the 40-day rain itself was more of an anomaly than a long-term weather pattern, so i wouldn't say it could count as climate change. but the entire earth being flooded for well over a year is definitely not something to ignore-- i find it very hard to believe that the earth's surface being raised way up in altitude and almost entirely consisting of water wouldn't have any effect on the worldwide climate after several months
i think his whole point is that from a religious view, climate change is not something that can be dismissed by christians as "not real" bc it's basically right in the bible, and that's why he doesn't doubt its existence