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GPT-5Oct 23, 2026openai/gpt-5-2025-08-07
Are humans responsible for climate change?
Yes. The warming observed over the past century is overwhelmingly driven by human activities—chiefly burning fossil fuels, deforestation, and certain agricultural/industrial practices that increase heat‑trapping gases like CO2, methane, and nitrous oxide.
Why scientists are confident:
•Fingerprints in the air: The extra CO2 has the isotopic “signature” of fossil fuels (lower 13C/12C) and is accompanied by declining atmospheric oxygen—exactly what combustion predicts.
•Energy imbalance: Satellites and ocean measurements show Earth taking in more energy than it loses; over 90% of that excess heat is accumulating in the oceans.
•Vertical and regional patterns: The lower atmosphere (troposphere) is warming while the stratosphere cools; nights and winters warm faster than days and summers; the Arctic warms fastest. These patterns match greenhouse‑gas forcing, not solar changes.
•Natural drivers don’t fit: Solar output and volcanic activity can’t explain the magnitude or pattern of recent warming; without human emissions, models indicate little warming or even slight cooling over recent decades.
•Models and observations agree: Climate models that include human greenhouse gases reproduce the timing and amount of observed warming; models with only natural factors do not.
•Multiple lines of evidence: Rising sea level (from thermal expansion and melting ice), retreating glaciers, earlier spring onset, and shifting ecosystems all cohere with a warming world driven by greenhouse gases.
Bottom line:
•Human influence is the dominant cause of global warming since the mid‑20th century; best estimates attribute essentially all of the net warming to human activities, with natural factors contributing little on balance.