Answer:
decreasing with latitude
Explanation:
The sunlight is the primary heat source of Earth. The sunlight though doesn't fall at the same angle everywhere on Earth, thus it is not warming up equally every part of Earth.
The reason for this is that Earth, as the other plants, has rounded shape, or rather an elliptical shape. Because of the shape of Earth, the sunlight falls at highest angles around its central part, the tropics. As we move away from the tropics though, and as the planets curvature increases, the sunlight falls at lower and lower angles, thus the angle by which the sunlight falls is decreasing as the latitude is increasing.
The end result of this is that the lower latitudes are the warmest because the sunlight is more concentrated, the mid-latitudes are temperature because the angle of the sunlight is smaller, while the high latitudes are very cold because the sunlight falls at very small angles so they are dispersed over very large area.
