The climate crisis is fuelling more intense wildfires

Around the world, the number and intensity of wildfires is on the rise, and the Arctic and sub-Arctic regions have been among the hardest hit. As SUSANA HANCOCK writes, these fires send some of the world’s most dense carbon stores up in smoke, with ramifications for human health, the world’s climate and the Arctic itself.

These more energetic fires have doubled in strength and size over the past two decades, consuming more fuel and releasing more heat. As a result, they are associated with both greater emissions and more social, ecological and economic losses, whether direct or indirect. In the Arctic and sub-Arctic boreal and temperate forests, the intensity of wildfires increased 7.3-fold and 11.1-fold, respectively, from 2002 to 2023 (as measured by the heat energy they release).

In Russia this year, notable fires were burning by early June. By mid-month, a state of emergency had been declared in Sakha and Tuva provinces. Elsewhere in Siberia, cumulative emissions from abnormally strong fires in places like Amur Oblast had already surpassed any June or July record in the 22 years of monitoring by the Copernicus Atmosphere Monitoring Service. These emissions triggered air quality warnings across Mongolia, China and Japan. The year 2024 is continuing a trend that has seen six of the most powerful wildfire years occur within the past seven.

Russia’s emergency situations minister, Alexander Kurenkov, has stated that even though Siberia has experienced 30 per cent fewer fires this year than in 2023 (so far), the area burned is 50 per cent larger.

A region under pressure

The pace of climate change in the Arctic is eclipsing that of other areas in terms of warming and new patterns of heat and moisture. Higher temperatures and more arid conditions are making the region increasingly susceptible to large-scale wildfires with more significant emissions. Boreal forests are some of the most carbon-rich landscapes on Earth, with as much as 80 to 90 per cent of their carbon stored below ground. Much of the boreal carbon has been protected from past burns, but these hotter fires burn more deeply into the soil, releasing carbon that has been stored for millennia.

Recent studies highlight several climate trends that are driving these more powerful burns and indicate the reach of their influence. For example, some show connections between heat waves in continental Europe and large-scale fires throughout the circumpolar region. One study found that drier conditions as a result of human-induced climate change fuelled more than 50 per cent of the rise in fire activity in the United States.

Zombie fires and feedback loops

Not only is the Arctic warming four times faster than the rest of the planet, but night-time warming is outpacing daytime warming—another change that fuels fires. Overnight cooling periods traditionally allow fire growth to ebb, but fires are able to maintain more energy overnight as the temperature differential shrinks.

In addition to fires gaining ground overnight, an increasing number are overwintering. The carbon-infused soils feed holdover fires (also known as zombie fires), which smoulder throughout the winter—burning more of the stored carbon—before reigniting on the surface in the spring.

Emitting climate-altering gases like carbon dioxide, methane, nitrous oxide and others—which beget further warming and conditions conducive to burning—is one way in which wildfires stoke feedback loops in the Arctic. But researchers have described another feedback loop in which wildfire soot deposits on Arctic ice and snow speed up melt and lower their albedo. (Albedo is a measure of how much sunlight a surface reflects. When bright ice and snow are covered by dark soot, they absorb more heat and melt faster.)

And although the degree of causation remains unconfirmed, smoke from forest fires in Québec, Canada in 2023 reached southwestern Greenland. This coincided with an anomalous warm period in the region and significant melting of the ice sheet.

A harm without boundaries

Smoke—like all forms of air pollution—is transboundary. It affects areas far beyond the source.

In addition to its consequences for ecosystems, wildfire smoke is toxic to human health. It comprises particulates, heavy metals, acids and other compounds that pollute waterways and farmland and harm air quality. In people, such pollution is linked with millions of premature deaths and a range of health conditions, including cardiovascular, respiratory and cognitive diseases.

Direct losses associated with fatalities in eastern Siberia and East Asia from Siberian fires alone have been estimated by researchers to exceed US$10 billion a year. Indirect health and economic costs, such as those associated with illness and lost productivity, could be much higher.

Extreme fires are just one of the rapid changes affecting the northern regions of the planet. With yet another consequential wildfire season underway in the temperate and boreal forests of Siberia, carbon once buried deep in the ground is on a trajectory to amplify pollution, with cascading impacts on health, ice and the atmosphere for years to come.

To stop the severe escalation in wildfires and pollution, the world must reduce its dependence on fossil fuels. Commitments to halving emissions by 2030 and reaching net zero by mid-century need to be enforced so we can reach the goals set by the Paris Agreement with little overshoot.