The link below is to yet another article dealing with bushfires and the denial of climate change.
As the east coast bushfire crisis unfolds, New South Wales Premier Gladys Berejiklian and Rural Fire Service operational officer Brett Taylor have each warned residents bushfires can create their own weather systems.
This is not just a figure of speech or a general warning about the unpredictability of intense fires. Bushfires genuinely can create their own weather systems: a phenomenon known variously as firestorms, pyroclouds or, in meteorology-speak, pyrocumulonimbus.
The occurrence of firestorms is increasing in Australia; there have been more than 50 in the period 2001-18. During a six-week period earlier this year, 18 confirmed pyrocumulonimbus formed, mainly over the Victorian High Country.
Its not clear whether the current bushfires will spawn any firestorms. But with the frequency of extreme fires set to increase due to hotter and drier conditions, it’s worth taking a closer look at how firestorms happen, and what effects they produce.
What is a firestorm?
The term “firestorm” is a contraction of “fire thunderstorm”. In simple terms, they are thunderstorms generated by the heat from a bushfire.
In stark contrast to typical bushfires, which are relatively easy to predict and are driven by the prevailing wind, firestorms tend to form above unusually large and intense fires.
If a fire encompasses a large enough area (called “deep flaming”), the upward movement of hot air can cause the fire to interact with the atmosphere above it, potentially forming a pyrocloud. This consists of smoke and ash in the smoke plume, and water vapour in the cloud above.
If the conditions are not too severe, the fire may produce a cloud called a pyrocumulus, which is simply a cloud that forms over the fire. These are typically benign and do not affect conditions on the ground.
But if the fire is particularly large or intense, or if the atmosphere above it is unstable, this process can give birth to a pyrocumulonimbus – and that is an entirely more malevolent beast.
What effects do firestorms produce?
A pyrocumulonibus cloud is much like a normal thunderstorm that forms on a hot summer’s day. The crucial difference here is that this upward movement is caused by the heat from the fire, rather than simply heat radiating from the ground.
Conventional thunderclouds and pyrocumulonimbus share similar characteristics. Both form an anvil-shaped cloud that extends high into the troposphere (the lower 10-15km of the atmosphere) and may even reach into the stratosphere beyond.
The weather underneath these clouds can be fierce. As the cloud forms, the circulating air creates strong winds with dangerous, erratic “downbursts” – vertical blasts of air that hit the ground and scatter in all directions.
In the case of a pyrocumulonimbus, these downbursts have the added effect of bringing dry air down to the surface beneath the fire. The swirling winds can also carry embers over huge distances. Ember attack has been identified as the main cause of property loss in bushfires, and the unpredictable downbursts make it impossible to determine which direction the wind will blow across the ground. The wind direction may suddenly change, catching people off guard.
Firestorms also produce dry lightning, potentially sparking new fires, which may then merge or coalesce into a larger flaming zone.
In rare cases, a firestorm can even morph into a “fire tornado”. This is formed from the rotating winds in the convective column of a pyrocumulonimbus. They are attached to the firestorm and can therefore lift off the ground.
This happened during the infamous January 2003 Canberra bushfires, when a pyrotornado tore a path near Mount Arawang in the suburb of Kambah.
Understandably, firestorms are the most dangerous and unpredictable manifestations of a bushfire, and are impossible to suppress or control. As such, it is vital to evacuate these areas early, to avoid sending fire personnel into extremely dangerous areas.
The challenge is to identify the triggers that cause fires to develop into firestorms. Our research at UNSW, in collaboration with fire agencies, has made considerable progress in identifying these factors. They include “eruptive fire behaviour”, where instead of a steady rate of fire spread, once a fire interacts with a slope, the plume may attach to the ground and rapidly accelerate up the hill.
Another process, called “vorticity-driven lateral spread”, has also been recognised as a good indicator of potential fire blow-up. This occurs when a fire spreads laterally along a ridge line instead of following the direction of the wind.
Although further refinement is still needed, this kind of knowledge could greatly improve decision-making processes on when and where to deploy on-ground fire crews, and when to evacuate before the situation turns deadly.
Last week saw an unprecedented outbreak of large, intense fires stretching from the mid-north coast of New South Wales into central Queensland.
