Australia is essentially a desert continent, just looking at this satellite image, that is quite apparent. Because it lies in the latitudes between 15 degrees and 39 degrees south of the Equator, the tropics and subtropics. Globally speaking, deserts occur on all the continents in these general latitudes. Why is that? In a nutshell, warm ascending air near the equator, where convection (showers and thunderstorms) is most frequent, moves northward, and then descends at the subtropical latitudes. Air warms at roughly 10 degrees C per 1000 metres as it descends, and this also lowers the relative humidity, thus, areas of sinking air tend to be warm and dry. Deserts.
The only areas of Australia that receive more than 38 cm of precipitation are on the coastal margins in the southwest, far northern, and eastern and southeastern portions of the continent. Yet because of the presence of the large, hot, dry desert interior, even these moister continental margins can occasionally experience extreme heat waves when the desert air is pushed east and south by the right weather pattern.
The states of Victoria and New South Wales, in the far southeast, are particularly vulnerable to these extreme heat waves. Because of their latitudes further from the Equator, they normally have a more temperate climate, with average summer high temperatures of 24-30C. In addition, within 80-160 kilometres of the coastlines, annual precipitation is enough, 50-100 centimetres, or more, in the highest terrain, to support varied, dense, closed-canopy forests of mainly different Eucalyptus species.
Eucalyptus species trees have resins and oils in their leaves and wood that makes them burn very intensely. The combination of this, with the high fuel loading that occurs in the moister areas of Victoria and New South Wales, and the occasional extreme summer desert heat-waves, gives these areas the dubious distinction of having the greatest potential fire danger in the entire World.
Eucalyptus species trees have resins and oils in their leaves and wood that makes them burn very intensely. The combination of this, with the high fuel loading that occurs in the moister areas of Victoria and New South Wales, and the occasional extreme summer desert heat-waves, gives these areas the dubious distinction of having the greatest potential fire danger in the entire World.
Because Australia is a large land-mass, the size of the U.S. Lower 48 states, with only 22 million people, and hence, a smaller economy, their governmental operations are more limited than what you might expect. For this reason, over the past several years, meteorologists specialising in fire weather/fire danger forecasting in the U.S., have been requested by the Australian government, to assist with this type of forecasting, in the areas most vulnerable to wildfire, Victoria, New South Wales, South Australia, and Tasmania. They have their own highly qualified specialists in this area, of course, but staffing levels are somewhat limited, and during times of high fire danger/activity, having extra personnel on-hand makes a big difference. Since your lead author has been specialising in fire weather/danger forecasting since 1990, my turn to assist came up this past December, and I spent five weeks forecasting there, in the Sydney office, for the Australian Bureau of Meteorology.
Briefly, how this forecasting works, is that predicted maximum temperatures, minimum relative humidities, and wind speed/direction during the time of the max. temp., for all the different districts of each state (Sydney covers New South Wales, Melbourne covers Victoria, etc..) are entered in a spreadsheet. The computer keeps track of antecedent conditions, through different drought factors, and with these and the forecast for the next day's conditions, a Fire Danger Rating is computed. This is a number with ranges broken into categories, 0-10 is Low, 11-20 Moderate, 21-34 High, 35-49 Very High, and 50 or more, Extreme. If a value of 50 or more is calculated for the next day's Fire Danger Rating, a Fire WeatherWarning is issued, since the Fire Danger will be Extreme. This system is very efficient, works quite well, and accurately reflects the environmental conditions in each district.
When I arrived in Sydney to start my work assignment in mid-December, I was told by the staff there, that a slow season was expected, because it was not an "El-Nino" year, http://en.wikipedia.org/wiki/El_nino. And, sure enough, the last two weeks of December (equivalent of course to June in the northern hemisphere), were fairly cool and moist in New South Wales and Victoria. But, during January, short-term warm spells became more frequent and warmer, and I had to issue many Fire Weather Warnings during the first three weeks, when I was working there. My last day in Sydney, 1/24/09, was in fact, extremely hot, 40C (104F) or so, with gusty west winds blowing the hot continental desert air from west of the Blue Mountains, east over the city. So hot for me, that my personal warning lights were flashing, i.e., even with only minimal exertion, I was overheating.
