19

A definitive statement comes from the abstract of Scott and Glasspool1, 2006: Charcoal, a proxy for fire, occurs in the fossil record from the Late Silurian (≈420 Myr) to the present. One of the tired old truisms you learn is that fire needs three things: Oxygen, fuel, and a source of ignition. There is little doubt that there has been lightning since ...


12

It's a combination of both the density and amount of smoke in the air and ash produced by the fire. The thing about cold fronts and bush fires is they make the conditions for fire worse by pushing hot air in front of them. They have been blamed for the severity of the bush fires in Victoria in 2009, 1983 and 1939.


9

Right. We can make some estimates of the scale of the problem, but they will come with a healthy margin of error. If we assume that wood has a calorific value of 18.5 GJ/t (from the phyllis2 database) The area burned is 18.6 Mha (from Wikipedia here) The standing volume of material is circa 1500 m3/ha (an educated guess based on Eucalyptus values in Forest ...


6

As of 7 January 2020, the total area burnt by the fires in the whole of Australia is 8.4 million hectares (21 million acres; 84,000 square kilometres; 32,000 square miles. That is equivalent in area to the nations of Austria or the United Arab Emirates. Greater in area than the Czech Republic, Ireland or Sri Lanka. The vast majority of that has been on the ...


6

Revised answer TL;DR After having just heard from two experts who actually work in this field(firestorms and dry lightning) in Australia I believe the lightning seen is what is known as "dry lightning" comes from isolated thunderstorms and sometimes storms associated with minor troughs and fronts that come through Australia and also originating from a ...


4

Most fires are probably in the periphery because they are started by humans. They encroach on the jungle from the outside, where they already live, and there are roads instead of impenetrable jungle.


4

EDIT: As pointed out by Jean-Marie Prival and klanomath in the comments, I originally misread the specific heat of wood as per tonne, rather than per kilogram, and also used the wrong conversion between TWh and TJ. Here are my rough calculations, based on CO2-release estimates from NASA: 306 MtCO2 (wikipedia) Wood spec energy = 4.50 kWh/kg (...


4

For now it seems to be average, at least compared to the last decade. The National Interagency Fire Center has a page with a year-to-date statistics table. You can see that so far, the values for 2020 are pretty similar (even slightly below) to the 10-year average, both in terms of number of fires and burned acres. 2020 | Fires: 41,599 | Acres: ...


3

After Saint Helens, forest managers thought to harvest timber in the area and replant it because they assumed nothing would ever grow again. Instead they left it alone and the eruption epicenter is now the largest outdoor ecological restoration experiment. Scientists monitor it's rate and aspects of it's regeneration. Contrary to being a dead sterile ...


3

Falling ash is usually not a concern for agriculture. But the particulate matter (smoke) can harm agricultural products. Not through the soil, but by exposing the plants to smoke over long periods. In particular, many vineyard owners are very unhappy with the recent increase in wildfire smoke in the west. It taints their grapes and makes the wine less ...


3

For now the destruction of the US Pacific wild fires is well above average. As of 11 September 2020, the fires have obliterated California’s record for the number of acres burned in a year. Six of the top 20 largest fires in state history have occurred in 2020, according to Cal Fire. The reasons for the fires are, Lightning initially triggered many of the ...


3

The total area burned was 12.6 million hectares, or 126,000 square kilometers. This is equivalent to: The US state of North Carolina (125,920 sq km) The US state of New York (122,057 sq km) The US state of Mississippi (121,531 sq km) North Korea (120, 408 sq km) 96% of Greece (130,647 sq km) 52% of the United Kingdom (241,930) 36% of Germany (348,672 sq km) ...


3

There was an interesting paper on this for the United States a couple of years ago: Balch et al (2017) Human-started wildfires expand the fire niche across the United States, PNAS, doi: 10.1073/pnas.1617394114 They estimate that in the coterminous U.S. human-started events account "for 84% of all wildfires and 44% of total area burned". There is a marked ...


2

My personal experience of rainforest is confined to Malaysia, where it is too damp to burn unless it is first cut down and allowed to dry out in the sun. The fires on these ladangs, as they are called, never spread to nearby rainforest, and abandoned ladangs eventually become rainforest again. I have some knowledge of other rainforests and have come to the ...


2

It was a combination of thick smoke and pyrocumulus clouds. Possibly there might have been other types of cloud as well, Ash rising on the updraught may also have been a factor. I am informed that normal types of cloud sometimes made an appearance during the drought. Near-pitch darkness in daylight hours is also characteristic of volcanic eruptions, but I am ...


1

If you think how white smoke looks when it is rising elsewhere and you are looking at sunlight reflecting off it ... what you are then seeing, is some of the light that the folks who have that smoke between them and the sun are not getting. Smoke will also absorb a lot of sunlight (and re-radiate it as infra-red), especially if it's sooty black smoke rather ...


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