The empirical evidence is irrefutable, no longer debatable.
These 20 studies confirm that the known Northern Hemisphere natural climate change periods, referred to as the Little Ice Age, the Medieval Warming, the Dark Ages and the Roman Period, also had significant impacts on the Southern Hemisphere.
In all cases, across both hemispheres, the large, natural climate changes took place without any human CO2 influence.
This means that natural climate change is caused by other factors that are of either earthly or (and) cosmic/solar origins.