Which molecules are considered greenhouse gases? The absorption of infrared radiation depends on molecular structure. Symmetrical diatomic molecules such as O₂ and N₂ absorb very weakly in the thermal infrared range (roughly 4 to 40 μm, corresponding to much of the Earth’s infrared emission spectrum). By contrast, triatomic or non-symmetrical molecules such as H₂O, CO₂, […]
The Earth’s radiation budget can be analysed both at the top of the atmosphere and at the surface (Figure 2.7). At the top of the atmosphere, the long-term equilibrium condition is that absorbed solar radiation must balance outgoing radiation to space. However, under present-day conditions, this balance is slightly positive: the Earth system currently absorbs […]
Recall that all matter with a temperature above absolute zero emits electromagnetic radiation, and that the intensity of this radiation increases with temperature. To understand the effect of greenhouse gases in the atmosphere, two main parameters must be considered at any given altitude: These two parameters determine the intensity of infrared radiation emitted to space […]
Incoming solar radiation Solar radiation reaches the Earth after passing through the atmosphere. Because of the Sun’s high surface temperature, this radiation is concentrated at short wavelengths, mainly from the ultraviolet (UV) to the near-infrared range. The red curve (Figure 1) represents the radiation emitted by the Sun approximated as blackbody radiation. In physics, a […]
How is heat transferred? There are three main modes of heat transfer: In space, which is essentially a vacuum, heat can only be transferred through radiation. Any body with a temperature above absolute zero (0 K = −273.15 °C) emits electromagnetic radiation as a result of the thermal agitation of its particles. The characteristics of […]
Any body with a temperature above absolute zero emits electromagnetic radiation. This radiation spans a range of wavelengths, the distribution of which depends on the surface temperature of the emitting body. This relationship is described by Planck’s law, which defines the spectral distribution of radiation emitted by a black body as a function of wavelength […]
The atmosphere is the gaseous envelope surrounding the Earth. Its composition is generally described in terms of dry air, since water vapor (H₂O), which typically ranges from about 1% to 5% by volume, is highly variable depending on meteorological conditions. Atmospheric concentrations are commonly expressed in ppmv (parts per million by volume), where 1 ppmv […]
The ozone layer is essential to life on Earth. Although ozone (O₃) is present throughout the atmosphere, it reaches its highest concentrations in the stratosphere. This region is commonly referred to as the “ozone layer” (Figure 1) [1]. Figure 1: Ozone concentration as a function of altitude. The vast majority of ozone molecules are concentrated […]