Over the last couple of months there has been much blog - viating about what the models used in the IPCC 4th Assessment Report (AR4) do and do not predict
about natural variability in the presence of a long - term greenhouse gas related trend.
«We're talking about relatively subtle levels of warming, where we have to really think much
harder about natural variability and so forth to take that into account when we're talking about the risks at these different levels of warming.»
When we
talk about natural variability and reference examples such as the MWP and the LIA, we are talking about what Earth has achieved without human help (no manmade GHGs).
Data over 140 years is insufficient to make over broad
claims about natural variability and it would require a leap of imagination to use this data in and of itself to draw conclusions about cause and effect.
If you want to know what I think about the science of climate change, then you should read what Mojib (if my name weren't Mojib Latif it would be global warming) Latif has to say about the relationship between natural variability and long - term climate change (which includes, very prominently, the
discussion about natural variability «swamping» mean surface temperature on a short - term basis).
About natural variability and sensitivity for man - made GHGs, here I disagree with Raypierre in another (large) comment...