I appreciate having a link to a known pseudo science resource, but that article is referencing non-anthropogenic climate change - specifically that there are relatively mild temperature cycles measured in the spans of hundreds of years. Dropping a couple of degrees would (and in relatively recent history has) significantly impacted crop failure rates.

However that is kind of moot, because human driven climate change has been pushing temperatures up faster than any natural temperature reduction has ever achieved. Even if we would otherwise be experience a reduction in average global temperature it doesn't matter because human driven warming would overcome that.