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GPT-5Nov 2, 2026openai/gpt-5-2025-08-07
Are humans responsible for climate change?
Yes. The warming observed over the past century is overwhelmingly driven by human activities—mainly burning fossil fuels, deforestation, and some industrial/agricultural practices.
Key evidence in brief:
•Greenhouse gases have surged: CO2 rose from ~280 ppm (pre‑industrial) to over 420 ppm today. Its isotopic “fingerprint” and a measured drop in atmospheric O2 show the added CO2 comes largely from fossil fuels.
•Distinct “fingerprints” of human-caused warming match observations: the lower atmosphere warms while the stratosphere cools; nights warm faster than days; land warms more than ocean; the Arctic warms fastest.
•Models only reproduce the observed warming trend when human emissions are included; natural drivers (solar changes, volcanoes, internal variability) can’t explain the long‑term rise since the mid‑20th century.
•Earth’s energy imbalance is measured directly, mainly as rising ocean heat content, confirming more heat is being trapped.
•Best estimates find humans are responsible for essentially all of the net warming since 1950 (natural factors were small or slightly cooling), with global temperatures now roughly 1.2°C above pre‑industrial levels.
If you’d like, I can point you to plain‑language summaries or dive deeper into any of these lines of evidence.