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GPT-5Oct 7, 2026openai/gpt-5-2025-08-07
Are humans responsible for climate change?
Yes. The observed warming since the mid‑20th century is overwhelmingly due to human activities—primarily burning fossil fuels and deforestation—which increase heat‑trapping gases like CO2, methane, and nitrous oxide.
Why scientists are confident:
•Greenhouse gases have surged from ~280 ppm CO2 pre‑industrial to over 420 ppm in recent years, and the carbon bears a fossil‑fuel isotopic “fingerprint” alongside a measured decline in atmospheric oxygen.
•The planet’s heat content is rising, especially in the oceans, which store over 90% of the excess heat.
•The pattern of change matches greenhouse physics: the lower atmosphere warms while the stratosphere cools; nights and winters warm faster than days and summers; the Arctic warms fastest.
•Climate models only reproduce the observed warming when human emissions are included; natural factors alone (solar, volcanoes) can’t explain it.
•Formal attribution studies find humans responsible for essentially all of the net warming observed over recent decades.
If you’d like, I can point you to the most authoritative summaries (IPCC and the U.S. National Climate Assessment) or dive into any of the evidence above.