Summary Points
1) Global wildfire activity has decreased in recent decades, making any localized increase (or decrease) in wildfire activity difficult to attribute to ‘global climate change’.
2) Like California, Australia is prone to bushfires every year during the dry season. Ample fuel and dry weather exists for devastating fires each year, even without excessive heat or drought, as illustrated by the record number of hectares burned (over 100 million) during 1974-75 when above-average precipitation and below-average temperatures existed.
3) Australian average temperatures in 2019 were well above what global warming theory can explain, illustrating the importance of natural year-to-year variability in weather patterns (e.g. drought and excessively high temperatures).
4) Australia precipitation was at a record low in 2019, but climate models predict no long-term trend in Australia precipitation, while the observed trend has been upward, not downward. This again highlights the importance of natural climate variability to fire weather conditions, as opposed to human-induced climate change.
5) While reductions in prescribed burning have probably contributed to the irregular increase in the number of years with large bush fires, a five-fold increase in population in the last 100 years has greatly increased potential ignition sources, both accidental and purposeful.
Historical Background
Australia has a long history of bush fires, with the Aborigines doing prescribed burns centuries (if not millennia) before European settlement. A good summary of the history of bushfires and their management was written by the CSIRO Division of Forestry twenty-five years ago, entitled Bushfires – An Integral Part of Australia’s Environment.
The current claim by many that human-caused climate change has made Australian bushfires worse is difficult to support, for a number of reasons. Bushfires (like wildfires elsewhere in the world) are a natural occurrence wherever there is strong seasonality in precipitation, with vegetation growing during the wet season and then becoming fuel for fire during the dry season.
All other factors being equal, wildfires (once ignited) will be made worse by higher temperatures, lower humidity, and stronger winds. But with the exception of dry lightning, the natural sources of fire ignition are pretty limited. High temperature and low humidity alone do not cause dead vegetation to spontaneously ignite.
As the human population increases, the potential ignition sources have increased rapidly. The population of Australia has increased five-fold in the last 100 years (from 5 million to 25 million). Discarded cigarettes and matches, vehicle catalytic converters, sparks from electrical equipment and transmission lines, campfires, prescribed burns going out of control, and arson are some of the more obvious source of human-caused ignition, and these can all be expected to increase with population.
Trends in Bushfire Activity
The following plot shows the major Australia bushfires over the same period of time (100 years) as the five-fold increase in the population of Australia. The data come from Wikipedia’s Bushfires in Australia.
As can be seen, by far the largest area burned occurred during 1974-75, at over 100 million hectares (close to 15% of the total area of Australia). Curiously, though, according to Australia Bureau of Meteorology (BOM) data, the 1974-75 bushfires occurred during a year with above-average precipitation and below-average temperature. This is opposite to the narrative that major bushfires are a feature of just excessively hot and dry years.
Every dry season in Australia experiences excessive heat and low humidity.
Australia High Temperature Trends
The following plot (in red) shows the yearly average variations in daily high temperature for Australia, compared to the 40-year average during 1920-1959.
Also shown in Fig. 2 (in blue) is the average of 41 CMIP5 climate models daily high temperature for Australia (from the KNMI Climate Explorer website). There are a few important points to be made from this plot.
First, if we correlate the yearly temperatures in Fig. 2 with the bushfire land area burned in Fig. 1, there is essentially no correlation (-0.11), primarily because of the huge 1974-75 event. If that year is removed from the data, there is a weak positive correlation (+0.19, barely significant at the 2-sigma level). But having statistics depend so much on single events (in this case, their removal from the dataset) is precisely one of the reasons why we should not use the current (2019-2020) wildfire events as an indicator of long-term climate change.
Secondly, while it is well known that the CMIP5 models are producing too much warming in the tropics compared to observations, in Australia just the opposite is happening: the BOM temperatures are showing more rapid warming than the average of the climate models produces. This could be a spurious result of changes in Australian thermometer measurement technology and data processing as has been claimed by Jennifer Marohasy.
