and property. Fortunately, a recent report “Bushfire Weather in Southeast Australia: Recent Trends and Projected Climate Change Impacts”(ref. 1) in 2007 provides a comprehensive assessment on this topic. In addition, a Special Climate Statement(ref 2) from the Australian Bureau of Meteorology describes the extraordinary heat wave and drought conditions at the time of the fires.

Following the Black Friday fires, the MacArthur Forest Fire Danger Index (FFDI) was developed in the 1960s as an empirical indicator of weather conditions associated with high and extreme fire danger and the difficulty of fire suppression. The FFDI is the product of terms related to exponentials of maximum temperature, relative humidity, wind speed, and dryness of fuel (measured using a drought factor). Each of these terms is related to environmental factors affecting the severity of bushfire conditions. The formula for FFDI is given in the report on Bushfire Weather in Southeast Australia. The FFDI scale is used for the rating of fire danger and the declaration of total fire ban days in Victoria.

Fire Danger Rating           FFDI range
High                          12 to 25
Very High                     25 to 50
Extreme                         >50

The FFDI scale was developed so that the disastrous Black Friday fires in 1939 had an FFDI of 100.

To understand the environmental conditions associated with the catastrophic bushfires on 7 February 2009, we need to consider each of the factors and the possible role of climate change in them.

Maximum temperature: This is the easiest factor to consider. Melbourne and much of Victoria had record high maximum temperatures on 7 February (2). Melbourne set a new record maximum of 46.4°C, 0.8°C hotter than the previous all-time record on Black Friday 1939 and 3°C higher than the previous February record set on 8 February 1983 (the day of a dramatic dust storm in Melbourne), based on more than 100 years of observations. But maybe the urban heat island in Melbourne has influenced these new records. That may be true for Melbourne, but many other stations in Victoria set new all-time record maximum temperatures on 7 February, including the high-quality rural site of Laverton, near Melbourne, with a new record maximum temperature of 47.5°C, 2.5°C higher than its previous record in 1983. The extreme heat wave on 7 February came after another record-setting heat wave 10 days earlier, with Melbourne experiencing three days in a row with maximum temperatures higher than 43°C during 28-30 January, unprecedented in 154 years of Melbourne observations. A remarkable image of the surface temperature anomalies associated with this heat wave is available from the NASA Earth Observatory.

Increases of mean temperature and mean maximum temperature in Australia have been attributed to anthropogenic climate change, as reported in the IPCC Fourth Assessment, with a best estimate of the anthropogenic contribution to mean maximum temperature increases of about 0.6°C from 1950 to 1999 (Karoly and Braganza, 2005). A recent analysis of observed and modelled extremes in Australia finds a trend to warming of temperature extremes and a significant increase in the duration of heat waves from 1957 to 1999 (Alexander and Arblaster, 2009). Hence, anthropogenic climate change is likely an important contributing factor in the unprecedented maximum temperatures on 7 February 2009.

Relative humidity: Record low values of relative humidity were set in Melbourne and other sites in Victoria on 7 February, with values as low as 5% in the late afternoon. While very long-term high quality records of humidity are not available for Australia, the very low humidity is likely associated with the unprecedented low rainfall since the start of the year in Melbourne and the protracted heat wave. No specific studies have attributed reduced relative humidity in Australia to anthropogenic climate change, but it is consistent with increased temperatures and reduced rainfall, expected due to climate change in southern Australia.

Wind speed: Extreme fire danger events in south-east Australia are associated with very strong northerly winds bringing hot dry air from central Australia. The weather pattern and northerly winds on 7 February were similar to those on Ash Wednesday and Black Friday, and the very high winds do not appear to be exceptional nor related to climate change.

Drought factor: As mentioned above, Melbourne and much of Victoria had received record low rainfall for the start of the year. Melbourne had 35 days with no measurable rain up to 7 February, the second longest period ever with no rain, and the period up to 8 February, with a total of only 2.2 mm was the driest start to the year for Melbourne in more than 150 years (2). This was preceded by 12 years of very much below average rainfall over much of south-east Australia, with record low 12-year rainfall over southern Victoria (2). This contributed to extremely low fuel moisture (3-5%) on 7 February 2009. While south-east Australia is expected to have reduced rainfall and more droughts due to anthropogenic climate change, it is difficult to quantify the relative contributions of natural variability and climate change to the low rainfall at the start of 2009.

Although formal attribution studies quantifying the influence of climate change on the increased likelihood of extreme fire danger in south-east Australia have not yet been undertaken, it is very likely that there has been such an influence. Long-term increases in maximum temperature have been attributed to anthropogenic climate change. In addition, reduced rainfall and low relative humidity are expected in
southern Australia due to anthropogenic climate change. The FFDI for a number of sites in Victoria on 7 February reached unprecedented levels, ranging from 120 to 190, much higher than the fire weather conditions on Black Friday or Ash Wednesday, and well above the “catastrophic” fire danger rating (1).

