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GPT-5Oct 8, 2026openai/gpt-5-2025-08-07
Are humans responsible for climate change?
Yes—overwhelmingly. The warming observed since the late 1800s (about 1.1°C globally) is effectively entirely due to human activities, chiefly burning coal, oil, and gas, plus deforestation and certain industrial/agricultural practices.
How we know
•Greenhouse gases spiked: CO2 rose from ~280 ppm pre‑industrial to over 420 ppm today, with carbon‑isotope fingerprints and a small decline in atmospheric O2 showing the increase comes from fossil fuels.
•Physical “fingerprints”: the lower atmosphere (troposphere) warms while the stratosphere cools; land warms faster than ocean; the Arctic warms fastest; nights warm faster than days—patterns expected from greenhouse gases, not from the Sun.
•Energy measurements: satellites and surface instruments detect more downward longwave radiation at CO2/CH4 wavelengths and less heat escaping to space; the oceans (which store >90% of excess heat) show a sustained rise in heat content.
•Attribution studies: climate models only match the observed trend when human greenhouse gases and aerosols are included; natural drivers (solar changes, volcanoes, internal variability) alone cannot reproduce the warming and have been roughly neutral to slightly cooling over recent decades.
If you’d like, I can share key sources or dive deeper into any of these lines of evidence.