Glaciergate
The 2035 disappearing glaciers claim was one of those "OMG this stuff is serious!" moments that nearly had me convinced. And when an Indian government report queried it, the head of the IPCC called them "climate change deniers and school boy science". Turns out the boot was on the other foot. More science and less alarmism would be nice but nobody trusts anybugger anymore, I expect to be disappointed.