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GS Paper III

News Excerpt:

In 2023, wildfires globally released 7,330 million tonnes of CO2, according to the EU’s Copernicus Atmosphere Monitoring Service (CAMS).

• This surpasses the 6,000 million tonnes of greenhouse gases (CO2 and other gases) emitted by the US in 2022.

More About News

• In Canada, which contains 9% of the world’s forests, significant fires were reported as early as May 9, prompting evacuations in several towns in British Columbia and Alberta.
• By mid-May, these fires had already released an estimated 55 million tonnes of CO2 into the atmosphere.
• As of May 15, 2024, 11 countries reported wildfires.

The intensity of wildfires 

• The May 2024 North American Seasonal Fire Assessment and Outlook, issued by government agencies in the US, Canada, and Mexico, indicates that current warm, dry, and windy conditions could spark additional wildfires.
• This raises concerns that the 2024 Canadian wildfires might replicate the record-breaking 2023 event, which destroyed 18.4 million hectares—an area larger than Greece—and released 1,760 MtCO2.

Role of Global Warming

• Over the past four decades, global warming has created conditions conducive to more frequent and intense wildfires.
• Wildfires are also spreading to new areas. A study found that fires in the western US have spread to higher elevations, where they have historically been rare, due to warmer and drier conditions.
• The increasing frequency and intensity of wildfires also hinder forests' ability to regrow and absorb emissions.
• However, climate change creates a feedback loop. Hot temperatures lead to extreme weather and droughts, worsening wildfires and injecting more CO2 into the atmosphere, which in turn traps more heat.

Wildfire Emissions

• The true wildfire emissions could be even higher due to the complexity of calculations, which are likely underestimated.
• Calculating wildfire emissions is intricate, influenced by variables such as temperature, wind, humidity, and drought, which vary greatly and unpredictably.
• Traditionally, 80% of the carbon released during a wildfire is reabsorbed by new vegetation, while the remaining 20% contributes to atmospheric CO2.

Assessment Difficulties

• The margin of error for wildfire-related CO2 emissions can be as high as 20%. 
• In contrast, the uncertainty for CO2 emissions from fossil fuel combustion is around 6%.
• The UN Intergovernmental Panel on Climate Change (IPCC) guidelines for national greenhouse gas inventories state that scientists need to know four factors to compute wildfire emissions:
• The burned area's extent,
• The biomass density or vegetation in the burned area,
• The emission factor (mass of pollutant produced per unit dry mass of fuel burned), and
• The combustion factor (amount of charcoal left after wood is burned).
• India and many other countries use the IPCC guidelines to estimate wildfire emissions.

Global Fire Assimilation System (GFAS)

• The GFAS used by EU’s CAMS employs a different approach, based on the fire radiative power (radiant heat released from detected fires in megawatts from satellite data).
• It measures the brightness temperature anomalies in different parts of the infrared spectrum. A high anomaly indicates a heat source.

Moderate Resolution Imaging Spectroradiometer (MODIS)

• The most widely used tool to measure fires is the MODIS on two NASA satellites, Terra and Aqua, which scan the Earth’s surface at least once every day or two.
• But fires that occur outside of those measurement times can not be measured by this method. 

Geostationary Satellites

• Another option is using geostationary satellites, positioned in a circular orbit at the Earth’s equator, which record the same image at brief intervals, useful for weather observations.
• However, the image resolution suffers because they are stationed about 36,000 km from the Earth’s equator.

Differences in Assessment

• The study of 2021 concludes that current global burn estimates based on sensors like MODIS should be viewed as very conservative.
• The team analyzed new images from the European Space Agency’s Sentinel-2 satellite and found 4.89 million square kilometers (km²) of land burned in Africa in 2016, about 16% of the continent’s total area, compared to MODIS’ detection of only 2.72 million km² burned area in the same year.
• About 87% of the difference was attributed to the inclusion of small fires.

Smoldering Wildfires

• Another source of uncertainty is smoldering fires, the slow, low-temperature, flameless burning of vegetation.
• Smoldering wildfires have received little attention but are a global concern because they emit large amounts of carbon and are difficult to detect and suppress.
• Smoldering is predominantly observed in peatlands, a type of wetland built of partially decayed plant matter.
• Covering only 3% of the world’s landmass, peatlands exist across 180 countries and store at least twice as much carbon as any other vegetation type.
• Fires in peatlands can reach deep layers several meters below the surface, making it difficult to assess the extent of the damage.

Technique used for Assessment

• Emission factors also add to uncertainties. These are derived from laboratory- or field-based experiments.
• Some Scientists conduct field surveys to capture smoke in bags, which are then analyzed in a lab to calculate CO2 emissions from a given mass. Some researchers use airplanes to sample smoke plumes.

Wildfire in India

• India’s Third Biennial Update Report to the UN Framework Convention on Climate Change states that emissions from forest fires contribute only 1-1.5% of all global emissions from wildfires, despite having about 2% of the world’s forest area.
• The report warns that this could change with climate change as temperature rises would dry out vegetation, making it more fire-prone, especially in Himachal Pradesh and Uttarakhand.

BBURNED project

• In December 2022, the International Global Atmospheric Chemistry community initiated the Biomass Burning Uncertainty: Reactions, Emissions, and Dynamics (BBURNED) project.
• It aims to better quantify uncertainty and variability in biomass burning emission estimates by coordinating international scientific efforts to understand current and future impacts of wildfires on public health and climate.
• BBURNED held its first workshop in November 2023, focusing on emissions inventories and methodologies.
• The next workshop in September 2024 will discuss fire emissions and modeling to foster collaboration and data sharing.