Of course the increase in rat numbers in cities is caused by climate change. As the ice melts due to the seething heat caused by global warming, the melted ice-water from the arctic chills the air throughout the entire planet and so the rats get cold and they have to move closer to the cities to warm up on the hot bitumen. Also, they have to huddle up together to stay warm and thus they breed more.

The heat causes cooling which creates a feedback cycle thus releasing more heat which melts everything which causes yet more cooling. This makes sense. The science is settled. Trust the science.