Answer:
I'm assuming this means concentrations of the atmosphere*
Step-by-step explanation:
Carbon dioxide are both considered greenhouse gasses. This means whenever they are in the atmosphere, they absorb heat from the sun and trap it within the atmosphere. In general, greenhouse gasses are a good thing. They trap heat in the Earth during nighttime so we do not freeze when we don't have the sun. However, since the Industrial revolution, the overuse of fossil fuels which are made of carbon and sometimes have high methane concentrations have lead to an excess amount of these gasses in our atmosphere. If concentrations become too high, the Earth's climate will continue to display higher average temperatures, leading to a complete change in our environments as once glacial areas will begin to display more temperate climates, and temperate and warm climates will become even hotter. Ecosystems in every area will be severely damaged, with many species likely facing extinction. Additionally, sea levels will rise much higher, both due to the melting of glaciers into the ocean and also because warmer climates will make the ocean warmer, meaning the molecules of water will spread farther apart and increase the volume of the ocean.