reply to post by Rezlooper
Unbelievable weather we've been through? Mildest winter I've ever experienced in my 30 years on this planet. I went out the other day in just a jumper, and was almost too warm.
It's not an easy task to reconcile increasing discrepancies and uncertainties with the increased confidence in past and future projections. But they somehow managed it.
It should be noted that there are no instances in the figure for which CMIP5 models perform worse than CMIP3 models (something that would have been indicated by the red colour). A description that explains the expert judgment for each of the results presented in Figure 9.44 can be found in the body of this chapter, with a link to the specific sections given in the figure caption.
So, yes, climate models are getting better, and we can demonstrate this with quantitative performance metrics based on historical observations. Although future climate projections cannot be directly evaluated, climate models are based, to a large extent, on verifiable physical principles and are able to reproduce many important aspects of past response to external forcing. In this way, they provide a scientifically sound preview of the climate response to different scenarios of anthropogenic forcing.
An El Niño occurs when warm water buried below the surface of the Pacific rises up and spreads along the equator towards America.
I'm not sure where you get "increasing discrepancies and uncertainties" from but yes, it says that some aspects of some models should be adjusted so that they better fit observations.
This downward scaling is, however, not sufficient to explain the model-mean overestimate of GMST trend over the hiatus period.
They "managed" it because when all available information is considered, there is a warming trend and there is not evidence that there are factors other than increasing CO2 levels sufficient to account for it.
Observed global mean surface temperature show flat trends since 2001 in all (3) data sets the IPCC uses for model-data comparsions.
And, indeed, one of the flaws of CIMP5 models is their inability to predict short term internal variability.
Hiatus periods of 10 to 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 to 15 years for long-term climate change (Box 2.2, Section 2.4.3). Furthermore, the timing of internal decadal climate variability is not expected to be matched by the CMIP5 historical simulations, owing to the predictability horizon of at most 10 to 20 years (Section 11.2.2; CMIP5 historical simulations are typically started around nominally 1850 from a control run). However, climate models exhibit individual decades of GMST trend hiatus even during a prolonged phase of energy uptake of the climate system (e.g., Figure 9.8; Easterling and Wehner, 2009; Knight et al., 2009), in which case the energy budget would be balanced by increasing subsurface–ocean heat uptake (Meehl et al., 2011, 2013a; Guemas et al., 2013).
And, indeed, one of the flaws of CIMP5 models is their inability to predict short term internal variability
The inconsistency between observed and simulated global warming is even more striking for temperature trends computed over the past fifteen years (1998–2012). For this period, the observed trend of 0.05 ± 0.08 °C per decade is more than four times smaller than the average simulated trend of 0.21 ± 0.03 °C per decade. It is worth noting that the observed trend over this period — not significantly different from zero — suggests a temporary ‘hiatus’ in global warming.
The divergence between observed and CMIP5-simulated global warming begins in the early 1990s, as can be seen when comparing observed and simulated running trends from 1970–2012.
The evidence, therefore, indicates that the current generation of climate models (when run as a group, with the CMIP5 prescribed forcings) do not reproduce the observed global warming over the past 20 years, or the slowdown in global warming over the past fifteen years.
The models can show the occurance of short term flattening of the trend, but they have hard time predicting them.
reply to post by Rezlooper
Why on Earth would you post that picture? You don't think it's real do you?
Posting that sort of crap really doesn't help your (our) credibility.
edit on 2/11/2014 by Phage because: (no reason given)