Well --- will ya look at who ELSE never read AR5 ???
This difference between simulated and observed trends could be caused by some combination of (a) internal climate variability, (b) missing or incorrect radiative forcing, and (c) model response error.
The IPCC draws the following conclusion:
In summary, the observed recent warming hiatus, defined as the reduction in GMST trend during 1998–2012 as compared to the trend during 1951–2012, is attributable in roughly equal measure to a cooling contribution from internal variability and a reduced trend in external forcing (expert judgment, medium confidence). The forcing trend reduction is primarily due to a negative forcing trend from both volcanic eruptions and the downward phase of the solar cycle. However, there is low confidence in quantifying the role of forcing trend in causing the hiatus, because of uncertainty in the magnitude of the volcanic forcing trend and low confidence in the aerosol forcing trend.
Here is the relevant text from Chapter 9 of the WG I Report, that attempts to justify their final conclusion:
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). Depending on the observational data set, the GMST trend over 1998–2012 is estimated to be around one-third to one-half of the trend over 1951–2012 (Section 2.4.3, Table 2.7; Box 9.2 Figure 1a,c). For example, in HadCRUT4 the trend is 0.04 ºC per decade over 1998–2012, compared to 0.11 ºC per decade over 1951–2012. The reduction in observed GMST trend is most marked in Northern- Hemisphere winter (Section 2.4.3, (Cohen et al., 2012)). Even with this “hiatus” in GMST trend, the decade of the 2000s has been the warmest in the instrumental record of GMST (Section 2.4.3, Figure 2.19).
Nevertheless, the occurrence of the hiatus in GMST trend during the past 15 years raises the two related questions of what has caused it and whether climate models are able to reproduce it. Figure 9.8 demonstrates that 15-year-long hiatus periods are common in both the observed and CMIP5 historical GMST time series (see also Section 2.4.3, Figure 2.20; (Easterling and Wehner, 2009), (Liebmann et al., 2010)). However, an analysis of the full suite of CMIP5 historical simulations (augmented for the period 2006–2012 by RCP4.5 simulations, Section 9.3.2) reveals that 111 out of 114 realisations show a GMST trend over 1998–2012 that is higher than the entire HadCRUT4 trend ensemble (Box 9.2 Figure 1a; CMIP5 ensemble-mean trend is 0.21 ºC per decade). This difference between simulated and observed trends could be caused by some combination of (a) internal climate variability, (b) missing or incorrect radiative forcing, and (c) model response error. These potential sources of the difference, which are not mutually exclusive, are assessed below, as is the cause of the observed GMST trend hiatus.
How you like dem weak-ass excuses for the pause that I blew up in the above ---- eh?? The SUN has nothing to do with the warm-up since the LIAge ---- but NOW it can swamp out the signature of Global Warming when it takes a dive..
A NORMAL EXPECTED TINY dive at that.
Where was it in their modeling??
Contradicts the falsified radiative forcing for solar that the IPCC has attempted to repeatedly peddle..
And MAN -- that recent volcanic activity has been a rreal party poop hasn't it>??
The wizards of Oz took out statements about the pause in the Exec Summary as they appeared in most every released draft. Maybe you just never got further than that...
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