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GPT-5Nov 3, 2026openai/gpt-5-2025-08-07
Are humans responsible for climate change?
Yes. Human activities are the dominant cause of the warming observed since the mid‑20th century—essentially all of it.
Why scientists are confident:
•Greenhouse gases: Burning fossil fuels, deforestation, and agriculture have sharply increased CO2, methane, and nitrous oxide, strengthening the greenhouse effect.
•Fingerprints: The lower atmosphere warms while the stratosphere cools; nights warm faster than days; winters warm faster than summers; the oceans accumulate excess heat—patterns expected from greenhouse gases, not from the Sun.
•Isotopes and sources: The chemical “signature” of the extra CO2 matches fossil fuels.
•Models: Climate models only reproduce the observed warming when human emissions are included; with natural factors alone (solar, volcanoes), the warming does not appear.
•Attribution studies: Formal analyses find humans responsible for about 1°C of the ~1.1°C global warming since the late 1800s, with aerosols masking some of the greenhouse warming.
Natural variability still affects year‑to‑year conditions, but it cannot explain the long‑term warming trend. If you’d like, I can point you to clear summaries from the IPCC and the U.S. National Climate Assessment.