The most tragic losses are concentrated in northern NSW, where 970,000 hectares have been burned, three people have died, and at least 150 homes have been destroyed.
A catastrophic fire warning for Tuesday has been issued for the Greater Sydney, Greater Hunter, Shoalhaven and Illawarra areas. It is the first time Sydney has received a catastrophic rating since the rating system was developed in 2009.
No relief is in sight from this extremely hot, dry and windy weather, and the extraordinary magnitude of these fires is likely to increase in the coming week. Alarmingly, as Australians increasingly seek a sea-change or tree-change, more people are living in the path of these destructive fires.
Unprecedented state of emergency
Large fires have happened before in northern NSW and southern Queensland during spring and early summer (for example in 1994, 1997, 2000, 2002, and 2018 in northern NSW). But this latest extraordinary situation raises many questions.
It is as if many of the major fires in the past are now being rerun concurrently. What is unprecedented is the size and number of fires rather than the seasonal timing.
The potential for large, intense fires is determined by four fundamental ingredients: a continuous expanse of fuel; extensive and continuous dryness of that fuel; weather conditions conducive to the rapid spread of fire; and ignitions, either human or lightning. These act as a set of switches, in series: all must be “on” for major fires to occur.
The NSW north coast and tablelands, along with much of the southern coastal regions of Queensland are famous for their diverse range of eucalypt forest, heathlands and rainforests, which flourish in the warm temperate to subtropical climate.
These forests and shrublands can rapidly accumulate bushfire fuels such as leaf litter, twigs and grasses. The unprecedented drought across much of Australia has created exceptional dryness, including high-altitude areas and places like gullies, water courses, swamps and steep south-facing slopes that are normally too wet to burn.
These typically wet parts of the landscape have literally evaporated, allowing fire to spread unimpeded. The drought has been particularly acute in northern NSW where record low rainfall has led to widespread defoliation and tree death. It is no coincidence current fires correspond directly with hotspots of record low rainfall and above-average temperatures.
Thus, the North Coast and northern ranges of NSW as well as much of southern and central Queensland have been primed for major fires. A continuous swathe of critically dry fuels across these diverse landscapes existed well before last week, as shown by damaging fires in September and October.
High temperatures and wind speeds, low humidity, and a wave of new ignitions on top of pre-existing fires has created an unprecedented situation of multiple large, intense fires stretching from the coast to the tablelands and parts of the interior.
More people in harm’s way
Many parts of the NSW north coast, southern Queensland and adjacent hinterlands have seen population growth around major towns and cities, as people look for pleasant coastal and rural homes away from the capital cities.
The extraordinary number and ferocity of these fires, plus the increased exposure of people and property, have contributed to the tragic results of the past few days.
How a bushfire can destroy a home
Communities flanked by forests along the coast and ranges are highly vulnerable because of the way fires spread under the influence of strong westerly winds. Coastal communities wedged between highly flammable forests and heathlands and the sea, are particularly at risk.
As a full picture of the extent and location of losses and damage becomes available, we will see the extent to which planning, building regulations, and fire preparation has mitigated losses and damage.
These unprecedented fires are an indication that a much-feared future under climate change may have arrived earlier than predicted. The week ahead will present high-stakes new challenges.
The most heavily populated region of the nation is now at critically dry levels of fuel moisture, below those at the time of the disastrous Christmas fires of 2001 and 2013. Climate change has been predicted to strongly increase the chance of large fires across this region. The conditions for Tuesday are a real and more extreme manifestation of these longstanding predictions.
Whatever the successes and failures in this crisis, it is likely that we will have to rethink the way we plan and prepare for wildfires in a hotter, drier and more flammable world.
The link below is to an article on how the warnings of fire chiefs in Australia have been ignored by governments across the country – meanwhile, the bushfire threat escalates.
Summer might be more than six weeks away, but out-of-control bushfires have already torn across parts of eastern Australia in recent days, destroying homes and threatening lives.
As of Wednesday afternoon, up to 30 homes were feared lost or badly damaged by bushfires burning in northern New South Wales. About 40 fires burned across the state.
