"The weather is different now than it was 30 years ago" is definitely something that can be judged with some level of confidence by a 40 year old, despite their

"The weather is different now than it was 30 years ago" is definitely something that can be judged with some level of confidence by a 40 year old, despite their possible cognitive biases that could confound this judgment. Saying "they can't tell how the weather is changing on a 20,000 year timescale" isn't relevant to that claim.