1992 because it's the first report.

Here's a decent summary: https://en.wikipedia.org/wiki/Global_warming_hiatus

'climate is classically averaged over 30-year periods.[5]'

'Publicity has surrounded claims of a global warming hiatus during the period 1998–2013. The exceptionally warm El Niño year of 1998 was an outlier from the continuing temperature trend, and so subsequent annual temperatures gave the appearance of a hiatus: by January 2006, it appeared to some that global warming had stopped or paused.[2] A 2009 study showed that decades without warming were not exceptional,[6] and in 2011 a study showed that if allowances were made for known variability, the rising temperature trend continued unabated.'

Essentially in 5 years we'll have enough data to confirm / deny the 1992 predictions, currently it's an unproven theory because of a lack of forward data. We're essentially using consensus as a proxy for a falsification of the null hypo