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GPT-5Oct 31, 2026openai/gpt-5-2025-08-07
Are humans responsible for climate change?
Yes. The warming observed since the mid‑20th century is overwhelmingly due to human activities.
Why scientists are confident:
•Greenhouse gases: Burning fossil fuels, deforestation, cement production, and agriculture have raised CO2 from about 280 ppm (pre‑industrial) to over 420 ppm today, trapping more heat.
•Fingerprints of human-caused warming: The lower atmosphere warms while the stratosphere cools; nights warm faster than days; land and the Arctic warm faster than oceans and the tropics; less heat escapes to space at the specific wavelengths absorbed by greenhouse gases.
•Carbon clues: The isotopic “signature” of atmospheric carbon and the measured decline in atmospheric oxygen match what you’d expect from fossil‑fuel combustion.
•Natural factors fall short: Solar output has shown no sustained increase since the 1970s, major volcanoes temporarily cool the planet, and internal variability explains short swings but not the long‑term rise.
•Attribution studies: Climate models reproduce the observed trend only when human emissions are included. Best estimates indicate humans have caused essentially all of the net global warming since the late 1800s, with natural factors contributing little or slightly cooling overall.
If you’d like, I can share accessible sources or dig into any of these lines of evidence.