'Box 9.2: Climate Models and the Hiatus in Global-Mean Surface Warming of the Past 15 Years
The observed global-mean surface temperature (GMST) has shown a much smaller increasing linear trend over the past 15 years than over the past 30 to 60 years (Section 2.4.3, Figure 2.20, Table 2.7; Figure 9.8; Box 9.2 Box 9.2 Figure 1a,c).'
'Hiatus periods of 10–15 years can arise as a manifestation of internal decadal climate variability, which sometimes enhances and sometimes counteracts the long-term externally forced trend. Internal variability thus diminishes the relevance of trends over periods as short as 10–15 years for long-term climate change (Box 2.2, Section 2.4.3).'
http://www.climatechange2013.org/images/uploads/WGIAR5_WGI-12Doc2b_FinalDraft_Ch...So the hiatus is the change in the trend. If we compare the trend 1979-1998 to 1998-current; the trend has changed. there is an hiatus. The IPCC admits to this. There have been over 50 papers attempting to explain this.
Apparently natural variation can explain the hiatus, but can't explain any speed up in climate change; it is a one way only variation. (Sarc)
Then of course if we look at the early 20th century warming trend 1918-40 (approx), the trend is very similar. But IPCC says CO2 only caused the spike in the second half of the century. What caused the early 20th century warming?
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