100-200 years is pretty fast when compared to how slowly climate moves in one direction or the other. Also those 100-200 years are the same in which human instrialization took place. Measuring temperature in a global scale is a very daunting task and it is open to interpretations by negationists and reactionaries, but you can look for pictures of the last 30 years in the North Pole. The Arctic is going to be open to navigation soon. You can also ask the climate experts, we have to rely on them, and the vast majority of them are predicting a similar effect.