Starting the causes, one major cuase is the carbon dioxide emissions. In fact, the Carbon Dioxide emissions are over 6500 million tons per year over the last 200 years.
Yet another cause is that the CO2 and NOx concentrations in the atmosphere are still increasing.
Shifting to effect, there are two major effect of this issue. First, the tempreture. The truth is the increasnment of the tempreture on the earth is predected to be about 3° to 5° C (34° to 41° Fahrenheit) by the year 2100. The second is the sea level. It will rise by at least 25 meters (82 feet) by the year 2100.
To conclude, if we act fast we can atleast control this issue.
Reference:
http://timeforchange.org/cause-and-effect-for-global-warming