Since 2006, in between promoting numeracy in education, and examples of simple statistics using topical issues from the theory of Anthropogenic Global Warming (AGW) to illustrate points, I asked the question “Have these models been validated?”, in blog posts and occasionally submissions to journals. This post summarizes these efforts.
CommentsSome time ago I had a brief discussion with Leif Svalgaard on ClimateAudit blog inspired by an exchange between Leif and David Archibald when the latter complained that Leif’s TSI reconstruction was “too flat”.
The sunspots exhibited cyclic variability in terms of the frequency of the cycles and that most thermostats work by pulse width modulation and some digital music with pulse frequency modulation. Both these work in a similar manner the thermal inertia of whatever the thermostat is controlling smooths the temperature variability and the pulse frequency modulation’s demodulator is a simple low pass filter often just a series resistor and shunt capacitor. In both these cases only the duty cycle or the frequency varies but not the amplitude. Below is a description of how this behaviour can be simulated with an electrical circuit emulator called ‘qucs’.
CommentsThe theory of this Israeli astrophysicist has gained traction as the great white hope of climate skeptics. Below are some sources of background reading.
CommentsThe Financial Times recently reported on the Australian bushfires, linking them to increases in greenhouse gases. We take another look at the data in the DECR and find Australia is getting wetter not drier:
CommentsHere are my comments on the reviewers 1 comments on the manuscript submitted to AMM about the DECR. The summary of the manuscript stated:
CommentsThe 2008 Drought Exceptional Circumstances Report (DECR) makes a number of bold claims in its assessment of likely changes in the frequency and severity of severe rainfall deficiencies over the next 20-30 years. This review presents an analysis which brings into question whether these claims can be sustained by the data. Taking into account the poor performance of climate models, as evidenced by simulations of area of exceptionally low rainfall trending in the opposite direction to observations, a more valid interpretation of the data would be for drought frequency and severity in Australia to remain largely unchanged in the future, with no expectation of a change in the climatological basis for EC declarations.
A number of familiar tests, often used to evaluate the performance of models: R2 correlation, Nash-Sutcliffe efficiency and similarity of trends and return period, were reported here, noting not much evidence of skill in the DECR models compared with observations at any of these. I also said what a better treatment might entail but left that for another time:
CommentsOne of the main assumptions of linear regression is, ahem, linearity. Here is an example drawn from dendroclimatology, the reconstruction of past climates using tree rings, of the trouble one can get into by blindly assuming linearity. This subject was dealt with some time ago at ClimateAudit Upside-Down Quadratic Proxy Response.
CommentsA number of readers have expressed some knowledge of the greenhouse effect and how it works. Here is a quiz to give the punters an opportunity to show they know what they are talking about.
CommentsThe sharp-eyed UC who keeps a good technical blog on signal theory alerted me to this intelligent reference in the Finnish media to Rahmstorf et al. 2007. This is a paper I have reviewed previously and had words with Stefan at RealClimate demonstrating they had grossly underestimated the uncertainty at the end points. This flawed paper is widely quoted to justify claims that the climate system is “responding more strongly than we thought”.
Comments“According to a new U.N. report, the global warming outlook is much worse than originally predicted. Which is pretty bad when they originally predicted it would destroy the planet.” –Jay Leno
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How much error is there in smoothed climatic and financial series? How much does variability at the ends of the series affect the trend as a result? Here we showed that certain ways of treating the end points introduce a lot of variability. Here we show in certain smoothers variability at the ends can affect the whole smooth! Read the rest of this entry…
CommentsWell it is almost 24 hours since I posted the comment below to RealClimate at the post by Stefan Rahmstorf, about the inconsistency in the methodology used in their Science Brevia article to show that climate is trending higher than IPCC models. As yet the post has not appeared. I can’t see how it breeches their moderation policy, so I guess I am being told to go pound sand. Read the rest of this entry…
CommentsHere I show more humorous effects of smoothed trend lines with the ‘minimum roughness condition’ (MRC). The confidence limits blow out. Read the rest of this entry…
CommentsThere appears to be an error in the influential paper by Rahmstorf et al. (2007). Rahmstorf et.al. (Science Brevia, 4 May 2007, p709 [1]) reports that the trend of the global mean of surface temperature and sea level raise concerns that the climate system “may be responding more quickly to climate change than our current generation of models indicates”. At least one major study, Interim Report of the Garnaut Review, relies on the paper for advocating prompt and extreme action on carbon emissions, one of its major conclusions (Section 2.4 Consequences of Climate Change, Observed Climate Change). But there seems to be a problem. Read the rest of this entry…
CommentsUpdate: See “Recent Climate Observations: Disagreement With Projections” 2009, Energy & Environment.
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