1998 was the last warmest year, so doesn’t that mean we are in Global Cooling since then? Yes/No?
The 1998 data was misinterpreted by NASA. A 15 year old German kid found the error and NASA was forced to correct the date. That made a much earlier year the hotest. The global warmers still claim 1998 even though they know better.
But to answer your question, if 1998 were the hotest year ever, it would prove there has been no warming over the last 10 years.