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.
Predictions of massive species extinctions due to AGW came into prominence with a January 2004 paper in Nature called Extinction Risk from Climate Read more [...] 25 com
Some 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 Read more [...] 23 com
The theory of this Israeli astrophysicist has gained traction as the great white hope of climate skeptics. Below are some sources of background reading.
Shaviv champions the solar-wind modulated cosmic ray flux (CRF) hypothesis, which was suggested by Ney, discussed by Dickenson, and furthered by Svensmark (see CO2 Science). Evidence consistes of correlations between CRF variations and cloud cover, correlations between non-solar CRF variations and temperature over geological timescales, as well Read more [...] 28 com
The 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:
Scientists say Australia, with its harsh environment, is set to be one of the nations most affected by climate change.
â€œContinued increases in greenhouse gases will lead to further warming and drier conditions in southern Australia, so the [fire] risks are likely to slightly worsen,â€ Read more [...] 16 com
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:
The percentage of droughted area appears to be a â€™bounded extreme value, peaks over thresholdâ€™ or bounded POT statistic. The Read more [...] one
One 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.
From the Summary of chapter 9 of my book, niche-modeling-chap-9
These results demonstrate that procedures with linear assumptions are unreliable when Read more [...] 5 com
The 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".
Who said statistics lie?
Translation: "VO: The updated Read more [...] 2 com
"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
If ever there was a good example of alarmists views being given a free ride by a major journal, then the publication in Science of "Recent Climate Observations Compared to Projections" by
Stefan Rahmstorf, Anny Cazenave, John A. Church, James E. Hansen, Ralph F. Keeling, David E. Parker, and Richard C. J. Read more [...] 29 com
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!
Below are three different methods with slightly varying end point treatments. Two are causal smoothers (SSA and spline) and one is acausal (moving average). Causal smoothers Read more [...] 2 com
Well 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.
Update: Stefan Rahmstorf replied at the post here.
To provide a bit more clarity, I have drawn a couple of lines on the Read more [...] one
Here I show more humorous effects of smoothed trend lines with the 'minimum roughness condition' (MRC). The confidence limits blow out.
Fitting a straight line to data such as global temperature data is a common linear regression example problem. Linear regression of stock prices tells you your rate of appreciation. Smoothing, (or filtering) is used to give a smooth, curved trend instead of a straight regression line. Instead of applying a linear regression model to data many techniques such Read more [...] 7 com
There appears to be an error in the influential paper by Rahmstorf et al. (2007). Rahmstorf et.al. (Science Brevia, 4 May 2007, p709 ) 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, Read more [...] 54 com