This claim is true. The world's leading scientific institutions — including the IPCC, NASA, NOAA, and the National Academies — independently confirm that human greenhouse gas emissions are the primary driver of observed warming since the mid-20th century. Quantitative attribution studies show human activity caused approximately 1.07°C of warming, while natural factors (solar, volcanic) contributed only –0.1°C to +0.1°C. A small number of low-authority dissenting sources exist but provide no peer-reviewed evidence that overturns this conclusion.