15 - Radiative Forcing

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The Earth receives energy from the Sun and radiates it back to space in the form of infrared rays. It should be in a state of thermal equilibrium and the average temperature should be constant. Anything that causes the Earth to move away from this thermal equilibrium, whether natural (sun, volcanoes) or anthropogenic (aerosols, GHGs), is called radiative forcing. Caution: the definition has been simplified for educational purposes. A rigorous definition would be as follows: "Radiative forcing is the measure of the imbalance between the energy that arrives every second on Earth and the energy that would leave if the temperature had remained fixed since 1750". As the earth's temperature has risen in the meantime, the delta between instantaneous heat exchanges has decreased. Similarly, in 2050, in the RCP2.6 scenario, the forcing will be 2.6 W/m2, but the temperature will have stabilised, meaning that the delta between incoming and outgoing energy will be zero. On the main graph, we can see the different components of the radiative forcing: in the upper part, the warming effects in the lower part, the cooling effects. The greenhouse effect (CO2 + Other WMGHG + Trop O3) represents a positive forcing of 3.1 W/m2. It is therefore in the upper part of the graph. Aerosols (Aer - Rad Int. + Aer - Cld Int.) have a cooling effect and are therefore in the lower part of the graph.

Earth from Space
The radiation budget’s delicate balance is a key factor in regulating Earth’s climate – the budget integrates almost all of the physical processes affecting Earth’s climate. The radiation budget refers to the equilibrium between the incoming solar radiation from the Sun and the outgoing thermal radiation emitted by the Earth. This balance is crucial for maintaining a relatively stable temperature on our planet and is influenced by various factors, including clouds, aerosols, greenhouse gases and surface properties. Understanding and monitoring Earth's radiation balance is crucial for studying and addressing climate-related issues. ESA’s EarthCARE mission carries a suite of instruments to answer critical scientific questions related to the role that clouds and aerosols play in reflecting incident solar radiation back out to space and trapping infrared radiation emitted from Earth’s surface. Although clouds play an extremely important role in atmospheric heating and cooling, they remain one of the biggest mysteries – in fact the least understood factor – in our understanding of how the atmosphere drives the climate system.
Credits :© ESA/ATG medialab
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2
Causes

Radiative Forcing

Aerosols cool down the climate.

Radiative Forcing

The expression "Greenhouse Effect" is written on both sides (as of last version, October 2018).

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Consequence

Energy Budget

Radiative Forcing

The text behind card n14 allows no ambiguity. Therefore the 2 cards have to be skipped together or not at all.

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Other possible cause

Radiative Forcing

When the ice pack melts, a white surface is replaced by a dark blue surface, which has a lower albedo and therefore absorbs more energy. This relationship is not essential but it does allow another feedback loop of the game to be put forward.