Of course, the impacts of anthropogenic climate change on bushfires in southeast Australia or elsewhere in the world are not new or unexpected. In 2007, the IPCC Fourth Assessment Report WGII chapter “Australia and New Zealand” concluded

An increase in fire danger in Australia is likely to be associated with a reduced interval between fires, increased fire intensity, a decrease in fire extinguishments and faster fire spread. In south-east Australia, the frequency of very high and extreme fire danger days is likely to rise 4-25% by 2020 and 15-70% by 2050.

Similarly, observed and expected increases in forest fire activity have been linked to climate change in the western US, in Canada and in Spain (Westerling et al, 2006; Gillett et al, 2004; Pausas, 2004). While it is difficult to separate the influences of climate variability, climate change, and changes in fire management strategies on the observed increases in fire activity, it is clear that climate change is increasing the likelihood of environmental conditions associated with extreme fire danger in south-east Australia and a number of other parts of the world.

References and further reading:

(1) Bushfire Weather in Southeast Australia: Recent Trends and Projected Climate Change Impacts, C. Lucas et al, Consultancy Report prepared for the Climate Institute of Australia by the Bushfire CRC and CSIRO, 2007.

(2) Special Climate Statement from the Australian Bureau of Meteorology “The exceptional January-February 2009 heatwave in south-eastern Australia”

Karoly, D. J., and K. Braganza, 2005: Attribution of recent temperature changes in the Australian region. J. Climate, 18, 457-464.

Alexander, L.V., and J. M. Arblaster, 2009: Assessing trends in observed and modelled climate extremes over Australia in relation to future projections. Int. J Climatol., available online.

Hennessy, K., et al., 2007: Australia and New Zealand. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, et al., Eds., Cambridge University Press, Cambridge, UK, 507-540.

Westerling, A. L., et al., 2006: Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity. Science, 313, 940.

Gillett, N. P., et al., 2004: Detecting the effect of climate change on Canadian forest fires. Geophys. Res. Lett., 31, L18211, doi:10.1029/2004GL020876.

Pausas, J. G., 2004: Changes In Fire And Climate In The Eastern Iberian Peninsula (Mediterranean Basin). Climatic Change, 63, 337–350.


399 Responses to “Bushfires and extreme heat in south-east Australia”

  1. 101
    Hank Roberts says:

    William, there’s nothing in what you quoted, nor in the whole article about a “claim to prove” — those are your words, not the author’s.

    The paper
    > does not claim to prove

    That’s true, and unremarkable. Do you understand this?

  2. 102
    Hank Roberts says:

    Ummenhofer et al. says toward the end:

    “To summarize Fig. 3, the sign of the rainfall anomalies over southeast Australia during pure La Niña and positive IOD events is highly
    variable, whereas El Niño years consistently result in dry conditions and negative IOD years consistently in wet conditions (see also Auxiliary Fig. 1).”

    “gip” — what’s the basis in the paper for the statement you make above (7:03am)?

  3. 103
    tamino says:

    Re: #95 (Greg)

    You started by saying (in #56)

    “Protracted drought”, “rainfall decline over Southern Australia”? Where’s that then?

    Popular delusions and the madness of crowds…

    I think you were trying to cast doubt on the reality and/or severity of drought, but now that that’s been refuted you want to make believe you were only talking about rainfall.

    And by the way, the Murray-Darling basin covers most of New South Wales and parts of South Australia and Victoria.

    You’re wrong about rainfall anyway, at least for Victoria (the subject of this post):

    http://tamino.files.wordpress.com/2009/02/vic.jpg?w=500&h=499

    http://tamino.files.wordpress.com/2009/02/vicanom.jpg?w=500&h=499

  4. 104
    William says:

    Hank #102
    You are correct. I amend my comment #83 to substitute “does not claim to answer the question whether an increase in fire weather is due to climate change” for the word “proof”.

    Thanks for the clarification!
    William

  5. 105
    pete best says:

    Re #100, nice one Dave. Its about time joe (average) got mad and started demanding the start of the new era in energy provision. Australia has a track record of love of coal and exports millions of tonnes of it each year. Get down the ports and blockade em (not very likely I know) and get them CSP power plants set up to provide your electricity on that baking rock which you do not want to be any hotter. Australia can lead the way and demand more than 5% emissions cuts, demand 55% for starters. Time to drive small(er) vehicles and hybrids to, design em and use solar and possibly wind as well.

    We all need this.

  6. 106
    Hank Roberts says:

    William, what do you think “answer a question” means in a science paper? Do you see something lacking in the cited paper that you think could or should be there, or that another later paper could add?
    Do you understand how the IPCC describes levels of confidence, and why?

