It's not today's weather that gives them that, it's the lifetime of weather experience. If you're talking to someone at least 40 years old then it meets the 3 conditions.
If they were like 20,000 years old, they might have some wisdom after going through natural ice ages and other cyclical patterns that take more than several lifetimes to go through. 40 years? When talking about a planet billions of years old with long hot/cold stretches lasting thousands of years each? Polar shifts? I'd wager they don't have enough data gathered during their insignificant blip of a lifetime to make speculative global warming claims.