This did not come as a surprise to meteorologists and fire agencies. Record-breaking heat and windy conditions were forecast for parts of NSW and Queensland this week, prompting severe fire danger ratings.
We’re often told the Australian bushfire season is starting earlier. This year it began in September on the eastern seaboard. Last year and in 2013, significant spring fires hit NSW and in 2015 they affected much of the nation’s southeast.
But what lies behind this phenomenon? We examined seasonal fire weather history for 44 years at 39 weather stations to find the precise answer.
This analysis is the most comprehensive ever conducted in Australia. It confirms the strength of the relationship between climate drivers such as El Niño, climate change, and the Australian bushfire season. It also demonstrates that a few milder bushfire seasons do not mean climate change isn’t happening.
Hot, dry, windy conditions spell fire trouble
The prerequisites for a severe bushfire season are high temperatures, low humidity, and strong winds that coincide with long periods of low rainfall.
These weather ingredients are used to calculate an area’s fire danger rating, using the Forest Fire Danger Index. The index produces a score reflecting the severity of fire weather on a given day, where zero represents minimal fire danger, 50 represents conditions where a fire ban may be issued, and 100 is considered potentially catastrophic.
Loss of human lives and property most often occurs on days when the index is high in a particular area. But strong seasonal fire weather doesn’t always translate to high-impact fires. Other factors in play include terrain, vegetation, ignition and the weather on the day.
In our research, we analysed the strength of the worst fire weather conditions to understand the relative severity of fire weather during different seasons and years, in relation to various climate drivers.
Why is fire weather so different every year?
Each of these climate drivers involves either changes to sea surface temperatures, wind movements, or both. They can all can affect temperature and rainfall patterns across the Southern Hemisphere, including Australia.
Our research confirmed that across the continent over more than four decades, climate drivers have affected the variability of Australia’s fire weather.
Of these drivers, the El Niño Southern Oscillation is the most influential. Weather during an El Niño phase is typically hot and dry, leading to worse seasonal bushfire conditions.
The positive phase of the Indian Ocean Dipole often coincides with El Niño and exacerbates its effects. This phase generally results in lower than average rainfall across southern Australia.
But when these two climate modes are in a negative phase, our research confirms that Australia often experiences more rain and milder bushfire conditions.
The modes evolve over many months and their effects on fire weather persist for several seasons. Their state during winter and spring is a strong indicator for the rest of the fire season for much of Australia.
The Southern Annular Mode refers to the north-south movement of strong westerly winds in parts of the Southern Hemisphere. When the mode is in a prolonged negative phase, fire weather conditions in Australia are worse – particularly in NSW. This effect is pronounced in winter and spring and means less rainfall and strong westerly winds.
The 2019 winter saw a persistent negative Southern Annular Mode, as did the 2013 and 2018 winter and spring seasons. There was a strong El Niño event and positive Indian Ocean Dipole in 2015. Australia’s bushfire season started earlier than usual in each of these years.
The converse is also true. In 2011 a strong La Niña (the opposite of an El Niño) resulted in milder bushfire seasons, as did the negative Indian Ocean Dipole of 2016.
Climate change is a culprit too
Long-term climate change in Australia is an undeniable reality. The State of the Climate 2018 report for Australia notes strong land surface temperature increases and a 10-20% decline in cool season rainfall across southern Australia since the 1970s. These changes are closely associated with increasing human greenhouse gas emissions, as well as natural variability.
The changed conditions has led to an average increase in the severity of seasonal bushfire weather across Australia – especially in southern parts of the continent. The increased severity affects all seasons but in particular spring, which means that, on average, the bushfire season is starting earlier.
Pulling it all together
Our research has made clear that climate modes bring large and rapid swings to the fire weather, while human-induced climate change gradually increases background fire weather conditions. The trend generally means an earlier start to the bushfire seasons than in the past.
Climate change is definitely playing a role in producing the earlier start to bushfire seasons and overall more extreme seasons, particularly in southeastern Australia. However, the natural variations in climate modes continue to play a key role, meaning we should not expect every bushfire season to be worse than the last as a result of climate change.
Similarly, a few milder bushfire seasons among a string of record high seasons does not mean that climate change should be dismissed.
