There are many definitions for global warming which I will mention one of them.
Global warming is the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation.
Green House: A gas, like CO2, which traps the sun's heat.
There are a lot of causes for global warming but scientists proved that Carbon Dioxide (CO2) is one of the main causes of global warming however, there are natural for example the sun.
