Climate would be only one of hundreds of factors. Some factors are more important than others, depending on the historical era. Absolute, science-centered modernity reset the stage for progress, which is why it's stranger now that the hotter regions aren't excelling as well as the cooler ones. In the ancient past, stagnant conservatism was the societal default, whereas progressive liberalism became the modern default, so climate now may be a greater factor in explaining the global divide.