Limits RegistryPUBLIC RECORD
Limits RegistryGlobal atmospheric CO₂ concentration has exceeded 420 ppm in the modern instrumental record and continues to vary with season and year.
The question, scope, and sources behind this Registry record.
Global atmospheric CO₂ concentration has exceeded 420 ppm in the modern instrumental record and continues to vary with season and year.
Track the maximum globally representative atmospheric CO₂ concentration for a stated averaging window and year.
Atmospheric CO₂ is a time-indexed global measurement assembled from monitoring stations and atmospheric transport methods. A useful registry record must preserve the observation year, averaging method, and whether the value is monthly, annual, or daily.
National Centers for Environmental Information — Atmospheric carbon-dioxide concentration frontierChange a parameter to stress-test whether a proposed result is still inside the published specification. This is an audit aid, not a proof checker.
Current frontiers derived from accepted Claims.
The frontier is not sacred
Most progress starts with a disagreement that survives contact with evidence. If you can push the known lower bound up or pull the upper bound down, show us the work.
≥ when you have shown that at least this value is achievable.≤ when you have shown that anything above this value is impossible.No vibes. State the value, define the scope, and link the paper, proof, code, or reproduction that lets another person check it. Editors review every challenge before the public record changes.
Challenge this recordAssertions tied to evidence, attribution, and review.
The frontier as it changed over time.
Only accepted Claims matching the current specification contribute to the displayed bounds. Strict inequalities remain open; contradictory Claims require editorial review.
Permanent ID limitsregistry.com/limits/LR-004213
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Limits Registry. LR-004213. Atmospheric carbon-dioxide concentration frontier. 2026.