Good point - I should have included human-generated CO2 driven climate change. (That is what the watermelons always infer with climate change, not natural transition or variation.)
As for population genetics and selection pressure, I am familiar with this topic. Selection pressure changes the frequency of alleles in the population. These alleles are all part of the species’ gene pool. It is hardly evolution. It, in no way, contributes to speciation.
You are not saying that small temperature changes or atmospheric humidity increases increase mutation frequency, are you?
Sickle cell anemia is a classic example of a mutation that changes frequency based on environment/selection pressure - it is beneficial in fighting malaria. - But Malaria did not cause the sickle cell allele to come into being. That thought is Lamarkian.
There is constant climate change without any consideration of human caused CO2. Climate is not static and has so many different influencing factors that models have so far failed. Ice columns drilled in Greenland give us a record of constant climate change over hundreds of thousands years.
Evolution is a fact, deal with it.