En-en adult card 14 energy budget
Card #14: Energy Budget
This graph explains where the energy accumulated on Earth due to radiative forcing goes :
it warms up the ocean, melts ice, dissipates into the ground, and warms up the atmosphere.
On the graph, you can see several colours that represent, from top to bottom:
- In light blue, the upper layer of the ocean, between 0 and 700m
- In dark blue, the lower layer of the ocean, between 700m and 2000m
- In white, the different types of ice
- In orange, the soil
- In purple, the atmosphere.
The dotted lines represent uncertainty.
If you choose to keep this card, you need to remember the first principle of thermodynamics: energy is conserved. Players may draw links from Energy budget to Increase in Water Temperature and Temperature Rise, then links from Temperature Rise to Melting of glaciers and Increase in Water Temperature to Melting of Sea Ice and Melting of Ice Sheets. By doing this, they consider that the air and water warm up, and then they melt the pack ice, glaciers and ice caps. But if a calorie has passed through the water and finally contributes to melting the pack ice from below, then it is no longer in the water.
A tip to simplify the explanation of this card is to rename the following cards. An increase in temperature is an increase in energy, and melting is also an increase in energy. The five cards then become Increase in the energy level of water, air, sea ice... And the players will understand that these five cards have to be put at the same level. So if a calorie that is in the water contributes to melting the pack ice, once the pack ice has melted, this calorie is no longer in the water. The water has cooled down. In this case, should the calorie be counted in the "ocean" or "melting ice" part? Answer: in the melting part of the ice. You can't count this calorie twice.
To go further
Oceans cover 71% of the earth's surface, with an average depth of 4 km. If air were reduced to the same density as water, its height would be 10m. The ocean has a very high density, which explains why it absorbs most of the energy related to GHGs emitted by man.