Climate Change: Atmospheric Carbon Dioxide

Key Highlights

• Record Levels in 2023: Global average atmospheric CO2 reached 419.3 ppm in 2023, marking a new record.
• Annual Increase: The CO2 concentration increased by 2.8 ppm between 2022 and 2023, continuing a trend over the last 12 years of annual increases exceeding 2 ppm.
• Mauna Loa Observatory: Recorded an annual average of 421.08 ppm in 2023; the highest monthly value recorded was 424 ppm in May 2023.

Factors Contributing to Rising CO2 Levels

• Fossil Fuel Combustion: Carbon from fossil fuels, accumulated over millions of years, is being rapidly returned to the atmosphere.
• Increase in Emissions: Emissions have risen from 11 billion tons per year in the 1960s to an estimated 36.6 billion tons in 2023.

The Carbon Cycle and Natural Sinks

• Natural Sinks: Land and ocean sinks absorb about half of human-emitted CO2 each year.
• Overshoot: Human emissions exceed the capacity of natural sinks, leading to a net increase in atmospheric CO2.

Historical Context

• Rapid Increase: From 0.8 ppm per year in the 1960s to 2.4 ppm per year in the 2010s.
• Comparison to Natural Increases: Current rates of increase are about 100 times faster than natural post-ice age increases.

Impact of Carbon Dioxide

• Greenhouse Effect: CO2 is a critical greenhouse gas, responsible for about two-thirds of human-induced warming.
• Ocean Acidification: CO2 dissolves in ocean waters, forming carbonic acid, and has led to a drop in ocean pH from 8.21 to 8.10 since the Industrial Revolution.

Historical CO2 Levels

• Ice Core Data: Over the last million years, CO2 never exceeded 300 ppm until recent industrial activities.
• Comparison to Past: Current levels are higher than at any time in human history, comparable to conditions 3 million years ago.

Future Projections

• Socioeconomic Pathways: If fossil fuel use continues unabated, CO2 levels could reach 800 ppm by the end of the century.
• Potential Consequences: Such levels could lead to conditions not seen for 50 million years, with significantly higher global temperatures and sea levels.

Additional Resources

• NOAA Observations: A resource for ongoing CO2 monitoring.
• Carbon Cycle Factsheet: Information on how carbon cycles through the environment.
• Emission Trends by Country: Understanding regional contributions to global CO2 emissions.

Conclusion

Carbon dioxide is a key driver of climate change due to its role in the greenhouse effect and ocean acidification. The rapid increase in atmospheric CO2 levels is primarily driven by human activities, particularly the burning of fossil fuels. The continuation of current emission trends could lead to significant and potentially irreversible changes in Earth's climate system.