  7. 107
    truth says:

    Hank Roberts: re [80]
    In defence of myself against your remarkable tirade—
    I have nothing whatever to do with those blogs or entities you list—I’m merely someone who wants to see both sides of this issue aired.
    Since the measures called for by the AGW proponents have the potential for enormous damage to economies and standards of living around the world, I would think it should be permissible to discuss all aspects of it, without being subjected to sneers and smear.
    What exactly is it in my posts that you find inconsistent with the reported findings of those scientists?
    I had not read the article in the link you provided, but taking that into account too, the statement that the Indian ocean is warmer than at any other time on record—-with the records being only a little more than 100years old, how much weight can be given to ‘unprecedented’ in the record of the preceding thousands of years.
    How can we know from such a short record, that the warming of the Indian Ocean is not part of a natural cycle?
    The quote you give—‘The current Indian Ocean warming is unprecedented, and probably related to climate change, researchers say’—is a quote from an environmental reporter—not a direct quote from the scientists—and in any case , it doesn’t mention anthropogenic climate change.
    Ike Solem did in fact liken the Indian Ocean Dipole conclusions to a ‘fossil fuel lobby response’ did he not—so why is it a red herring?

  8. 108
    gjp says:

    Re #102 Hank Roberts

    Page 5:
    “The lack of negative IOD events thus deprives Southeast Australia of its normal rainfall quota. In addition, it is apparent from Fig. 1c that drought conditions during the Big Dry have been exacerbated by higher temperatures (Nicholls, 2004),leading to the lowest PDSI value on record (Fig. 1d).”

  9. 109
    Hank Roberts says:

    > both sides

    Too simple. There’s far more than “two sides” to study here.

    > 100 years ….”unprecedented” … preceding thousands of years …

    Paleo records of ocean temperatures, not the 100-year thermometer record.

    > all aspects

    Good approach.

  10. 110
    Ray Ladbury says:

    The ironically named “truth” says, “I have nothing whatever to do with those blogs or entities you list—I’m merely someone who wants to see both sides of this issue aired.”

    So, what two sides would those be. I mean we’ve got the climate scientists–you know, the ones with all the evidence on their side. What’s the other side? Those who insist on having an opinion despite having no evidence to back it up?

    It is fine to debate policy–what we do about climate change. We are all affected by this question, and so we should all have a say in the decision. On the other hand, there is no question that the decision has to be based on the best science available–and that is the consensus model of Earth’s climate, of which anthropogenic causation of the current warming epoch is an inescapable conclusion.

  11. 111
    Nick Gotts says:

    “I have nothing whatever to do with those blogs or entities you list—I’m merely someone who wants to see both sides of this issue aired.” – “truth”

    Yeah, yeah. The scientific issues have been and are being fully aired in the peer-reviewed literature, and the overwhelming majority of relevant experts agree that anthropogenic climate change is real, and requires urgent action. There is plenty of room for public and political debate on what that action should be – but at this stage, arguing about whether anthropogenic climate change is real and requires a radical response, is just as irresponsible, obscurantist and dangerous as arguing that smoking is unrelated to cancer, or HIV to AIDS.

  12. 112

    truth wrote:

    “I’m merely someone who wants to see both sides of this issue aired.”

    It must be nice to have such an Olympian perspective.

    I’m merely someone who wants to see some effective action taken to preserve the civilization of which I am a part, in the face of the well-characterized and credible threat of AGW.

  13. 113
    Rod B says:

    I’ll bite my tongue…, let the pep rally continue…

  14. 114
    Pat N says:

    Re: 96, DJA said … “We really need to understand what influence fuel loading has on extreme fires. This is more important than relating this fire to climate change”.

    However in #87 dhogaza had already showed how … “climate change is interacting with our other efforts to totally screw up native ecosystems in an unpleasant way …”.

    Fires in the Boundary Waters in northern MN and Canada are no doubt related to climate change, link below.

    http://www.alumni.umn.edu/Lee_Frelich_discusses_the_Boundary_Waters.html

    Related:

    http://www.mnforsustain.org/climate_snowmelt_dewpoints_minnesota_neuman.htm

  15. 115
    Florifulgurator says:

    Re 107… (too funny that, I can’t resist…)

    Since the measures called for by the AGW proponents have the potential for enormous damage to economies

    Now who is doing “enormous damage to economies” nowadays?

  16. 116
    Jerry Toman says:

    Re: #97

    “I suggest you build one…”

    What is your offer for me to come there and oversee the selection of location, as well as the design and construction of the facility?

    In addition to a work visa, I’ll need about a $5 M budget, an agency sponsorship (e.g., University, State government), permits, etc.

    Of course, I would need support for this project from distinguished Australian engineers and climate scientists, as well.

    How many of you are willing to “go out on a limb” in support of this idea? Not many, I suppose, due to the “risk aversion” mentality that prevails just about everywhere, even in the face of the probability of catastrophic consequences which would accrue by doing nothing.

    I enjoy “modern art” as much as the next guy, o ye of little faith.

  17. 117
    William says:

    #111 Nick
    Although I empathize with the ferocity with which you hold your opinions, I take issue with your statement that “.. arguing about whether anthropogenic climate change is real and requires a radical response, is just as irresponsible as.. ”

    This blog “is a commentary site on climate science” and IMHO your statement seems unscientific. “Unlike a mathematical proof, a scientific theory is empirical, and is always open to falsification, if new evidence is presented. Even the most basic and fundamental theories may turn out to be imperfect if new observations are inconsistent with them.” (from the Wikipedia definition of Scientific method).

