Linear equation avg. global temp.. Question below, doesn't make since.?

Question

In 1990, The Intergovernmental Panel on Climate Change predicted that the average temperature on Earth would rise 0.3 degrees Celsius per decade in the absence of international controls on greenhouse emissions.. Let "t" measure the time in years since 1970, when the average global temperature was 15 degrees Celsius.

A. Find a linear equation giving the average global temperature in degrees Celsius in terms of "t" the number of years since 1970.

Answer 1

I believe its

y=15+((t/10)*.3) or

y=15+.03t with y being temperature.