When I arrived in Sydney to start my work assignment in mid-December, I was told by the staff there, that a slow season was expected, because it was not an "El-Nino" year, http://en.wikipedia.org/wiki/El_nino. And, sure enough, the last two weeks of December (equivalent of course to June in the northern hemisphere), were fairly cool and moist in New South Wales and Victoria. But, during January, short-term warm spells became more frequent and warmer, and I had to issue many Fire Weather Warnings during the first three weeks, when I was working there. My last day in Sydney, 1/24/09, was in fact, extremely hot, 40C (104F) or so, with gusty west winds blowing the hot continental desert air from west of the Blue Mountains, east over the city. So hot for me, that my personal warning lights were flashing, i.e., even with only minimal exertion, I was overheating.
By now, I'm sure you all have read or seen broadcast stories about the "bushfires" (the Australian term for wildfires) of February this year in the state of Victoria. The worst natural disaster ever to have befallen the country since it's founding. At least 210 fatalaties, thousands of homes and other structures, and even entire small towns, burned over. In excess of 365,000 hectares (900,000 acres) burned on the two worst days, 07 and 08 February.
http://en.wikipedia.org/wiki/2009_Victorian_bushfires
Why did this happen, and what can be learned from this tragedy?
Why did this happen, and what can be learned from this tragedy?
Drought conditions have been widespread in Southeast Australia for more than a decade. This is thought to be one of the manifestations of global warming. Because Australia is predominantly desert, with only small temperate margins on the southern fringes, these fringe areas are highly vulnerable. Climatic warming in summer is manifesting, and will continue to, as an increase of these heat waves in summer, with longer periods between cloudy and cooler weather caused by the passage of low pressure systems in the southern jet stream in the 40-60 degrees south latitude band. So, large areas of the Eucalypt forests have been moisture-stressed for many years.
Added to this then, an exceptional heat wave occurred in late January and February. All-time maximum temperature records were broken in many areas across the states of Victoria and Tasmania during this time, including the in second largest Australian city of Melbourne, which reached 46.4C (116F) on 07 Feb. The period of record there is 154 years.
These graphics show the departure from average of maximum temperatures during the two stages of the heat wave.
27-31 January, and...
the hottest day ever recorded at many sites in Victoria, 07 February.
The image to the right is from the Melbourne doppler weather radar, showing two of the large fire plumes on 07 February. On this day, the largest fire plume extended up to 18 KM, or 59,000 feet! Into the stratosphere. And it generated dozens of lightning strikes, which started more fires. The moisture release from the combustion of the vegetation, combined with the extremely strong updrafts in fire plumes, creates a "pyrocumulus" cloud, over larger fires. These are essentially thunderstorms in the stronger cases, and so may even produce hail and rain, besides lightning.
Radar picks up the ash and rain/hail in the plumes very well, and it proved highly useful to me during our record 2004 fire season here in Alaska.
Following is the lead page from the Australian Bureau of Meteorology's weather factors report of the tragedy: "Victoria experienced extreme fire weather conditions on Saturday 7 February that led to the tragic losses. A region of extremely hot air had persisted over inland South-eastern Australia since the last week of January and had resulted in several temperature records being exceeded.
The presence of a slow-moving high pressure system in the Tasman Sea, combined with an active monsoon trough, provided the conditions for dry hot air of tropical origin to be directed over the southern parts of the continent. On Saturday strong northerly winds, ahead of an approaching cooler south-westerly change, brought this hot air to southern Victoria. The combination of strong and gusty winds, low humidity and record high temperatures led to extreme fire conditions ahead of the change, while the change in wind direction exacerbated the dangers in fire behaviour.
