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Claim
Bjorn Lomborg says forest fires have come down globally.
Fact
Lomborg used data shown in isolation from a study to mislead about global burned areas as confirmed by the lead author of the study. There is a greater scientific consensus including by NASA that forest fires are increasing globally due to climate change.
What they claim
Danish political scientist and a known climate science contrarian, Bjørn Lomborg, recently posted on Twitter, a graph claiming that NASA’s satellite data from 2001 to 2022 shows that the instances of forest fires have come down and haven’t been on the rise due to climate change. Here’s the tweet:
The graph shared in the tweet shows burned area per year and the percentage of global land.
In his post, Lomborg also shared the link to a study by Prof Louis Giglio and Dr Mike Humber from the University of Maryland. The study explains how the data of burned areas is put together.
What we found
The claim is misleading. Burnt areas are expanding and contrary to the claim, climate change is leading to more frequent and fierce fires worldwide.
Since the post cites NASA data to claim that forest fires have come down, we ran a keyword search concerning this. We found a NASA article from 2017 stating that their data from 1998-2015 show that wildfires have come down globally.
However, it states, “The impact of human-caused changes in savannas, grasslands and tropical forests is so large that it offsets much of the increased risk of fire caused by warming global temperatures, said Doug Morton, a research scientist at Goddard and a co-author of the study. Still, the impact of a warming and drying climate is seen at higher latitudes, where fire has increased in parts of Canada and the American west. Regions of China, India, Brazil and southern Africa also show an increase in burned area. But the expansiveness of savannas and grasslands puts the global trend in decline.”
Next, we also came across this recent video on the official YouTube channel of NASA that says changes in our climate, along with other factors, have led to wildfires increasing in intensity, severity, size and duration. NASA climate and wildfire expert Liz Hoy explains in the video how and why NASA studies these events from the ground, air, and space to better understand the impacts they have on both a local and global scale.
About the study shared in the Twitter post
The tweet mentioned a study which explains the methodology of how the data is put together. The lead author of that study, Prof Louis Giglio, speaking to The Guardian about the Lomborg post explained: “The global burned area time series shown in isolation is misleading because it is dominated by Africa, where most of the burned area worldwide is located and where regular burning has been a normal part of the environment for millennia.”
Giglio also stated that the contribution from smaller fire-prone and heavily populated regions like California and parts of Australia, where fire intensity and burned area are increasing, was dwarfed in the data shared adding that Africa accounted for about 67% of the burned area globally, and the reduction in burn area in the last 15 years was due mostly to natural variability in the weather that had seen more rain, as well as the expansion of croplands.
The Guardian article also quoted Dr Grant Williamson, a bushfire expert at the University of Tasmania, as saying that Dr Lomborg’s claim about global burnt area as declining is ‘misleading if not understood in the true context of global fire activity.’
“Taken as a whole, fire activity has declined globally, but that change is primarily occurring in tropical savanna systems, which are the most fire-prone on Earth and have an outsized influence on the global total. Decline in those systems is driven by human land-use change, such as the increase in agricultural activity and the shift in population to cities,” Dr Grant said.
“It is clear that within temperate and boreal forest, including Europe, Australia and North America, burnt area is increasing, fires are becoming more frequent and intense, and extreme fire weather is becoming more common,” Dr Grant further added.
Climate Change and Wildfires
The probability and size of wildfires worldwide have grown over the past few years due to climate change. Wildfire seasons have broken records recently, especially in 2022 Australia, the Arctic, the European Union, and North and South America.
According to a National Geographic article, hot and dry conditions during heatwaves help fires spread at a faster rate and also burn longer and with more intensity. Warmer air temperatures dry the forests and other vegetation by soaking up water. Intense record-breaking heat waves can cause major crisping of burnable material that can ignite easily. When ignition happens, even if the reason is natural, the chances of it turning into a big fire are much higher now with climate change.
Speaking to Reuters, Friederike Otto, a climate scientist at Imperial College London who also co-leads the World Weather Attribution research collaboration said, “Every heatwave that what we are experiencing today has been made hotter and more frequent because of climate change”. The same article states that to find out exactly how much climate change affected a specific heatwave, scientists conduct “attribution studies”. Since 2004, more than 400 such studies have been done for extreme weather events, including heat, floods and drought – calculating how much of a role climate change played in each. For example, scientists with World Weather Attribution determined that a record-breaking heatwave in western Europe in June 2019 was 100 times more likely to occur now in France and the Netherlands than if humans had not changed the climate.
A report published in 2022 by the UN Environment Programme (UNEP) and GRID-Arendal says climate change and land-use change are projected to increase wildfire frequency and intensity, with a global increase in extreme fires of up to 14% by 2030, 30% by the end of 2050, and 50% by the end of the century.
In India too, a 10-fold rise in intense forest fires happened from 2000 to 2019. It has been found that the intensity and frequency of forest fires have increased significantly in the last decade or so. According to the study, ‘Managing Forest Fires in a Changing Climate’, by the Council on Energy, Environment and Water (CEEW) the number of months in which forest fires generally occur also increased in the last two decades or so. More than 62 per cent of Indian states are prone to high-intensity forest fires and Andhra Pradesh, Assam, Chhattisgarh, Odisha and Maharashtra are the most prone, the study found.
Burned area per year is the important metric. After a fire, an area is left as a wasteland, and it will take decades for it to recover. In essence, the most threatened locations have vanished and are no longer able to contribute to the graph.
References:
https://www.profor.info/sites/profor.info/files/PROFOR_ManagingWildfires_2020_final.pdf
https://www.unep.org/resources/report/spreading-wildfire-rising-threat-extraordinary-landscape-fires
https://www.edf.org/climate/heres-how-climate-change-affects-wildfires
https://www.sciencedirect.com/science/article/pii/S0034425718303705
https://www.nasa.gov/feature/goddard/2017/nasa-detects-drop-in-global-fires
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