Global warming is an average increase in the temperature of the atmosphere near the earth's surface, which can lead to changes in global climate patterns.
Causes of environmental crisis:

1. Rapid growth of world population placing increasing scarce resources is degrading the global ecosystem.
2. Carbon emission have greatly increased over the past 200 years.

The problem of environmental crisis has emerged in recent times because discovered coal, factories and motor vehicles, leading to more of carbon dioxide in the environment. Increased population wants to live with refrigerators, televisions and motor vehicles with air conditioning.
This puts tremendous pressure on governments all over the world to provide more and more electricity. Most electricity is produced by burning coal and other fossil fuels. Thus, the greatest advances in humanity's capacity to harness energy and meet its own ends has led to environmental crisis in recent times.