Spring has barely arrived, and bushfires are burning across Australia’s eastern seaboard. More than 50 fires are currently burning in New South Wales, and some 15,000 hectares have burned in Queensland since late last week.
It’s the first time Australia has seen such strong fires this early in the bushfire season. While fire is a normal part of Australia’s yearly cycle and no two years are alike, what we are seeing now is absolutely not business as usual.
And although these bushfires are not directly attributable to climate change, our rapidly warming climate, driven by human activities, is exacerbating every risk factor for more frequent and intense bushfires.
The basics of a bushfire
For some bushfire 101, a bushfire is “an uncontrolled, non-structural fire burning in grass, scrub, bush or forest”. This means the fire is in vegetation, not a building (non-structural), and raging across the landscape – hence, uncontrolled.
For a bushfire to get started, several things need to come together. You need fuel, low humidity (which also often means the fuel itself has a low moisture content and is easier to burn), and oxygen. It also helps to have an unusually high ambient temperature and winds to drive the fire forward.
In Australia, we divide bushfires into two types based on the shape and elevation of the landscape.
First are flat grassland bushfires. These are generally fast-moving, fanned by winds blowing across flattish open landscapes, and burn through an area in 5–10 seconds and may smoulder for a few minutes. They usually have low to medium intensity and can damage to crops, livestock and buildings. These fires are easy to map and fight due to relatively straightforward access.
Second are hilly or mountainous bushfires. These fires are slower-moving but much more intense, with higher temperatures. As they usually occur in forested, mountainous areas, they also have more dead vegetation to burn and are harder to access and fight.
They burn slowly, passing through an area in 2-5 minutes and can smoulder for days. Fires in upper tree canopies move very fast. Mountainous bushfires actually speed up as they burn up a slope (since they heat and dry out the vegetation and atmosphere in front of the fire, causing a runaway process of accelerating fire movement).
Climate change and bushfire risk
To be clear, as previously reported, the current bushfires are not specifically triggered by climate change.
However, as bushfire risk is highest in warm to hot, dry conditions with low humidity, low soil and fuel load moisture (and are usually worse during El Niño situations) – all factors that climate change in Australia affects – climate change is increasing the risk of more frequent and intense bushfires.
Widespread drought conditions, very low humidity, higher than average temperatures in many places, and strong westerly winds driven by a negative Southern Annular Mode (all made worse by human-induced climate change) have collided right now over large areas of the eastern seaboard, triggering extremely unusual bushfire conditions – certainly catching many communities unawares before the start of the official bushfire season.
Different regions of Australia have traditionally experienced peak bushfire weather at different times. This has meant that individual households, communities and the emergency services have had specific periods of the year to prepare. These patterns now seem to be breaking down, and bushfires are happening outside these regular places and times.
New challenges for the emergency services
While experts recently forecast a worse-than-average coming bushfire season, the current emergency has essentially exploded out of nowhere.
Many Australian communities do know how to prepare but there is always some apathy at the start of bushfire season around getting households and communities bushfire-ready. When it’s still relatively cold and feeling like the last whisps of winter are still affecting us, bushfire preparation seems very far off.
Compounding our worsening bushfire conditions, we are increasingly building in bushfire-prone areas, exposing people and homes to fire. This tips the scales of risk further in favour of catastrophic losses. Sadly too, these risks always disproportionately affect the most vulnerable.
With such extensive fires over wide areas, the current emergency points to an extremely frightening future possibility: that emergency services become more and more stretched, responding to fires, floods, storms, tropic cyclones and a myriad other natural hazards earlier in each hazard season, increasingly overlapping.
Our emergency services do an amazing job but their resources and the energy of their staff and volunteers can only go so far.
Regularly the emergency services of one area or state are deployed to other areas to help respond to emergencies.
But inevitably, we will see large-scale disasters occurring simultaneously in multiple territories, making it impossible to share resources. Our emergency management workforce report they are already stressed and overworked, and losing the capacity to share resources will only exacerbate this.
Immediate challenges will be to continue funding emergency management agencies across the nation, ensuring the workforce has the necessary training and experience to plan and respond to a range of complex emergencies, and making sure local communities are involved in actively planning for emergencies.