If official, peer-reviewed reports from international agencies are "wrong or lying," what better sources would you recommend?
Or more importantly..
If they're wrong, why aren't any of the groups involved catching these errors and correcting them?
If they're lying, you're suggesting a multi-decade, international conspiracy spanning thousands of people that threatens humanity as a whole where the watchdogs are either complicit or not competent enough to catch. I hope you have something to back that up.
This doesn't require some complex conspiracy, just some natural amount of wanting to tell people (heads of state) what they want to hear, some amount of funding and promoting less alarmist research, some amount of feeling like they have a duty to avoid extreme rhetoric etc.
I hope it's clear, I'm not claiming that I know all this for a fact. But it is how international organizations seem to operate in general. You would definitely not expect a major international inter-governmental organization to present a position that would be called extreme position, even if that extreme position may be right.
So yes, most likely the IPCC is wrong or lying to some extent: global warming is almost certainly a much bigger problem than their official estimates.