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GPT-5Sep 15, 2026openai/gpt-5-2025-08-07
Are humans responsible for climate change?
Yes
Yes. Human activities are the primary cause of the rapid warming observed since the mid‑20th century.
Why scientists are confident:
•Greenhouse gases from burning fossil fuels, deforestation, and industry have raised CO2 from about 280 ppm pre‑industrial to over 420 ppm today, strengthening the greenhouse effect.
•The added CO2 has a fossil‑fuel “fingerprint” (isotopes and concurrent drop in atmospheric O2) that matches combustion.
•The observed warming pattern fits greenhouse forcing: the lower atmosphere and surface warm while the stratosphere cools; nights warm faster than days; the oceans accumulate most of the excess heat; the Arctic warms fastest.
•Climate models reproduce recent warming only when human emissions are included; natural factors alone (solar and volcanoes) cannot explain it and would have caused little warming or slight cooling over this period.
In short, humans are responsible for essentially all of the net global warming since the mid‑1900s.