    If we are to believe your statement, then the “science” and study of our climate is over and there is no longer a purpose for a blog such as Real Climate to exist unless we agree to limit the discussion to how to implement policy based on a scientific certainty that we no longer have to study.

    I’m open to the possibility that there are new observations to include, new processes to understand, old processes to understand better and new ways to look at information that yield conclusions different than what I understand today. The imperfections found in theories today can be the basis for their replacement by new theories in the future.
    Thanks
    William

  18. 118
    Ray Ladbury says:

    Rod B. says “I’ll bite my tongue…, let the pep rally continue…”

    No, by all means, Rod, if you have something substantive to say about the science, contribute.

    No?

    Oh well.

  19. 119
    Joe Hunkins says:

    William thanks for the quotes from the Karoly Gov summary. His analysis there seems extremely well reasoned to me.

    David Karoly could you characterize the AGW causality link for the benefit of commenters here who (clearly and wrongly) want to assign “most” of the cause of these fires to AGW, which is unsupportable by any reasonable interpretation of the data.

    Hank you keep noting the shifting of the mean temperature picture as if it strongly suggests some sort of causality here. It does not. Although David is noting a possible small connection to AGW (reasonable assertion), several commenters seem to assign a high causal value to AGW, which is unsupported by anything referenced here and certainly not supported by Karoly’s (excellent) analysis of the situation for the Australian Government.

    Ray you seem to think the underbrush is more important than the trees. True underbrush often creates conditions for starting the ire but my understanding is that in Australia’s catastrophic case we’d consider the trees – a vastly larger source of fuel – more important in terms of how much damage was done.

    JCH you maintain that the source of ignition is NOT important, even in cases of arson? AGW > Arson as cause here really strains credulity unless your point is simply the obvious one – that overall dryness conditions matter. Still, it seems like others here you want AGW to top many lists of causal factors when in fact it AGW is generally at most a small contribution to other causal factors. Clearly that’s the case here if Karoly’s analysis is to be respected as it should be.

  20. 120
    Jim Galasyn says:

    Most southern hemisphere plant species face extinction

    MOST southern hemisphere plants – except for weeds – will not be able to adapt to rapid climate change, a study of more than 11,000 species suggests.

    Researchers, including the Sydney botanist Peter Weston, traced the history of plants that live in a range of different habitats including bogs, alpine regions, rainforests and arid environments.

  21. 121
    Doug Bostrom says:

    re 107 ironic “truth”: I think what you’re talking about is “teaching controversy”, not actually discussing interpretation of agreed facts. “Teaching controversy” is how “Intelligent Design” advocates operate in the face of overwhelming contrary evidence; they’ve learned that making noise can substitute for lack of facts. More on this topic here:
    http://www.re-discovery.org/

  22. 122
    William says:

    #41 dhogaza + #114 Pat N
    You stated earlier:
    “Cheatgrass (from the eastern European steppes). US. Sigh. Though it wasn’t brought in to improve grazing (rather, to “cheat” seed and grain shipments). But it has altered the fire ecology of much of the Western US immensely. More frequent, earlier, hotter burns than anything on the prairie co-evolved with.”

    So it’s possible that an invasive species explains fire ecology in the Western USA rather than climate change? We can say for certain that converting tens of millions of acres of Midwestern prairie into cropland eliminated the 5-10 year cycle of prairie fires. Can anyone comment on what that change in habitat may have had on climate?

  23. 123
    Ian George says:

    The conditions prior to these fires were basically the same as 1939. There was a blocking pressure system in the Tasman Sea and a strong monsoonal system in the north (Cairns had over 600mm that January). This causes higher than normal temps as heat is pushed from Qld down to the south-east (this also happened in the March heatwave last year). Add a cool front beginning to push through and you have a strengthening of winds which exacerbated the problem. In 1851, close to 25% of Vic was burnt out (5m hectares), well before AGW.

  24. 124
    Nick Gotts says:

    “So it’s possible that an invasive species explains fire ecology in the Western USA rather than climate change?” – William

    Another fine instance of the inability to understand the possibility of multiple causation.

  25. 125
    Hank Roberts says:

    > rather than climate change?

    It’s not that simple, William. Multiple factors, different levels of confidence attributable to them.

    Don’t make the mistake of thinking there is “an AGW theory” and going down the “therefore it can always be falsified” trail. Nobody here wants to retype the huge amount of discussion already put into that. You can look it up. Spencer Weart’s book (first link under Science) should clear that confusion up.

  26. 126
    duBois says:

    well before AGW.

    AGW isn’t going to cause some new kind of weather to be created.

  27. 127
    david says:

    The first of a couple of response…

    Here is the time series of annual FFDI for central Victoria http://farm4.static.flickr.com/3614/3290577179_3779ac75f0.jpg?v=0 . There are issues with early wind data etc. The recent increase is due to a combination of the most severe drought on record and the highest temperatures on record. Also note that the 2008/09 numbers still have 5 months to go. The trend is pretty obvious – and this is not likely to be affected by an UHI effects.

