Dramatic Lockdown Fossil Fuel CO₂ Decrease Detected by Citizen Science-Supported Atmospheric Radiocarbon Observations

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Climate Science

Background:

• COVID-19 lockdowns drastically altered global fossil fuel CO2 emissions, particularly from transportation.
• Travel restrictions during lockdowns impeded traditional methods for monitoring emission changes in real-time.

Purpose of the Study:

• To utilize a citizen science approach to measure localized fossil fuel CO2 emission changes during COVID-19 lockdowns.
• To engage young people in climate science through hands-on data collection and analysis.
• To compare emission changes during lockdown periods with non-lockdown periods.

Main Methods:

• A citizen science campaign was implemented where participants collected grass samples.
• Radiocarbon content analysis of grass samples was performed to determine atmospheric fossil fuel CO2 mole fraction.
• Local fossil fuel CO2 mole fractions during lockdown were compared to baseline non-lockdown data.

Main Results:

• Seventeen sampling sites across five New Zealand cities showed an average reduction in traffic emissions of 75 ± 3% during the strictest lockdown phase.
• These findings align with limited traffic count data and indicate a more substantial decrease than global estimates.
• Emission reductions varied geographically, with urban centers, especially those with significant bus traffic, exhibiting smaller decreases.

Conclusions:

• Citizen science, using radiocarbon analysis of grass, provides a viable method for monitoring localized CO2 emissions during periods of restricted activity.
• COVID-19 lockdowns led to significant, location-specific reductions in traffic-related fossil fuel CO2 emissions in New Zealand.
• Localized emission patterns differed, influenced by factors such as the type of traffic (e.g., bus dominance in city centers).