It isn't clear to me where the suggestion that solar activity accounts for temperature increase up to 1998 is comming from. Nor do I see any suggestion that it is responsible for the modest temperature decline since 1998.
I think Turtle is alluding to the Maunder Minimum,
Maunder Minimum - Wikipedia, the free encyclopedia
and the controversy over the correlation of minimal sunspot activity with the little ice age event. It is my understanding that the earth has been recovering from this event, at least up until 1998, when the temperature peaked.
Is this your understanding as well?
EDIT: Didn't see your post, Turtle.