  28. 128
    Pat N says:

    Re: #122

    Earlier spring thaws should not be ignored in efforts to understand fire ecology in the Western USA and Upper Midwest. See link to Westerling, A. L., et al., 2006 and my link in #114).

  29. 129
    MarcH says:

    Land clearing in SE Australia since the 1800s can explain the low humidity, increased wind speed and extreme temperatures that helped make these bushfires so intense…why no mention of this David? Why the narrow focus on CO2?

    From the ABC opinion page
    Land clearing helps explain heatwave
    Fri Feb 13, 2009 12:22pm AEDT

    Global warming activists have been quick to blame the extreme weather conditions that helped turn Victoria’s bushfires into a fire storm solely on increased levels of carbon dioxide.

    This simplistic argument has been shown to be false by research at the University of Queensland led by Dr Clive McAlpine, that demonstrates that 150 years of land clearing has added to the warming and drying of eastern Australia leading to increases in temperature and decreasing humidity. Australian native vegetation holds more moisture than broadacre crops and improved pastures, and this moisture evaporates and recycles back as rainfall and also raises humidity.

    It also reflects less shortwave solar radiation into space, and this process keeps the surface temperature cooler and aids cloud formation. As high pressure systems slowly pass the southern part of the continent over summer the air they draw down from the north, over cleared land, has been getting hotter and dryer and helps explain this summer’s heat wave that probably made these bushfires more intense than those of Black Friday in 1939 and Ash Wednesday in 1983.

    Land clearing can explain the low humidity, increased wind speed and extreme temperatures…why no mention of this David?

    Reducing the chances of future extreme weather events then does not solely depend on reducing CO2 emissions but in restoring vegetation to critical parts of New South Wales and Queensland. Use of CO2 as a scapegoat for extreme weather events has blinded us from looking for the real influences on regional climate systems.

    Any comments David?
    McAlpine’s modelled temperature changes based on land use changes account for virtually all warming in SE Australia since 1950 leaving little room for CO2…have we over played the role of CO2?

    McAlpine’s paper available via
    http://www.omc.uq.edu.au/news/documents/ModellingImpactsVegetationCover.pdf

    [Response: David can answer for himself, but, really, what kind of strawman argument are you putting forward here? ‘CO2′ is not even mentioned above, let alone ‘solely’ blamed for everything. This knee-jerk transformation of any statement that says climate change is possibly a factor in X, to the accusation that environmentalists claim that X is definitely and exclusively caused by increases in CO2, is as sophmoric as it is predictable. If you want a serious discussion about the potential for land use change to impact climate, then by all means let’s discuss it (though frankly it is still anthropogenic climate change). But starting off from the premise that it must be anything (anything!) except CO2 is just stupid. – gavin]

  30. 130
    William says:

    #125 Hank
    You stated “Don’t make the mistake of thinking there is an AGW theory”. I think you may have mis-spoken, AGW is a theory and one that may turn out to be falsified. I’m open to the possibility and enjoy participating in these blogs in order to keep up with the science. I’ve seen comments that refer to me as a denialist which is confusing. I would not deny that humans have impacted the environment and climate of this planet. We may only disagree as a matter of “degree” as to the how and how much or whether a particular study makes conclusions that can and should be questioned.

    Nick #124
    I understand multiple causality just fine. I don’t understand how it seems to be ignored whenever the word climate gets mentioned. I’m open to hear a reasoned discussion of the multiple causalities involving forest fires in the Western USA if you wish to start there.
    Thanks for the discussion!

    [Response: Calling anthropogenic climate change a “theory” is at best a stretch, and at worst just wrong. There are elements of it that are indeed theoretical in nature. For example, that greenhouse gases have a warming influence on the atmosphere might be called a theory, one that in fact has stood up quite well to scrutiny. That we are increasing greenhouse gas concentrations through fossil fuel burning is not a ‘theory’, its an observation. That this should have a warming influence on the planet is thus a combination of the theory of how greenhouse gases warm the atmosphere, with the observation that we are increasing greenhouse gas concentrations. “AGW” therefore combines attributes which are indeed ‘theoretical’ in nature, and others which are merely phenomenological. As such, it is not a ‘theory’ in the standard sense of the term. For an analogy, there is a ‘theory of gravity’ but there is not a ‘theory-of-gravity-making-apples-fall’. -mike]

    William

  31. 131
    Rod B says:

    Ray, right. I bit my tongue because I didn’t have anything substantive to say about the science. ;-) Thanks for the encouragement.

