global warming 
noun [mass noun]
A gradual increase in the overall temperature of the earth’s atmosphere generally attributed to the greenhouse effect caused by increased levels of carbon dioxide, CFCs, and other pollutants.The company is deeply concerned by the effects of global warming caused by the greenhouse effect....
- Some climatologists maintain that global warming is unlikely to have an impact on hurricanes.
- The tired old global warming, and greenhouse gas bogeymen have also been raised.