Fact check: What is the current concentration of CO2 in the Earth's atmosphere?

1. Summary of the results

Based on the available data, the current concentration of CO2 in Earth's atmosphere is approximately 426.40 parts per million (ppm) as of March 2025 ^[1]. This represents a significant increase from the 2024 global average of 422.8 ppm reported by climate.gov ^[2] and the 422.5 ppm figure cited by the International Energy Agency ^[3].

The NOAA Global Monitoring Laboratory provides the most recent and relevant data for answering this question, offering monthly measurements that show the atmospheric CO2 concentration has continued its upward trajectory into 2025 ^[1]. This increase aligns with the trend of rising emissions, as the IEA reported that CO2 emissions increased by 0.8% in 2024, reaching record high levels ^[3].

2. Missing context/alternative viewpoints

The original question, while straightforward, lacks important contextual information that would help understand the significance of current CO2 levels:

• Historical perspective: None of the sources provide pre-industrial baseline measurements (typically around 280 ppm) to show how dramatically current levels exceed natural historical ranges
• Seasonal variations: The March 2025 measurement ^[1] doesn't account for natural seasonal fluctuations in CO2 levels, which typically peak in late spring in the Northern Hemisphere
• Regional variations: The sources focus on global averages but don't address how CO2 concentrations vary geographically
• Rate of change: While the data shows an increase from 2024 to 2025, the sources don't provide detailed information about whether this rate of increase is accelerating or consistent with recent trends
• Measurement methodology: The sources don't explain how these measurements are collected or the precision of the monitoring systems

3. Potential misinformation/bias in the original statement

The original question itself contains no apparent misinformation or bias - it is a straightforward factual inquiry about current atmospheric CO2 concentrations. However, there are some considerations:

• The question asks for "current" concentration without specifying a timeframe, which could lead to confusion given that CO2 levels fluctuate monthly and seasonally
• Different organizations may report slightly different values due to varying measurement methodologies, as evidenced by the small discrepancies between the 2024 figures from climate.gov (422.8 ppm) and the IEA (422.5 ppm) ^{[2] [3]}
• The question doesn't acknowledge that CO2 concentrations are constantly changing, which might imply to some readers that there is a single, static answer

The sources themselves appear to be from reputable scientific organizations (NOAA, climate.gov, and IEA), suggesting minimal bias in the underlying data, though each organization may have different measurement protocols or reporting schedules.