  32. 132
    David Horton says:

    Several mentions here of “fuel load”, the smokescreen of choice of denialists down to and including the very oxymoronically named Ms Devine. Fuel loads become higher in drought because of a lack of decay which would normally break down what in a garden we would call mulch and feed the nutrients into the soil. This cycle is a vital part of maintaining forest ecosystems, and adding extensive prescribed burning to a forest already under stress from drought is going to cause irreversible damage to these ecosystems. Damage that will ironically cause them to become even more fire prone (http://www.blognow.com.au/mrpickwick/84979/Fire_and_Australian_Society.html and http://www.blognow.com.au/mrpickwick/36297/Will_prescribed_burning_prevent_bushfires.html). People pushing this “reduce fuel load” line have a political agenda which is not in the interests of the people of Victoria. Which wants to maintain the denial of climate change as long as possible, and exploit the forests.

  33. 133
    Lynn Vincentnathan says:

    Here’s an idea re clearing out dried plant life that could be fuel in a dangerous wildfire. How about clearing it & turning it into cellulosic biofuel. Controlled burning of it may not only be dangerous, but also would add GHGs to the atmosphere.

    Here’s something about recent break-through in cellulosic biofuel: http://features.csmonitor.com/environment/2009/02/13/the-%E2%80%98holy-grail%E2%80%99-of-biofuels-now-in-sight/

    I know Hank says we can’t run the entire world on (non-harmful) biofuels, but every little bit helps, including just driving less.

    And there is the issue of the nutrients needed for the soil, and I still haven’t heard one way or the other, whether the remainder of cellulosic biofuels might be a good soil amendment, tho the article addresses the issue of needing to leave plants there for the soil, depending on how much the soil might be depleted or healthy already.

  34. 134
    Jim Bouldin says:

    #122: “So it’s possible that an invasive species explains fire ecology in the Western USA rather than climate change? We can say for certain that converting tens of millions of acres of Midwestern prairie into cropland eliminated the 5-10 year cycle of prairie fires. Can anyone comment on what that change in habitat may have had on climate?”

    No, it’s ONE contributing factor among many, not an “either/or” issue, and is so only in those areas where cheatgrass is common–generally the more arid parts of the west. Large forested areas are unaffected. As to mid-western croplands, the changes you mention also contributed to large reductions in soil carbon, which are much lower on intensive ag lands than prairies. Further, a good chunk of the mid-west was converted from forest to ag, not prairie to ag, with huge carbon losses. As to your question, yes, there is a good body of literature on the effects of land use change on local/regional climate. Gordon Bonan at NCAR has published extensively on the topic.

  35. 135
    dhogaza says:

    I understand multiple causality just fine. I don’t understand how it seems to be ignored whenever the word climate gets mentioned. I’m open to hear a reasoned discussion of the multiple causalities involving forest fires in the Western USA if you wish to start there.

    Which is why you quote mined the part of my comment which mentioned cheatgrass alone, leaving out my comments on how climate change is interacting with the ecology of this invasive species to further change the timing and frequency of western USA rangelands.

    The whole point of my comment was about multiple causality.

    Quote mining is a sin.

  36. 136
    jt says:

    an informed comment on fuel loads

    http://www.smh.com.au/opinion/fire-risk-will-never-be-eliminated-20090217-8a99.html

    “Research indicates that the relative effect of weather on fire behaviour is magnified under conditions of very high and extreme fire danger (above a rating of 25). Fires in extreme conditions (above a rating of 50) can develop their own weather, including winds of tornado strength. Weather becomes the dominant process governing the rapidity of spread and intensity. This can lead to a considerable underestimation of the intensity of fire produced by a particular amount of fuel.”

    “The theory of risk mitigation by fuel treatment is based on definitions of “safe” or “controllable” levels of fuel derived from this limited knowledge base. Formal, operational models that allow us to accurately predict what will happen at a fire danger rating of 50, let alone 150, do not exist.”

    “On a scale of zero to 10, where 10 equates to the level of risk achieved by doing nothing and zero equates to concrete, our efforts result in a ranking of 9½. If we were to double our effort, the rating might be reduced to nine. Doubling our effort would require doubling expenditure. Halving risk to a rating of five or less would require an increase of an order of magnitude or more in treatment, at a commensurate cost. Our ability to maintain such a level of spending in the long-term is questionable.”

    “This overview reflects the nature of our environments: the rate at which vegetation grows and the occurrence of severe weather. Occasional, major fires are a longstanding part of our ecological furniture, with their imprint hard-wired into the lifecycles of our biota. If we are to live in these environments we must do so on the understanding that we will not eliminate risk.”

  37. 137
    John Mashey says:

    re: Cheatgrass, invasive species, bad trees

    I recommend a nice presentation, with many good maps and graphs by U of Toronto researchers Rowan Sage and Heather Coiner Global Change and Invasive Plants in Canada, of which half is about the Northward progress of kudzu towards Canada, and the rest about bioinvasives in general, including cheatgrass.

    Conclusion: kudzu could survive in Canada in less than 20 years.

    [Of course, it’s already in NorthEast Australia too, since it got brought there, just as it was brought to the US South.]

