Question

explain global warming and effect of greenhouse gases

Answer 1

here is the answer of your question:
global warming means the continuous increase in the temperature of the earth due to greenhouse gases like methane,carbon dioxide emissions from factories,chimneys etc.

Answer 2

Global warming is a long-term rise in the average temperature of the Earth's climate system, an aspect of climate change shown by temperature measurements and by multiple effects of the warming. 
 The net effect is the gradual heating of Earth's atmosphere and surface, a process known as global warming. These greenhouse gases include water vapor, CO2, methane, nitrous oxide (N2O) and other gases, according to the Environmental Protection Agency (EPA).