The presence of a slow-moving high pressure system in the Tasman Sea, combined with an active monsoon trough, provided the conditions for dry hot air of tropical origin to be directed over the southern parts of the continent. On Saturday strong northerly winds, ahead of an approaching cooler south-westerly change, brought this hot air to southern Victoria. The combination of strong and gusty winds, low humidity and record high temperatures led to extreme fire conditions ahead of the change, while the change in wind direction exacerbated the dangers in fire behaviour.
The day was mostly sunny throughout Victoria, although some mid-level cloud did affect the southwest coast. The most extreme weather conditions were observed in the afternoon shortly ahead of the wind change. Maximum temperatures were up to 23 degrees (Celsius!) above the February average, and for many centres it was the hottest day on record. Melbourne city recorded 46.4°C, its highest maximum temperature since records began. Other places in the Port Phillip region recorded even higher temperatures including Avalon, which recorded 47.9°C. Victoria’s highest official recorded temperature on Saturday was 48.8°C (120 F) at Hopetoun in the Mallee region.
Wind gusts to 115 km/h were reported at Mt William and Mt Gellibrand, while gusts over 90 km/h were recorded at a number of sites including Port Fairy, Aireys Inlet, Kilmore Gap, Dunns Hill and Mt Hotham. After the change wind speeds in excess of 50 km/h continued to be observed for some hours."
As mentioned earlier, daily fire danger ratings of 50 are considered extreme. On February 7th, with temperatures of 38-47C (100-117F), relative humidities of 3-8 %, and winds of 36-60 kph (20-40 mph) or more, unprecedented values occurred. Fire danger ratings of 120 to 300 were recorded!
This created incredible fire behaviour. This image to the right are the remains of melted car wheels. To melt these aluminum alloy rims took temperatures of 900C (1650F) or higher. I saw the same thing when I worked at the South Canyon fire in Colorado in 1994, when 14 firefighters were killed. Ten of them were overtaken by a fire with temperatures like that, and where they fell was marked by the melted remains of their pulaski shovels. Many of the fatalities on 07 February occurred when people in their autos were overtaken on windy, narrow forested roads, by the fast-moving fires. Unimagineably terrifying and horrific occurrences of people being incinerated in their autos while bystanders/rescuers watched, but couldn't make it in time to their rescue, were reported.
What was it like for those who were trapped, or decided to try and save their home? The following is an eyewitness account:
"They warn you it comes fast. But the word fast doesn't come anywhere near describing it. It comes at you like a runaway train. One minute you are preparing, the next you are fighting for your home. Then you are fighting for your life. But it is not minutes that come between. It'
s more like seconds. The firestorm moves faster than you can think, let alone react.For 25 years we had lived on our hilltop in St Andrews, in the hills northeast of Melbourne. You prepare like they tell you every summer. You clear. You slash. You prime your fire pump. For 25 years fires were something that you watched in the distance. Until Saturday. We had been watching the massive plume of smoke in the distance from the fire near Kilmore all afternoon; secure in the knowledge it was too far away to pose a danger. Then suddenly there is smoke and flames across the valley, about a kilometre to the northwest, being driven towards you by the wind.
Not too bad, you think. I rush around the side of the house to start the petrol fire pump to begin spraying the house, just in case. When I get there I suddenly see flames rushing towards the house from the west. The tongues of flame are in our front paddock, racing uphill towards us across grass stubble I thought safe because it had been slashed. In the seconds it takes my mind to register the flames, they are into a small stand of trees 50m from the house. Heat and embers drive at me like an open blast furnace. I run to shelter inside, like they tell you, until the fire front passes. Inside are my wife, a 13-year-old girl we care for, and a menagerie of animals "rescued" over the year by our veterinary student daughter. They call it "ember attack". Those words don't do it justice.