    Kudzu is one of those things, like:
    – the beetles that are expected to kill every lodgepole pine in Colorado, and are right now chewing their way through British Columbia and into Alberta.
    – mosquitoes

    Whose Northward range stops where there are coldspells of specific durations of low temperatures. Having warmer nights and winters, and less deep or less frequent coldspells [classic AGW signature], lets them expand poleward. Nobody wants more [kudzu, pine beetles, mosquitoes], even if they might like warmer weather. Kudzu has the added impetus (along with poison ivy) of responding especially well to rising CO2.

    =====
    People argue endlessly about the effects of AGW on relatively low-frequency events, i.e., where the effect is to shift a distribution, and it is not always easy to extract signal from noise convincingly enough for people unused to thinking in distributions.

    On the other hand, the biological evidence, like showing widespread range extensions poleward for things *no one* wants there is very hard to wish away, although people try. Likewise, the movement of the equator-side boundary of desired crops poleward is hard to ignore if, for example, you have a vineyard or sugar maple trees. Canada may be happy at the poleward extension of those two zones; California and Vermont aren’t.

    In particular, such evidence clearly has little or nothing to do with UHI, statistics of interpolation, uncertainty levels, skill of models, exact measurements of hurricane strength, frequency and intensity of (relatively) rare events like the worst hurricanes and worst forest fires.

    If we knew *nothing* else, if there were no GISS or Hadley or satellites, to know it’s warming, it should be enough to know that plants and animals are mostly moving uphill and poleward, when they can, with flying species like birds and insects in the lead, and slow ones like trees behind.

    See IPCC AR4 WG II, Chapter 1, starting with Tables 1.8 and 1.9, or current thread at Brave New Climate.

    [Wish for RC: maybe a (guest?) post on this topic, with a few good maps,

    ===
    My sympathy for SW Australia, a place where I’ve enjoyed many trips….
    However, returning to invasive species, I’d gladly give Oz some California redwoods [relatively fire-resistant, maybe growable around Canberra?] if we could also send back all the eucalyptus that now grow here in CA. That is one nasty kind of tree.

  38. 138
    Jim Bouldin says:

    #132: David, the issue is more complex than that. I don’t know what Victorians “are saying” about fuel loads, but fire reduction, drought, productivity, and fire regime are related in a number of different ways. Generally, increased fuel loads in fire-prone areas ARE a serious issue, contributing to changes in fire regimes and effects. By no means does that mean that climate change is not important also. It’s effects are just made worse by the increased fuel available to burn.

  39. 139
    MarcH says:

    Gavin says “If you want a serious discussion about the potential for land use change to impact climate, then by all means let’s discuss it (though frankly it is still anthropogenic climate change).”

    Attribution of the numerous factors that affected this summer’s heat wave in SE Australia that contributed to the extreme fire conditions is of great import from a policy perspective. A reduction in CO2 output may reduce the potential for future extreme weather events, however if done in the absence of addressing land use changes and probably more importantly undertaking systematic fuel reduction burns around settled areas it will not do a great deal.

    In regard to actually doing something practical, restoring areas of native vegetation in parts of NSW and QLD is much more achieveable over the next 2 decades than keeping atmospheric CO2 below 450 ppm.

    Any comment DK?

  40. 140
    David B. Benson says:

    Lynn Vincentnathan (133) — If biomass, any biomass, can be collected for anaerobic digestion, the output of the digester consists of:

    (1) solids for soil amendments;

    (2) pure water, purer than almost all natural sources;

    (3) biogasse, about 65–70% CH4 with the rest almost all CO2.

    The biogasse can be burned to generate electricity or separated into biomethane (of high enough quality to introduce into natural gas pipelines or used in CNG vehicles) and the acid gas component, almost pure CO2. If the sulfer is scrubbed from the acid gas, the result is a (mostly) CO2 product with industrial uses. Or else figure out a way to sequester it.

    There is nothing new in any of the above. The usual problem is the high cost of centralizing the biomass.

  41. 141
    Chris Colose says:

    As a follow up to Dr. Mann’s insightful comment to #130, “AGW” is a unifying concept that emerges as a consequence of the multiple physical aspects of the climate system and the perturbations that cause it to change.

    In this sense AGW follows from the physics of radiative transfer, fluid dynamics, the physics of evapotranspiration and albedo impacts that comes with land use, etc. Not only do such physics manifest themselves into what we call “AGW,” but it depends also on the trajectories of what we actually do (how much deforestation or CO2 do we decide to emit). AGW is not an organizing principle of climate in the sense that gravitational force is proportional to the product of two objects mass divided by the square of their distances. I’m not sure if there’s any significant meaning to “AGW theory” as there is “theory of gravity” in the sense that the former doesn’t intrinsically make predictions or have a fundamental explanatory focus.

    Rather, the predictive power for what to expect as CO2 concentrations increase over time comes from the paleoclimate record, theoretical expectations, modeling effort or some combination of these (which are in themselves fundamentally rooted in climate behavior). AGW is just what we call all this bundle of theories and observations for convenience.

    When we see the globe warming as a consequence of the physical laws (or “theories”) that’s what we call global warming (duh) and the “A” is simply a qualifer that attribution has been done. “Falsifying AGW theory” sounds something like “falsifying the theory of summer and winter.” These things are just names and observations; the physical significance (and what can be modified) is the causes, or the combinations of these causes and how they behave in time.

