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Lucia Liljegren has wonderfully clear post up which explains issues of consistency and inconsistency between models and observations using a simple analogy based on predicting the heights of Swedes.

She writes;

I think a simple example using heights is helps me explain the answer to these questions:

1. Is the mean trend in surface temperature over time predicted by the IPCC consistent with the temperature trends we have been experiencing? (That is: is 2C/century consistent with the trend we’ve seen? )
2. Is the lowest uncertainty bound the IPCC shows the public consistent with the trend in GMST (global mean surface temperature) we have seen since 2001?

I think these questions are important to the public and policy makers. They are the questions people at many climate blogs are asking and they are the questions many voters and likely policy makers would like answered.

I think the answer to both questions is “No, the IPCC predictions are inconsistent with recent data.”

Please go to her site and read the entire post.

She concludes her discussion as follows:

The IPCC projections remain falsified. Comparison to data suggest they are biased. The statistical tests accounts for the actual weather noise in data on earth.

The argument that this falsification is somehow inapplicable because the earth data falls inside the full range of possibilities for models is flawed. We know why the full range of climate models is huge: It contains a large amount of “climate model noise” due to models that are individually biased relative to the system of interest: the earth.

It will continue to admit what I have always admitted: When applying hypothesis tests to a confidence limit of 5%, one does expect to be wrong 5% of the time. It is entirely possible that the current falsification fall in the category of 5% incorrect falsifications. If this is so, the “falsified” diagnosis will reverse, and not we won’t see another one anytime soon.

However, for now, the IPCC projections remain falsified, and will do so until the temperatures pick up. Given the current statistical state ( a period when large “type 2″ error is expected) it is quite likely we will soon see “fail to falsify” even if the current falsification is a true one. But if the falsification is a “true” falsification, as is most likely, we will see “falsifications” resume. In that case, the falsification will ultimately stick.

For now, all we can do is watch the temperature trends of the real earth.