Whether climate change is happening or not...
I have issues with the IPCC data and its lack of transparency. They are the sole arbiters of the accumulated historical climate data - which in itself is a bit whiffy.
The 'hockey stick' of the temperature rise originally presented ... Back in the late 80's I think ... was shown to have been based on some dubious statistical practise and they were called out on it (by a very few) so they went away, massaged the figures some more, and then represented the same 'hockey stick' graph of temperature rise.
The mass of data (it is a very large amount!) is held by them, they release sets of this data, to anyone interested, but they don't allow release of the (even bigger mass) original prinary source data - as far as I can recall.
It's only in the last 50 or so years , that we have comprehensive data capturing for the entire globe.
As I said, I'm not saying whether global warming is happening or not.
Just... That for something as important as it potentially is, to mess up the science and maths, is a serious mistake for legitimacy and transparency.