It is a fiery hailstorm from hell driving relentlessly at you. The wind and driving embers explore, like claws of a predator, every tiny gap in the house. Embers blow through the cracks around the closed doors and windows. We frantically wipe at them with wet towels. We are fighting for all we own. We still have hope. The house begins to fill with smoke. The smoke alarms start to scream. The smoke gets thicker. I go outside to see if the fire front has passed. One of our two cars under a carport is burning. I rush inside to get keys for the second and reverse it out into an open area in front of the house to save it. That simple move will save our lives. I rush back around the side of the house, where plastic plant pots are in flames. I turn on a garden hose.
Nothing comes out. I look back along its length and see where the flames have melted it. I try to pick up one of the carefully positioned plastic buckets of water I've left around the house. Its metal handle pulls away from the melted sides. I rush back inside the house. The smoke is much thicker. I see flames behind the louvres of a door into a storage room, off the kitchen. I open the door and there is fire burning fiercely. I realise the house is gone. We are now fighting for our lives. We retreat to the last room in the house, at the end of the building furthest from where the firestorm hit. We slam the door, shutting the room off from the rest of the house. The room is quickly filling with smoke. It's black, toxic smoke, different from the super-heated smoke outside. We start coughing and gasping for air. Life is rapidly beginning to narrow to a grim, but inevitable choice. Die from the toxic smoke from inside. Die from the firestorm outside. The room we are in has french windows opening on to the front veranda. Somewhere out of the chaos of thoughts surfaces recent media bushfire training I had done with the CFA. When there's nothing else, a car might save you. I run the 30 or 40 steps to the car through the blast furnace.I wrench open the door to start the engine and turn on the airconditioning, as the CFA tells you, before going back for the others. The key isn't in the ignition. Where in hell did I put it? I rush back to the house. By now the black, toxic smoke is so thick I can barely see the others. We are coughing, gasping, choking. My wife is calling desperately for one of our two small dogs, the gentle, loyal Gizmo, who has fled somewhere in terror to hide. I grope in my wife's handbag for her set of car keys.
The smoke is so thick I can't see far enough to look into the bag.I find them by touch, thanks to a plastic spider key our daughter gave her as a joke. Our lives are saved by a plastic spider. I tell my wife time has run out. We have to get to the car. The choices have narrowed to just one option, just one slim chance to live. Clutching the second of our two small dogs, we run to the car.
I feel the radiant heat burning the back of my hand. The CFA training comes back again. Radiant heat kills. The three of us are inside the car. I turn the key. It starts. We turn on the airconditioning and I reverse a little further away from the burning building. The flames are wrapped around the full fuel tank of the other car and I worry about it exploding. We watch our home - our lives, everything we own - blazing fiercely just metres away. The heat builds. We try to drive down our driveway, but fallen branches block the way. I reverse back towards the house, but my wife warns me sheets of red-hot roofing metal are blowing towards us. I drive back down, pushing the car through the branches. Further down the 400m drive, the flames have passed. But at the bottom, trees are burning. We sit in the open, motor running and air-conditioner turned on full. Behind us our home is aflame. We calmly watch from our hilltop, trapped in the sanctuary of our car, as first the house of one neighbour, then another, then another go up in flames. One takes an agonisingly slow time to go, as the flames take a tenuous grip at one end and work their way slowly along the roof. Another at the bottom of our hill, more than 100 years old and made of imported North American timber, explodes quickly in a plume of dark smoke. All the while the car is being buffeted and battered by a galeforce wind and bombarded by a hail of blackened material. They sound like rocks hitting the car. The house of our nearest neighbour, David, who owns a vineyard, has so far escaped. But a portable office attached to one wall is billowing smoke. I leave the safety of the car and cross the fence. Where is the CFA, he frantically asks. With the CFA's help, perhaps he can save his house. I tell him we had already rung 000, before our own house burnt. Too man
y fires. Too few tankers. I leave him to his torment.
