The message
from "The Medway Handyman" contains
these words:

If the greenhouse effect is real, and it has been accepted as fact for
over a century,

What? Since 1908?

No, earlier.

Per Wikipedia:

"The greenhouse effect was discovered by Joseph Fourier in 1824 and
first investigated quantitatively by Svante Arrhenius in 1896.[2]

In the absence of the greenhouse effect, the Earth's average surface
temperature of 14 °C (57 °F) would be about -18 °C (–0.4 °F) [3]
[4](Black body temperature of the Earth). "

How come I've never heard of it until recently?

That is a question only you can answer.

--
Roger Chapman