Introduction
The greenhouse effect is a natural phenomenon that regulates the temperature of a planet (or satellite) with an atmosphere. This phenomenon involves the accumulation within the atmosphere of a part of the thermal energy coming from the star around which the celestial body orbits, due to the presence of certain gases in the atmosphere, known as "greenhouse gases."
Greenhouse gases allow the entry of solar radiation from the star, while hindering the passage of infrared radiation emitted from the surface of the celestial body. This leads, on one hand, to an increase in the temperature of the celestial body involved in the phenomenon and, on the other hand, to less intense thermal excursions compared to those that would occur in the absence of the greenhouse effect.
The greenhouse effect, as a natural phenomenon, is essential for the presence and development of life on Earth. Conversely, the increase in the greenhouse effect, which is caused by human intervention in nature, altering the normal thermal balance of the planet, has led over the years to significant climatic and environmental changes, resulting from consequent global warming.
The main greenhouse gases are:
- Water vapor, which accounts for about 70% of the greenhouse effect.
- Carbon dioxide and methane, which together represent 25% of the greenhouse effect.
- Others include nitrous oxide (N2O), chlorofluorocarbons.
The main cause that disrupts the balance of greenhouse gases in the atmosphere is human actions. Anthropogenic activities are indeed directly responsible for the excessive increase of gases in the atmosphere and their negative effects on our climate. The primary contributor to the greenhouse effect is the excessive use of fossil fuels. Another factor that disrupts the balance of the natural greenhouse effect is deforestation. To limit the greenhouse effect, some individual actions can be taken such as reducing meat consumption and eating seasonal fruits and vegetables.
Technical Insight: Radiative Forcing
Radiative forcing is a key concept in climatology and represents the measure of the influence of a factor, such as the increase in carbon dioxide or other greenhouse gases in the atmosphere, on the alteration of the balance between incoming and outgoing energy in the Earth-atmosphere system.
The radiative forcing of CO2 is particularly important. CO2 is essentially transparent to solar radiation, but absorbs infrared radiation. This means that while it allows the entry of solar energy, it hinders the release of heat radiation outward. This behavior results in a positive radiative forcing, contributing to global warming.
Radiative forcing measures the alteration that a chemical species causes in the Earth's energy balance, i.e., its contribution to additional greenhouse effect. This energy flux is measured in watts per square meter (W/m²). In the context of climate change, a more specific definition of radiative forcing, agreed upon by the Intergovernmental Panel on Climate Change (IPCC), is the measure of how a factor alters the energy balance in the troposphere, the lowest level of the atmosphere.
It is important to note that human activities are significantly contributing to positive radiative forcing, leading to a global increase in temperatures. The combustion of fossil fuels since the industrial revolution has increased the amount of some gases, particularly carbon dioxide (CO2), in the atmosphere.