I walk back towards our own house in a forlorn hope that by some miracle our missing dog may have survived in some unburned corner of the building. Our home, everything we were, is a burning, twisted, blackened jumble. Through a gap in the back brick wall that used to be our bedroom window I see blackened mattress springs. Our missing dog Gizmo, Bobby our grumpy cockatoo, Zena the rescued galah that spoke Greek and imitated my whistle to call the dogs, our free-flying budgie nicknamed Lucky because he escaped a previous bushfire, are all gone. Killed in the inferno that almost claimed us as well. I return to the car and spot the flashing lights of a CFA tanker through the blackened trees across the road. We drive down the freeway, I pull clear more fallen branches and we reach the main road. I walk across the road to the tanker and tell them if they are quick they might help David save his house. I still don't know if they did. We stop at a police checkpoint down the hill. They ask us where we've come from and what's happening up the road. I tell them there's no longer anything up the road. We stop at the local CFA station in St Andrews. Two figures sit hunched, covered by wet towels for their serious burns. More neighbours. We hear that one old friend is missing. A nurse wraps wet towels around superficial burns on my wife's leg and my hand. We drive to my brother's house, which fate had spared, on the other side of town. The thought occurs to me - where do you start when you've lost everything? It doesn't matter. We escaped with our lives. Just. So many others didn't."
I feel the radiant heat burning the back of my hand. The CFA training comes back again. Radiant heat kills. The three of us are inside the car. I turn the key. It starts. We turn on the airconditioning and I reverse a little further away from the burning building. The flames are wrapped around the full fuel tank of the other car and I worry about it exploding. We watch our home - our lives, everything we own - blazing fiercely just metres away. The heat builds. We try to drive down our driveway, but fallen branches block the way. I reverse back towards the house, but my wife warns me sheets of red-hot roofing metal are blowing towards us. I drive back down, pushing the car through the branches. Further down the 400m drive, the flames have passed. But at the bottom, trees are burning. We sit in the open, motor running and air-conditioner turned on full. Behind us our home is aflame. We calmly watch from our hilltop, trapped in the sanctuary of our car, as first the house of one neighbour, then another, then another go up in flames. One takes an agonisingly slow time to go, as the flames take a tenuous grip at one end and work their way slowly along the roof. Another at the bottom of our hill, more than 100 years old and made of imported North American timber, explodes quickly in a plume of dark smoke. All the while the car is being buffeted and battered by a galeforce wind and bombarded by a hail of blackened material. They sound like rocks hitting the car. The house of our nearest neighbour, David, who owns a vineyard, has so far escaped. But a portable office attached to one wall is billowing smoke. I leave the safety of the car and cross the fence. Where is the CFA, he frantically asks. With the CFA's help, perhaps he can save his house. I tell him we had already rung 000, before our own house burnt. Too man
y fires. Too few tankers. I leave him to his torment.I walk back towards our own house in a forlorn hope that by some miracle our missing dog may have survived in some unburned corner of the building. Our home, everything we were, is a burning, twisted, blackened jumble. Through a gap in the back brick wall that used to be our bedroom window I see blackened mattress springs. Our missing dog Gizmo, Bobby our grumpy cockatoo, Zena the rescued galah that spoke Greek and imitated my whistle to call the dogs, our free-flying budgie nicknamed Lucky because he escaped a previous bushfire, are all gone. Killed in the inferno that almost claimed us as well. I return to the car and spot the flashing lights of a CFA tanker through the blackened trees across the road. We drive down the freeway, I pull clear more fallen branches and we reach the main road. I walk across the road to the tanker and tell them if they are quick they might help David save his house. I still don't know if they did. We stop at a police checkpoint down the hill. They ask us where we've come from and what's happening up the road. I tell them there's no longer anything up the road. We stop at the local CFA station in St Andrews. Two figures sit hunched, covered by wet towels for their serious burns. More neighbours. We hear that one old friend is missing. A nurse wraps wet towels around superficial burns on my wife's leg and my hand. We drive to my brother's house, which fate had spared, on the other side of town. The thought occurs to me - where do you start when you've lost everything? It doesn't matter. We escaped with our lives. Just. So many others didn't."
