variation and change are assigned significance by biased humans.  models are created to guide our interpretation of data.  these models are supremely weak. 

i think you'd be surprised at 1) how small the scientific community is 2) how much weight "in my expert opinion" carries 3) how much government money, with strings attached, has been poured into climate study infrastructure and model construction--profoundly influencing scientist's interpretation of data

and all data is manufactured.  it's physical phenomena transformed into numbers on a page.  the whole process of how those numbers are created is rife with bias and error.  in this area of climate, the relationship between {number and location of sensors} and {model detail} is the key to understanding how bogus this shit is.

source:  analytical chemist's (phd + industry) expert opinion

1 climate variation: no duh
2 regional climate trends over time: depends
3 global climate trend over time: unknown
4 significance of regional climate trends over time: depends
5 significance of global climate trend over time: can't answer without #3