I think more than temperatures that this is the crux of the problem.When you're talking about a chaotic system a "right answer" is non-existent. You are setting the goalposts so high that they're unachievable. What they can do is come up with a best estimate. I see nothing wrong with their best estimate.
We do not yet know if there is a link between sunspots and earth climate. That is: all we have is correlation not causation. But suppose there is a cause/effect relationship (solar magnetism/GCRs is likely).
http://www.oar.noaa.gov/spotlite/archiv ... imate.html
(b) The globally averaged sea surface temperatures are plotted with the sunspot numbers (Reid; 1999). Both sunspot number and solar cycle length are proxies for the amount of solar energy that Earth receives. The similarity of these curves is evidence that the sun has influenced the climate of the last 150 years.
We have no way of predicting reliably future solar activity.Even the climate changes of the 20th century may have a significant solar component. Figure 3 shows comparisons of globally averaged temperature and solar activity. Many scientists find that these correlations are convincing evidence that the sun has contributed to the global warming of the 20th century. Some say that as much as 1/3 of the global warming may be the result of an increase in solar energy. So, while it is becoming clear that human activity is changing the climate today, solar activity may also be contributing to climate change and probably changed the climate in the past.
Given the above it is entirely possible that the effect of CO2 on climate is minor. And it is entirely possible that we are headed for cooling.
So let us look at the confounding factors so far. Ocean cycles - up to 50% of the warming. Solar cycles - up to 33% of the warming. If both of those are found to be at the top of the range than CO2 comes in at about 15% of the observed warming.
And of course on top of the cycles mentioned above there is chaos.
And then this:
http://www.unisci.com/stories/20022/0613022.htm
So far volcanic activity is unpredictable on longer time scales (decades - centuries - millenia)University at Buffalo scientists working with ice cores have solved a mystery surrounding sunspots and their effect on climate that has puzzled scientists since they began studying the phenomenon.
The research, published in a paper in the May 15 issue of Geophysical Research Letters, provides striking evidence that sunspots -- blemishes on the sun's surface indicating strong solar activity -- do influence global climate change, but that explosive volcanic eruptions on Earth can completely reverse those influences.
It is the first time that volcanic eruptions have been identified as the atmospheric event responsible for the sudden and baffling reversals that scientists have seen in correlations between sunspots and climate.
"Knowing the mechanisms behind past climate changes is critical to our understanding of possible future changes in climate, such as global warming, and for assessing which of these changes are due to human activities and which arise naturally," explained co-author Michael Stolz, doctoral candidate in the Department of Physics in UB's College of Arts and Sciences.
Best estimate? Possibly. If all known and predictable factors are included. But we know there are so far unpredictable factors. So the 90% confidence (how was that computed?) is a possibility given what the models cover. Real world? More like 10% or less.
You can't predict climate in any way unless ALL the major factors affecting it are included. And it is is CERTAIN all the factors are NOT included. And some known factors can not yet be predicted.