Gary Hughes is a senior reporter for The Australian
So, to sum up what happened in February, 2009 in Victoria, ten years of drought conditions, combined with an unprecedented heat wave, led to Australia's worst ever natural disaster, in terms of fatalities.
Unfortunately, climate change researchers using the most powerful computing facilities and most detailed global weather/climate modeling systems, are now saying that heat waves this severe, instead of occurring every few decades, will, within 30 years, be occurring every summer in Australia.
What about closer to home, here in the United States, has anything like this been occurring? Or will it?
The image to the left is a large rotating fire-whirl, on the Indians wildfire in Central California in June, 2008, in the Fort Hunter-Liggett area, inland from the Big Sur coast. This firewhirl took on the characteristics of an F1-scale tornado (wind speeds of 112-179 kph, or 73-112 mph). I was dispatched there last July as part of an investigatory team, to see what occurred/went wrong, because five firefighters in an engine on this road were injured when the firewhirl over-ran them.
Our team of veteran firefighters and researchers conducted extensive ground surveys and interviews of key personnel on the incident.
This image shows how the tornado-like firewhirl not just downed limbs from these large oaks, but pulled and sheared them off directly! Limbs that were 30 to 100 cm (1 to 3 feet) in diameter. It was highly fortunate no one was directly in those areas at that time!
This area of California had been in a record-breaking drought that winter/spring; almost no rain fell in March, which is usually the last wet month of their winter-rainfall season. Very little occurred also in April and May (it gets drier there by May normally anyway), such that by June, fire danger indices were at record high levels. This, combined with a weather day when exceedingly dry air aloft was mixed down to the surface under strong high pressure ridging, combined with terrain interactions, led to the extreme fire behaviour, manifesting as a rotating plume, or firewhirl. It was highly fortunate that there were no fatalities.
Many veteran wildfire specialists I have spoken with have told me that they are seeing more intense fire behaviour throughout the western U.S., than say, 20 to 30 years ago. Fires are burning more intensely, and more often, through the night. This is due to the long-term droughts the western U.S. has been experiencing, killing large swaths of forest stands, combined with warmer summer temperatures caused by stronger high pressure systems (which also contain very dry air).
How about here in Alaska?
This chart is a plot of annual average summer temperatures in Fairbanks, on top, combined with the seasonal fire acreages, divided by 100,000. The period of record extends back to 1955. Note how the higher years are occurring more frequently now, in the past 25 years, and the slowly increasing temperature trend. Our record high fire year of 2004, which was also the warmest summer recorded in Fairbanks, was followed in 2005 by the third highest acreage loss. 
Before going further, let's take a quick look at what happened here in Alaska during the summer of 2004. The may-august average temperature was 16.2C (61.2F), about 3.2C (6F)above average. It was also the 2nd driest ever over most of the Alaska interior, the month of August, normally the wettest, was nearly rainless. Extreme drought stress occurred in the boreal forest species, black and white spruce, and birch/aspen/balsam poplar. So much so, that even the deciduous hardwood trees exhibited fire behaviour approaching that of the normally flammable black spruce (referred to by Alaska wildland firefighters as "gasoline on a stick").
When forecasting weather, meteorologists assess temperatures, humidities, and winds at different standard levels of the atmosphere, which are measured twice-daily world-wide by radiosonde balloons. This data is input to the Numerical Weather Prediction models, which model the atmosphere through hundreds of quantitative descriptors of physical processes, using trillions of calculations per second, on supercomputers. These models generate forecast charts out to ten days of various levels in the atmosphere (though only the first 3-5 days of course are usually very accurate). One of these standard levels that is assessed is 850 millibars (mb). The main parameter assessed is the height at which the pressure equals 850 mb, which is a function of temperature. The warmer the airmass, the higher that height is, and the colder, the lower it is. This level is usually around 1450-1550 metres (4600-5100) feet here in Alaska.
