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Novel Technique Detects an Alarming Volume of Methane Emissions from Wildfires

UC Riverside researchers have recently utilized a novel detection technique to uncover an alarming volume of methane emissions from wildfires, a potent greenhouse gas. Intriguingly, this emission source has not been previously considered in the assessments of state air quality regulators.

The researchers at UC Riverside have determined that methane, known to be 86 times more potent than carbon dioxide in terms of warming the planet over a 20-year timeframe, is being emitted in substantial quantities from wildfires. These emissions, previously unrecognized by state air quality managers, pose a significant challenge to achieving cleaner air and climate goals as mandated by regulations. It is crucial for policymakers to account for this previously unacknowledged source of methane in their efforts to combat climate change effectively.

While it is not uncommon for wildfires to release methane, a recent study by UC Riverside has revealed a staggering increase in methane emissions from the top 20 fires that occurred in 2020. Surprisingly, the amount of methane emitted from these wildfires was found to be over seven times higher than the average emissions from wildfires in the previous 19 years. This alarming finding underscores the urgent need for heightened attention and action to address the growing impact of wildfires on methane emissions, which contribute significantly to greenhouse gas emissions and climate change.

Francesca Hopkins, co-author of the study and a professor of environmental sciences at UC Riverside, emphasized that wildfires are becoming increasingly larger and more intense, resulting in higher emissions. In fact, the wildfires that occurred in 2020 were responsible for emitting an amount of methane that would have accounted for 14 percent of California's methane budget, had it been accurately tracked. This highlights the pressing need to include wildfires as a significant source of methane emissions in monitoring and management efforts to effectively mitigate the impact of these emissions on the state's overall greenhouse gas emissions and climate change goals.

Although the state currently does not monitor natural sources of methane, such as emissions from wildfires, the recent study by UC Riverside indicates that wildfires in 2020 would have ranked as the third largest source of methane emissions in California. This underscores the significant contribution of wildfires to methane emissions, despite not being actively tracked by the state. It emphasizes the need for a comprehensive approach to accounting for all methane emission sources, including wildfires, in order to effectively address and mitigate the impact of this potent greenhouse gas on the state's overall emissions and climate change efforts.

Professor Francesca Hopkins, who co-authored the UC Riverside study, highlighted the challenges in measuring and controlling emissions from sources like wildfires. However, she emphasized the importance of making efforts to account for these emissions, as they can offset the progress being made in reducing other methane sources. While natural sources of methane emissions, including wildfires, may be difficult to control, it is crucial to include them in mitigation strategies to effectively address the overall impact of methane on climate change. Ignoring or neglecting these emissions could hinder the progress towards reducing methane and achieving climate goals. Thus, proactive measures are essential to tackle all significant sources of methane emissions, even if they are challenging to measure and manage.

In the past, scientists have commonly measured wildfire emissions by analyzing air samples collected from aircraft, which can be expensive and logistically challenging. However, the UC Riverside research team employed a novel approach to measure emissions from the Sequoia Lightning Fire Complex in the Sierra Nevadas that involved remote sensing. This technique not only provides a safer option for researchers, but also offers the advantage of capturing a more comprehensive plume from the fire that includes various burning phases. This remote sensing method is likely to yield more accurate results, as it provides a holistic and integrated measurement of the emissions from the wildfire. By utilizing innovative techniques like remote sensing, researchers can enhance the accuracy and efficiency of emissions measurements, contributing to a better understanding of the impact of wildfires on methane emissions and climate change.

The remote sensing technique employed by the UC Riverside research team, as detailed in the journal Atmospheric Chemistry and Physics, enabled the lead author, Isis Frausto-Vicencio, a Ph.D. student in environmental sciences at UCR, to safely measure the entire plume of gas and debris emitted by the Sequoia Lightning Fire Complex from a distance of 40 miles. This innovative method allowed for a comprehensive measurement of the emissions without putting researchers in harm's way, making it a safer and more efficient approach. By utilizing remote sensing, researchers were able to obtain valuable data on the emissions from the wildfire, enhancing our understanding of the contribution of wildfires to methane emissions and their impact on the environment.

"The plume, or atmospheric column, is like a mixed signal of the whole fire, capturing the active as well as the smoldering phases," Hopkins said. "That makes these measurements unique."

Rather than using a laser, as some instruments do, this technique uses the sun as a light source. Gases in the plume absorb and then emit the sun's heat energy, allowing insight into the quantity of aerosols as well as carbon and methane that are present.

The remote sensing technique utilized by the researchers revealed a staggering discovery - the Sequoia Lightning Fire Complex emitted nearly 20 gigagrams of methane. To put this into perspective, one gigagram is equivalent to 1,000 metric tons, which is roughly the weight of an elephant. Therefore, the emissions from the fire were equivalent to approximately 20,000 elephants' worth of methane gas. This magnitude of emissions underscores the significant contribution of wildfires to methane emissions and their potential impact on climate change. The use of remote sensing allowed for a more precise measurement of the emissions, providing valuable data to better understand the scale of methane emissions from wildfires and their implications for the environment.

The data obtained from the remote sensing technique used by the UC Riverside researchers aligns with measurements obtained from European Space Agency satellite data, which provides a broader global view of burned areas but is not yet capable of directly measuring methane in these conditions. The use of satellite data offers a valuable tool for monitoring and analyzing large-scale environmental changes, including wildfires. However, when it comes to measuring specific greenhouse gas emissions like methane from wildfires, remote sensing techniques that capture data closer to the source can provide more accurate and detailed measurements. The combination of ground-based remote sensing and satellite data can provide complementary information, offering a more comprehensive understanding of the emissions from wildfires and their impact on global methane levels. Continued advancements in remote sensing technology and satellite capabilities can further enhance our ability to monitor and measure greenhouse gas emissions from wildfires and other sources, contributing to a more informed approach to addressing climate change.

If included in the California Air Resources Board methane budget, wildfires would be a bigger source than residential and commercial buildings, power generation or transportation, but behind agriculture and industry. While 2020 was exceptional in terms of methane emissions, scientists expect more megafire years going forward with climate change.

In 2015, the state first established a target of 40 percent reduction in methane, refrigerants and other air pollutants contributing to global warming by 2030. The following year, in 2016, Gov. Jerry Brown signed SB 1383, codifying those reduction targets into law.

The proposed reductions in methane emissions are aimed at implementing regulations that address various sources of methane, including manure from dairy farms, food waste in landfills, leaks from oil and gas production, and the use of certain gases in refrigerators and air conditioners. These measures are designed to target both anthropogenic and natural sources of methane emissions, with the goal of mitigating the impact of this potent greenhouse gas on climate change. By implementing regulations that capture methane emissions from different sectors and sources, policymakers aim to reduce the overall emissions of methane and achieve cleaner air and climate goals. These efforts highlight the multifaceted approach needed to tackle methane emissions and address their contribution to global warming.

"California has been way ahead on this issue," Hopkins said. 'We're really hoping the state can limit the methane emissions under our control to reduce short-term global warming and its worst effects, despite the extra emissions coming from these fires."

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