The last sentence of the abstract should grab any thinking person. And this is from 1990.
Coherence established between atmospheric carbon dioxide and global temperature
Craig Lindberg &
David J. Thomson
Nature volume 343, pages 709–714, 1990
The hypothesis that the increase in atmospheric carbon dioxide is related to observable changes in the climate is tested using modern methods of time-series analysis. The results confirm that average global temperature is increasing, and that temperature and atmospheric carbon dioxide are significantly correlated over the past thirty years. Changes in carbon dioxide content lag those in temperature by five months.