Final answer:
The warmest point in the troposphere, the lowest layer of the atmosphere, is at its bottom, near the Earth's surface, because the surface absorbs sunlight and heats the air directly above it.
Step-by-step explanation:
The troposphere is the lowest layer of Earth's atmosphere. It extends from the Earth's surface up to about 11-13 km (7-8 miles), although this can vary depending on the geographic location, being thicker at the equator and thinner at the poles. The temperature of the troposphere is warmest at the bottom, near the Earth's surface, because the surface absorbs sunlight and warms the air above it through conduction and convection. As you go higher in the troposphere, both air density and temperature decrease. This is why the temperature of the troposphere is described as decreasing steadily with increasing altitude. The warmest point in the troposphere is therefore at its lowest point, right at the Earth's surface.