A few notes:

1) The existing GCM models do not handle major natural cycles like PDO/AMO well. This oversight is why there is so much uncertainty within the 'consensus' as to why the IPCC projections are failing to match reality.
2) The paper below purports to be able to model natural variability very accurately.
3) The same model - which takes into account major natural variability - then shows that of the overall warming that has been seen, more than half is due to natural variability.
4) This means that the effect of Anthropogenic CO2 is much less than has been pushed by IPCC. Rather than even 2 or 3 degrees C over 100 years (or more), it is at/under 1 degree C per 100 years. Or in other words, no big deal.

http://judithcurry.com/2013/08/28/pa...rface-cooling/

Recent global warming hiatus tied to equatorial Pacific surface cooling
Yu Kosaka and Shang-Ping Xie

Abstract. Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming, but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations.We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r 50.97 for 1970–2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southernUSA.Our results show that the current hiatus is part of natural climate variability, tied specifically to aLa-Nina-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.

The authors used the GFDL coupled global climate model. They conducted three simulations:

The historical (HIST) experiment is forced with observed atmospheric composition changes and the solar cycle. In Pacific Ocean–Global Atmosphere (POGA) experiments, SST anomalies in the equatorial eastern Pacific (8.2% of the Earth’s surface) follow the observed evolution (see Methods). In POGA-H, the radiative forcing is identical to HIST, and in the POGA control experiment (POGA-C) it is fixed at the 1990 value [natural internal variability only]. Outside the equatorial eastern Pacific, the atmosphere and ocean are fully coupled and free to evolve.


The results in terms of global-average surface temperature are shown in Fig 1 below:




In Fig 1 a, you can see how well the POGA H global average surface temperature matches the observations particularly since about 1965 (note central Pacific Ocean temperatures have increasing and significant uncertainty prior to 1980).
What is mind blowing is Figure 1b, which gives the POGA C simulations (natural internal variability only). The main ’fingerprint’ of AGW has been the detection of a separation between climate model runs with natural plus anthropogenic forcing, versus natural variability only. The detection of AGW has emerged sometime in the late 1970′s , early 1980′s.

Compare the temperature increase between 1975-1998 (main warming period in the latter part of the 20th century) for both POGA H and POGA C:


  • POGA H: 0.68C (natural plus anthropogenic)
  • POGA C: 0.4C (natural internal variability only)


{i.e. man-made CO2 emissions only accounts for 41% of warming}
Net net - this paper is 'consensus' in the sense that it sees a resumption of warming due to CO2 emissions, but it simultaneously destroys the political consensus because the estimated effects of man-made CO2 emissions is relatively minor. Or in other words, the IPCC and consensus that man-made CO2 emissions are the primary/largest driver of temperature increases is wrong.