Or, maybe the discrepancy is from natural climate variability. Who knows?
Finally, note the huge amount of year-to-year temperature variability in Fig. 2. Clearly, 2019 was exceptionally warm, but a good part of that warmth was likely due to natural variations in the tropics and subtropics, due to persistent El Nino conditions and associated changes in where precipitation regions versus clear air regions tend to get established in the tropics and subtropics.
Australia Precipitation Trends
To drive home the point that any given year should not be used as evidence of a long-term trend, Australia precipitation provides an excellent example. The following plot is like the temperature plot above (Fig. 2), but now for precipitation as reported by the BOM (data here).
We can see that 2019 was definitely a dry year in Australia, right? Possibly a record-setter. But the long-term trend has been upward (not downward), again illustrating the fact that any given year might not have anything to do with the long-term trend, let alone human-induced climate change.
And regarding the latter, the blue curve in Fig. 3 shows that the expectation of global warming theory as embodied by the average of 41 climate models is that there should have been no long-term trend in Australia precipitation, despite claims by the media, pseudo-experts, and Hollywood celebrities to the contrary.
It should be kept in mind that wildfire risk can actually increase with more precipitation during the growing season preceding fire season. More precipitation produces more fuel. In fact, there is a positive correlation between the precipitation data in Fig. 3 and bushfire hectares burned (+0.30, significant at the 3-sigma level). Now, I am not claiming that hot, dry conditions do not favor more bushfire activity. They indeed do (during fire season), everything else being the same. But the current 2019-2020 increase in bushfires would be difficult to tie to global warming theory based upon the evidence in the above three plots.
Global Wildfire Activity
If human-caused climate change (or even natural climate change) was causing wildfire activity to increase, it should show up much better in global statistics than in any specific region, like Australia. Of course any specific region can have an upward (or downward) trend in wildfire activity, simply because of the natural, chaotic variations in weather and climate.
But, contrary to popular perception, a global survey of wildfire activity has found that recent decades have actually experienced less fire activity (Doerr & Santin, 2016), not more. This means there are more areas experiencing a decrease in wildfire activity than there are areas experiencing more wildfires.
Why isn’t this decrease being attributed to human-caused climate change?
Concluding Comments
There are multiple reasons why people have the impression that wildfires are getting worse and human-caused climate change is to blame. First, the news tends to report only disasters… not a lack of disasters. The desire for more clicks means that headlines are increasingly sensationalized. The media can always find at least one expert to support the desired narrative.
Second, the spread of news is now rapid and it penetrates deeply, being spread through social media.
Third, an increasing number of environmental advocacy groups seize upon any natural disaster and declare it to be caused by increasing CO2 in the atmosphere. The hyperbolic and counter-factual claims of Extinction Rebellion is one of the best recent examples of this.
This is all against a backdrop of government funded science that receives funding in direct proportion to the threat to life and property that the researcher can claim exists if science answers are not found, and policy is not changed. So, it should come at no surprise that there is political influence on what research gets funding when the outcome of that research directly affects public policy.
My personal opinion, based upon the available evidence, is that any long-term increase in wildfire activity in any specific location like Australia (or California) is dominated by the increase in human-caused ignition events, whether they be accidental or purposeful. A related reason is the increasing pressure by the public to reduce prescribed burns, clearing of dead vegetation, and cutting of fire breaks, which the public believes to have short term benefits to beauty and wildlife preservation, but results in long term consequences that are just the opposite and much worse.
Recent news reports claim that dozens of people have been arrested in Australia on arson charges, a phenomenon which we must assume has also increased by at least five-fold (like population) in the last 100 years. Accidental sources of ignition also increase in lockstep with the increasing population and all of the infrastructure that comes along with more people (vehicles, power lines, campfires, discarded matches and cigarettes, etc.)
So, to automatically blame the Australian bushfires on human-caused climate change is mostly alarmist nonsense, with virtually no basis in fact.
