CO2 Concentration in Atmosphere
CURRENT TOTAL
Live Counter Notable Facts
(Measured at Mauna Loa Observatory, Hawaii)
Current Concentration
Annual Increase
Above Pre-industrial
Understanding CO2 Concentration in Atmosphere
This counter tracks the concentration of carbon dioxide in Earth's atmosphere, measured in parts per million (ppm). Atmospheric CO2 is the primary driver of global warming, with current levels the highest in over 3 million years of Earth's history.
In 2025, atmospheric CO2 reached 426.6 ppm annual average, with seasonal peaks approaching 430 ppm. This represents a 52% increase from pre-industrial levels of 280 ppm and continues to rise at an accelerating rate due to ongoing fossil fuel emissions and reduced natural carbon absorption.
The rate of CO2 accumulation is unprecedented, increasing 100 times faster than natural variations at the end of ice ages. In 2024, CO2 rose by 3.58 ppm, the largest annual increase ever recorded, driven by record fossil fuel emissions and weakened carbon sinks from drought and wildfires.
Atmospheric CO2 Trends and Impacts
- The last time atmospheric CO2 exceeded 400 ppm was during the Pliocene epoch 3-5 million years ago, when global temperatures were 2-3°C warmer, ice sheets were significantly smaller, and sea levels were 15-25 meters higher than today. Current CO2 levels are committing Earth to similar long-term changes.
- CO2 remains in the atmosphere for centuries, with 20-40% of emissions staying airborne for over 1,000 years. This means current emissions will affect climate for millennia, making rapid reductions essential to limit peak warming and avoid triggering irreversible tipping points in the climate system.
- Natural carbon sinks in oceans and forests currently absorb about 50% of human CO2 emissions, but this fraction is declining as sinks weaken. Ocean acidification from CO2 absorption has already lowered ocean pH by 0.1 units (30% increase in acidity), threatening marine ecosystems and food chains.
- To stabilize atmospheric CO2 and limit warming to 1.5°C requires reducing emissions by 50% by 2030 and reaching net zero by 2050. Current emission trends would push CO2 past 500 ppm by 2050, locking in catastrophic warming of 3°C or more.
CO2 Measurement Terms
- Parts Per Million (ppm): Number of CO2 molecules per million molecules of dry air
- Keeling Curve: Graph showing continuous CO2 measurements since 1958 at Mauna Loa
- Carbon Sinks: Natural systems (forests, oceans) that absorb CO2 from the atmosphere
- Airborne Fraction: Percentage of emitted CO2 remaining in atmosphere (~45-50%)
Historical CO2 Levels
- Pre-industrial (1850): 280 ppm
- Start of measurements (1958): 315 ppm
- Crossed 350 ppm: 1988
- Crossed 400 ppm: 2013
- Current (2025): 426.6 ppm
CO2 Growth Rates by Decade
- 1960s: 0.9 ppm/year
- 1980s: 1.6 ppm/year
- 2000s: 2.0 ppm/year
- 2010s: 2.4 ppm/year
- 2020s (so far): 2.8 ppm/year
Future CO2 Scenarios
- May 2025 peak: 429.6 ppm (highest in 2+ million years)
- 2030 (current trend): 440-445 ppm
- 2050 (current policies): 500-520 ppm
- 2100 (high emissions): 800-1000 ppm
- Safe limit for 1.5°C: ~430 ppm peak
Data Sources and References
Methodology and Data Collection
Atmospheric CO2 concentrations are measured continuously at Mauna Loa Observatory in Hawaii and other global monitoring stations, providing the longest continuous record of atmospheric CO2 levels since 1958.
The counter tracks real-time CO2 levels based on current measurements and seasonal patterns, showing the accelerating accumulation of greenhouse gases in Earth's atmosphere.
Frequently Asked QuestionsAbout CO2 Concentration in Atmosphere
CO2 is measured continuously at Mauna Loa Observatory and 100+ global stations using precise infrared analyzers. The Keeling Curve (since 1958) is the longest continuous atmospheric record. Current 426.6 ppm average is measured to 0.1 ppm accuracy.
Data comes from NOAA Global Monitoring Laboratory, Scripps Institution's Keeling Curve, Global Carbon Project, and World Meteorological Organization Greenhouse Gas Bulletin - the authoritative sources for atmospheric composition monitoring.
The last time CO2 exceeded 400 ppm was 3-5 million years ago when temperatures were 2-3°C warmer and sea levels were 15-25 meters higher. CO2 is accumulating 100 times faster than natural variations. The 3.58 ppm increase in 2024 was the largest ever recorded.
CO2 traps heat in the atmosphere, driving global warming. A 52% increase from 280 to 426 ppm has already caused 1.2°C warming. CO2 stays in the atmosphere for centuries - 20-40% persists for over 1,000 years - making rapid emission reductions essential.
Pre-industrial levels were 280 ppm. Scientists estimate staying below ~430 ppm gives a chance to limit warming to 1.5°C. At current trends, we'll hit 500 ppm by 2050, locking in 3°C+ warming. Net zero emissions by 2050 is required to stabilize levels.