Final answer:
The increase in temperature causing an increase in ice cream sales exemplifies a causation rather than a mere correlation, as warmer weather directly increases the demand for cold treats.
Step-by-step explanation:
The situation that represents causation rather than correlation is the increase in temperature and the increase in ice cream sales. This is because a rise in temperature is a direct cause of people's desire to cool down, which often involves consuming cold treats like ice cream.
Correlation does not imply causation, meaning that just because two variables change in tandem, it does not indicate that one causes the other to change. In the other examples given, the increases observed in sales of sunglasses, police presence, and umbrellas may not be direct results of the initial increases noted, and could be attributed to other factors, known as confounding variables, that cause systematic movement in our variables of interest. For instance, an increase in ice cream sales and in sunglasses sales may both be due to the increase in outdoor activities during the summer rather than sunglasses sales causing ice cream sales or vice versa.
In contrast, a direct causal relationship is evident between the rise in temperature and the increase in ice cream sales: warmer temperatures lead directly to a higher demand for cold refreshments. This is an example of positive correlation, where the increase in one variable directly leads to the increase in the other variable.