When we burn fossil fuels (oil, coal, natural gas) to run our cars, homes and industries, we produce increased amounts of carbon dioxide and other gases that persist in the atmosphere and trap heat.
The effect has been likened to how the glass of a greenhouse traps heat from incoming sunlight; thus the gases responsible are known as “greenhouse gases”.
In addition to a higher average global temperature, evidence for global warming includes reduction in the extent of snow and ice cover, and rising sea levels.