Global Warming and Temperature Changes in the Atmosphere

Global warming refers to the long-term heating of Earth's climate system observed since the pre-industrial period (between 1850 and 1900) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere.

How Greenhouse Gases Affect Atmospheric Temperature

Greenhouse gases, such as carbon dioxide (CO\(_2\)), methane (CH\(_4\)), and nitrous oxide (N\(_2\)O), trap heat radiated from the Earth's surface. This trapped heat warms the lower layers of the atmosphere.

Identifying the Atmospheric Layer Affected by Warming

The Earth's atmosphere is divided into several layers based on temperature profiles:

• Troposphere: This is the lowest layer, extending from the Earth's surface up to about 7-15 km. It contains most of the atmosphere's mass and is where weather occurs. Greenhouse gases accumulate primarily in this layer and near the surface, effectively trapping heat close to the ground.
• Stratosphere: Located above the troposphere, extending up to about 50 km. It contains the ozone layer, which absorbs ultraviolet (UV) radiation from the sun, causing temperature to increase with altitude in this layer. Global warming leads to less heat escaping from the troposphere to the stratosphere, and ozone depletion also contributes to cooling in parts of the stratosphere.
• Mesosphere: Above the stratosphere, up to about 85 km. Temperature decreases with altitude here. Changes in lower layers can affect the mesosphere, often leading to cooling.
• Ionosphere (Thermosphere): Above the mesosphere, where gases are ionized by solar radiation. This layer extends hundreds of kilometers. It is less directly affected by the trapping of heat near the Earth's surface compared to the lower layers.

The primary effect of increased greenhouse gases is the trapping of heat in the lowest part of the atmosphere, which is the troposphere. As more heat is trapped, the temperature of the troposphere increases. This is the core manifestation of global warming.

Therefore, in global warming, the temperature of the troposphere increases.