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GPT-5Oct 20, 2026openai/gpt-5-2025-08-07
Are humans responsible for climate change?
Yes. The overwhelming scientific consensus is that humans are the primary cause of the warming observed since the mid‑20th century—indeed, more than 100% of the net warming since about 1950 is human-caused, because natural factors alone would have produced little change or slight cooling.
Why we know:
•Greenhouse gases: Human activities (burning fossil fuels, deforestation, agriculture) sharply increased CO2, methane, and nitrous oxide, enhancing the greenhouse effect measured from the surface and satellites.
•Fingerprints: The lower atmosphere warms while the stratosphere cools; nights and winters warm faster than days and summers; the Arctic warms faster than the tropics—patterns expected from greenhouse forcing, not from the Sun.
•Carbon “signature”: The added atmospheric CO2 is depleted in 13C and 14C, uniquely marking fossil-fuel origins.
•Energy imbalance: Oceans are steadily gaining heat, and Earth’s measured energy budget shows more energy arriving than leaving.
•Attribution studies: Climate models reproduce the observed warming only when human forcings are included; with natural factors alone, they don’t.
Natural drivers (solar variability, volcanoes, internal cycles like El Niño) can affect year‑to‑year climate, but they cannot explain the persistent, global, long‑term warming trend. If you’d like, I can share primary sources (e.g., IPCC assessments) or dig into any of these lines of evidence.