He did it after he got his aerosol optical physics wrong. (judithcurry.com)
So, the climate scam has for 50 years been based on a fundamental mistake in aerosol optical physics. (notrickszone.com)
``... when you correct Sagan's incorrect optical physics of sols, which started the whole CAGW scare, «cloud albedo effect» cooling changes to heating, another AGW which is self - limiting.» (realclimate.org)