What layer lies directly above the troposphere and is warmer at the top than at the bottom?

The layer that lies directly above the troposphere and is characterized by an increase in temperature with altitude is the stratosphere. In this layer, the temperature rises as one moves higher up, primarily due to the presence of the ozone layer, which absorbs and scatters ultraviolet solar radiation. This absorption of energy warms the upper portions of the stratosphere more than the lower portions.

In contrast, the troposphere, which is the layer beneath the stratosphere, generally experiences a decrease in temperature with height. This characteristic temperature gradient is primarily due to the proximity to the Earth's surface, where the heat is generated.

The mesosphere, which lies above the stratosphere, exhibits a decrease in temperature with altitude, while the exosphere, the outermost layer of the atmosphere, is where temperatures can vary widely but is not defined by the same temperature structure as the stratosphere and troposphere. Thus, understanding these thermal characteristics helps clarify why the stratosphere is the correct answer.