In their jargon, scientists call this phenomenon "positive feedback loop". More prosaically, we would probably speak of a vicious circle. In Australia, the current fires have emitted as much CO² in a few weeks as the 100 least polluting countries do in a year.
According to the Carbon Brief website, nearly 400 million tonnes of carbon dioxide escaped from these deadly forest fires between September and the beginning of January. This is roughly the quantity produced by the United Kingdom over the whole of 2018.
The ongoing #AustralianFires have already released more CO2 than the combined annual emissions of more than 100 countries put together… pic.twitter.com/H0TD2uHr0T
- Carbon Brief (@CarbonBrief) January 10, 2020The spread of this greenhouse gas into the atmosphere is one of the main causes of global warming. Cruelly, the fires therefore have the effect of further accentuating climate change, which itself favors this type of disaster.
This phenomenon highlights the issue of pollution caused by forest fires and its consequences for humans. "We must not forget that the burnt forest no longer exists for years," points Serge Zaka, doctor in agroclimatology. It can therefore no longer absorb the C0² emitted by the surrounding pollution ... ”
"Major stress"
Forest fires are certainly an integral part of the Australian ecosystem. But the fires of recent weeks stand out for their scale and duration, which experts attribute in part to global warming. Some forests around Sydney, for example, have been almost 80% burned.
This "major stress" considerably lengthens the regeneration time of the natural environment. It is estimated that it would take "20 to 30 years", with the help of man, for life to resume its normal course. Deprived of these wooded areas, local populations are subject to critical levels of pollution.
In addition to CO², fires release a lot of fine particles, particularly dangerous for health. Below 10 nanometers in diameter, these suspended particles, which are associated a lot, in big cities, with the use of diesel, enter the lungs.
Canberra, the most polluted city in the world
They therefore pose a particularly serious risk to pregnant women, children, the elderly and the sick suffering from cardiovascular or respiratory diseases, diabetes and obesity. In early January, Canberra, 380,000 inhabitants, became the most polluted city in the world, forcing the authorities to distribute hundreds of thousands of pollution masks.
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The immense forest fires also have the particularity of releasing "pyrocumulonimbus", clouds generated by heat sources, as certain volcanoes or nuclear bombs do. In the short term, these plumes of smoke can trigger thunderstorms themselves, which cause new outbreaks of fire, in previously untouched areas.
This type of pollution moves quickly and eventually dissolves in the rains. Conversely, part of the mass-produced fine particles will reach the stratosphere, 15 kilometers above the ground. There, no precipitation can reach them, nor prevent their movement.
They will then constitute a light veil around the globe which will return a tiny but not negligible part of the sun's rays towards space. Counterintuitively, this phenomenon, observed after the major fires of the 20th century, therefore tends to cause the global temperature to drop by a few tenths of a degree.
If it may seem like good news, this disruption shows how these huge fires can have consequences on a terrestrial scale, not to mention the damage to biodiversity they cause. They also recall the need to analyze them with these repercussions in mind. Before Australia, Colombia, the Amazon or Siberia had already experienced record forest fires in 2019.
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