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GPT-5Sep 6, 2026openai/gpt-5-2025-08-07
Are humans responsible for climate change?
Yes
Yes. The overwhelming scientific consensus is that humans are the primary cause of the global warming observed since the mid‑20th century.
Why scientists are confident:
•Greenhouse gases from human activities have surged: CO2 has risen from ~280 ppm pre‑industrial to over 420 ppm today, with methane and nitrous oxide also sharply up. These gases trap heat.
•Energy balance: The best estimate of net human-caused radiative forcing is about +2.7 W/m² since 1750, while natural factors (solar, volcanoes) explain little of the recent long‑term warming.
•Fingerprints of greenhouse warming:
•Troposphere warms while the stratosphere cools.
•Nights and winters warm faster than days and summers.
•The Arctic warms faster than the global average.
•Oceans accumulate the vast majority of excess heat.
•CO2’s isotopic and O2 signatures match fossil fuel combustion.
•Models and observations: Only simulations that include human emissions reproduce the observed warming trend; runs with natural factors alone do not.
•Context: Current CO2 levels are the highest in at least 2 million years, and the rate of warming exceeds natural variability over at least the last 2,000 years.
Authoritative assessments (IPCC AR6, U.S. National Academies, NASA/NOAA, WMO) conclude it is unequivocal that human influence has warmed the atmosphere, ocean, and land, and that essentially all of the observed global surface warming since the late 19th century is due to human activities, with natural factors contributing little to the long‑term trend.
If you’d like, I can summarize the key evidence in more detail or point you to primary sources.