Which of the following is true regarding "Global warming"?

• It is a gradual decrease in the average temperature of the earth which is why we experience colder winters now a days.
• The increase in greenhouse gases can be observed since industrial revolution took place.
• Much of the recent observed and projected global warming is natural. 

Only 2

Global warming is a gradual increase in the average temperature of the earth’s lower atmosphere as a result of the increase in greenhouse gases since the industrial revolution. Much of the recent observed and projected global warming is human-induced. It is caused by man-made increases in carbon dioxide and other greenhouse gases through the burning of fossil fuels and deforestation.