  42. 142
    Jim Bouldin says:

    #139:

    Both local and global mitigation efforts are needed, as the effectiveness of local solutions will be constrained, in many cases, by the effectiveness of mitigation at the larger scale. And restoring land cover to forested vegetation is not necessarily either easy or quick. I fully agree that efforts need to be made at the local scale though.

    #136:

    Paragraph starting “On a scale of zero to 10,…”: lot of questionable generalizations and numbers there. And although precise knowledge of the relationship between fuel structure and extreme weather may be lacking, there is often good knowledge of historical fire regimes and/or events in relation to either climate or specific weather events, to provide guidance.

  43. 143
    Craig Allen says:

    Marc H 129:

    It makes sense that land clearing will have altered s-e Australian climates to some degree. I’d love to see some research that quantifies this.

    However, the Cape Otway and Wilson’s Promontory lighthouse meteorological station temperature datasets show warming that is in broadly line with stations in inland Victoria. These stations receive most of their weather from over the ocean to the south west, so the rising temperatures that they exhibit are unlikely to be due to land clearance alone.

    (Of course, to nail this down more definitively, it would be necessary to separate out the data from days with north and north-east prevailing winds. If all days with prevailing winds from the south showed no warming and visa versa, then it would suggest that all the warming is due to something happening over the land rather than a more general phenomonon.)

  44. 144
    Ray Ladbury says:

    William, The theory is of Earth’s climate. CO2, as a well mixed, long-lived greenhouse gas plays an important role in that theory. That humans are warming the planet by increasing the amount of CO2 in the atmosphere is an inescapable consequence of the theory–as well as an observed fact.

    Rod, Snark when you don’t have anything to back it up with begets snark. We are here to learn or we are wasting our time.

  45. 145
    Ray Ladbury says:

    Joe Hunkins, Underbrush can serve as kindling. So can litter from the trees. If it’s dry enough, it’ll burn. I grew up in Colorado. In the summer time, about August, you didn’t dare have a campfire sometimes for fear of the whole forest going up in flames. The point is the fire doesn’t usually start in the trees unless there’s a lightning strike. Even then it’s usually understory or litter that gets it going. Once it’s going, though, it doesn’t matter. The flames will jump crown to crown

  46. 146
    Steve says:

    One of the biggest reasons for the loss of life in this disaster has nothing to do with climate change. It was illegal for homeowners to fell trees around their homes to create a fire break. Creating such an area could have saved many hundreds of lives. A fellow Kiwi and her Ozzy husband did, illegally, create this fire break and their house and the lives of their family were saved. It was the insane policies of the Victorian government that allowed this disaster to occur. One which they quickly chose to ignore after the tragedy when they instructed families to create such a fire break.

    Fires have always occurred in Australia and ascribing this specific fire to climate change seems tenuous at best. Especially since it was common practice among aborigines before white settlers arrived to create controlled fires to reduce the chances of these kinds of larger fires occurring.

  47. 147
    Nick says:

    John Mashey @#137,love your work, but please don’t send any more Californian pines to Australia: plantations of mature Pinus radiata (known in Aus. as Monterey Pine) on Canberra’s western margins, helped deliver the flames into a number of suburbs.

    Earth Observatory has posted satellite imagery of the Murrindindi-Kinglake fires which shows the damage caused by the windshift from NW to SSW driving the fire up out of the forested southern gullies northward onto Kinglake’s semi-rural plateau. A critical windshift.

  48. 148
    JCH says:

    JCH you maintain that the source of ignition is NOT important, even in cases of arson? AGW > Arson as cause here really strains credulity unless your point is simply the obvious one – that overall dryness conditions matter.

    The arsonists could not cause the near-perfect conditions that allowed the disastrous fires in SE Australia to happen. Since the conditions that allowed for the fires to happen are indifferent to the source of ignition, the causes of the conditions trump the cause of the ignition. AGW is in the list of potential causes of the conditions.

    I suppose Chicago’s Lomborgs could have argued for rebuilding their city just as it was before the fire as the cow did it.

  49. 149

    “truth” writes:

    Since the measures called for by the AGW proponents have the potential for enormous damage to economies and standards of living around the world,

    Who says? You?

    I think conservation and switching to renewable sources of energy will help the economy, not hurt it. And I think doing nothing about global warming will hurt the economy far more than any mitigation effort possibly could.

  50. 150
    PHE says:

    Lynn V (133) – collecting up the leaf litter and turning into biofuel. That’s a good idea, rake the ground clear. I’m sure the benefits will outweigh the impact on the natural woodland habitat and its species. Now of course, we have to be careful how to collect it. We can’t use mechanical rakers, vaccum cleaners or trucks, as the added CO2 emissions would surely outweigh the benefit in this case. Using horse power could cause the same methane prblem as cows. We’d have to rake it up by hand. Is 21 million Australians enough to manage this? They’ll need to ramp up the birth rate. But then..


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