"Temperature decline" refers to a decrease or a drop in temperature over time or in a specific area. It means that the temperature is getting cooler or colder. Full definition
Global temperatures declined as CO2 levels increased, so they switched from global warming to climate change. (drtimball.com)
How do you explain an eight year global mean temperature decline in the face of an increasing human CO2 increase? (hubpages.com)
The application of trends to climate data began in the 1970s with the prediction of a coming ice age as temperatures declined from 1940. (drtimball.com)