Duane Schlottke says
The over 180 ‘arrested’ Arsonists are the cause of these great fires
Poor Richard says
Of all the variables (temperature, precipitation, wind, etc.) involved in bush fires, only one can easily and effectively be controlled by humans: the availability of fuel lying around. Controlled burns work. The Aborigines used “cool burns” for millenia to reduce the frequency and severity of bush fires in Australia. The flames are only 2-4 feet high, not very intense, and move at a leisurely pace in the absence of wind. Animals can easily flee. The soil moisture and humus layer is largely unaffected. Plants requiring fire for their seeds to germinate are satisfied. Dry detritus on the ground is burnt up to the tune of roughly 90 percent, automatically diminishing the intensity of any future fires. And the result is a healthier, more vibrant environment for all.
Yet this approach has been largely ignored or only sporadically applied in the past decades in Australia, so that a tinderbox was created in heavily populated areas. Just like in California and other dry places with fire problems, it is the residents’ own fault that an avoidable crisis occurred. Be good stewards and your environment will thrive. Ignore your back yard and it will eventually go up in flames. Too bad the animals have to pay for human stupidity.
And the other factor which has been largely avoided by the press worldwide is premeditated arson. Bush fires in Australia are the result of careless or destructive people in roughly 13 percent of all fires. A further 37 percent of fires are listed as highly suspicious. Add that to the continent with the highest natural level of fire hazard and you have a very explosive mix. Not to mention that the population of Australia is five times what it was 100 years ago. More people in higher densities, who live on the coastal strips (85 percent of Australians live near the ocean), means you will obviously have more property damage and loss of life than in 1900. Just like property damage due to hurricanes in developed countries who have built up their beach areas, like the Gulf and Atlantic coasts of the US.
Burn smaller areas very frequently with low intensity and the problem goes away. Or you can just blame everything on climate change, so you do not have to learn real science in the first place. Put all that carbon dioxide in the air and watch the carbon-starved earth green … just like we have observed since the first satellites were put into orbit in the late 1950s. A greening earth will lead to less desertification, more precipitation, etc. Sorry Greta. The only mass extinction we are seeing is the extinction of rational thought, scientific literacy, ethical political behavior, critical thinking skills, and overall intelligence in the leftist-based propaganda machine called climate change “science”. But the fanatical cohorts of pseudo-science will never listen, so don’t waste your time talking sense to them. You are only casting your pearls before swine and wasting valuable beer-drinking time. Oh, wait. Beer has CO2 in it. That will be the next thing they ban after taking care of all the farting cows on the planet.
Paul McFadyen says
Bushfires are normal in Australia’s Eucalyptus forests. Over thousands of years Eucalypts have evolved to cope with bushfires. Eucalypts have lignotubers which shoot from the base after a fire. Many Acacia’s need fire to germinate.
Bushfires have long been part of Australian country folklore eg the 1905 poem “The Bushfire” by the iconic Australian poet Henry Lawson, http://www.ironbarkresources.com/henrylawson/BushFire.html
Herb White says
Thank you for your fine efforts. To me, this biggy issue begs yet another of many questions as to the connection of a particular scare tactic or ‘activist’ movement – LGBT as one more ownership of mass emotion overruling evidence, men competing in women’s sports via their deceived feelings (brainwashing of government policy makers trumps science), redefining marriage vs human history and science, word re- definitions to achieve a goal (i.e hate speech, bigot, intolerant), accusing the other party of exactly what you are doing and getting away with it via emotionally driven public ignorance, just for starters. These are all by clever design for the world controllers to finally achieve their one world government basically launched in the late l890’s by the Rothchild banking empire. Together, they are hugely effective in incrementally bringing down the USA, the last barrier standing in their way. Also, it would be interesting in hearing the Weather Channel ‘experts’ try to counter your science, but they wouldn’t dare risk such exposure, say what. Is this nationally dominating propaganda machine on your mailing list? Bless your ongoing impact.