This plot, to the left, is of 850 mb temperatures over the past year, measured by radiosonde balloon released from Fairbanks, along with means, records, and standard deviations, for each day. The period of record is from 1948-present. One thing that stands out, is how variable these are. Inter-annual and seasonal variability is very high in the higher latitudes, since any shift in jet stream position or intensity highly affects these regions. The warmest measured 850 mb temperatures over Fairbanks were 20C (68F).
The most active several days during the record-breaking 2004 Alaska fire season were during a northeast-wind event in late June and early July. 850 mb temperatures at this time were around 16C (61F). Remember, this is at 1500 metres. When air is forced to descend, as it does during high-pressure ridging episodes like the northeast wind-event of late June/early July 2004, it warms at 10 degrees C per 1000 metres. Thus, if the 16C air at 1500 metres descends to near sea level (much of the Alaska interior is at elevations of only 60-250 metres msl), it would theoretically warm to 31C (88F). Factor in solar heating of the ground, and you can add a degree or two. Temperatures weren't quite that warm on those days in 2004, because thick smoke blown out ahead of the fires shaded the region, and kept temperatures 3-6C cooler.
The most active several days during the record-breaking 2004 Alaska fire season were during a northeast-wind event in late June and early July. 850 mb temperatures at this time were around 16C (61F). Remember, this is at 1500 metres. When air is forced to descend, as it does during high-pressure ridging episodes like the northeast wind-event of late June/early July 2004, it warms at 10 degrees C per 1000 metres. Thus, if the 16C air at 1500 metres descends to near sea level (much of the Alaska interior is at elevations of only 60-250 metres msl), it would theoretically warm to 31C (88F). Factor in solar heating of the ground, and you can add a degree or two. Temperatures weren't quite that warm on those days in 2004, because thick smoke blown out ahead of the fires shaded the region, and kept temperatures 3-6C cooler.
This chart to the left is from the Arctic Climate Impact Assessment. This report was an internationally collaborative study of climate change that has already occurred in the Arctic, combined with climate change modeling depictions of future changes.
Many of the researchers involved work here in Fairbanks at the University of Alaska.
What this is showing, is that by 2050, the average of the different climate change models predicts a 2.5 degrees C or so (4.5 degrees F) average warming over the Arctic region.
What does this mean for interior Alaska? Well, if we currently could experience a 20C temperature at 850 mb during an extreme warm spell/high pressure ridging episode, in 2050, that would likely be 23C, or more, in a similar event. That would translate to lower-elevation temperatures in the mid 30s to low 40s C (mid 90s to mid 100s F)! In addition, if the average may-august summer temperatures around Fairbanks warm from the current 13C or so, to 16C, the health of the spruce forests will be compromised. White and black spruce in the Alaska boreal forests shut down their growth when average growing-season temperatures reach 16C, and become vulnerable to insect predation and disease mortality. So, with temperatures in the 30s to low 40s C, and large swaths of dead and dying spruce trees, in another 2004-like drought year, I think it would be safe to say that unprecedented fire behaviour would occur. It's not a matter of if, but when this will occur.
What does this mean for interior Alaska? Well, if we currently could experience a 20C temperature at 850 mb during an extreme warm spell/high pressure ridging episode, in 2050, that would likely be 23C, or more, in a similar event. That would translate to lower-elevation temperatures in the mid 30s to low 40s C (mid 90s to mid 100s F)! In addition, if the average may-august summer temperatures around Fairbanks warm from the current 13C or so, to 16C, the health of the spruce forests will be compromised. White and black spruce in the Alaska boreal forests shut down their growth when average growing-season temperatures reach 16C, and become vulnerable to insect predation and disease mortality. So, with temperatures in the 30s to low 40s C, and large swaths of dead and dying spruce trees, in another 2004-like drought year, I think it would be safe to say that unprecedented fire behaviour would occur. It's not a matter of if, but when this will occur.
This is what is already what is occurring in Australia. Will we be ready? It seems unlikely, given current political and economic realities, that atmospheric CO2 and methane emissions will be cut back enough to prevent this kind of scenario from occurring in the Western U.S. and Canada, as well as Alaska.
