Is drought frequency something that should be used at present to assess climate models?

Question

A skeptic recently used drought frequency as an example of something that climate change alarmists had gotten wrong in terms of prediction. While nearly all climate models predict that increased severity and frequency of drought will be a consequence of global warming, it is not clear that we should be able to see these changes yet. The following paper:

http://ruby.fgcu.edu/courses/twimberley/EnviroPhilo/Drought.pdf

discusses in great detail the results of several climate model simulations of drought. Figure 13 shows when we might expect these changes to be detectable over the background variability in climate, with the mean timeframe for detectability no earlier than 2020 in terms of a global average (and this is if we choose to accept the bare minimum in statistical significance for detection (which I'm sure skeptics would be willing to do, right?)). This means that there is so much natural variability in the frequency and severity of droughts that we really should not expect to see the warming signal in drought statistics for at least another decade (probably several decades to satisfy the skeptics (oh, what am I thinking, they will never accept it but you get the point)). Meaning that any use of drought as proof or disproof that climate models are accurate (or that warming is occurring if one accepts climate models have the drought prediction correct) is at best premature.

So, should the skeptic have used drought as an example in his argument? If he did, and he is aware of this problem in detectability, would this be an example of a skeptic using deceptive logic and fallacy to make a political point? Alternatively, is the skeptic simply ignorant of the concept of detectability. If it's the latter, does anyone think the skeptic will cease to use drought statistics in the context of a failed prediction or will we continue to see it used like this?

As an aside, this is probably behind a pay wall for most people, but as an interesting aside, this paper:

http://journals.ametsoc.org/doi/pdf/10.1175/2007JCLI1822.1

(Sheffield and Wood, J. Climate, 2007, 21: 432-458) shows trends in droughts goth globally and broken down by region. The interesting thing is that while some regions do show a decrease in drought, this decrease is an overall trend beginning in the early 1900's. There are many regions however, that show a large increase in drought frequency towards the end of the 1900's that looks suspiciously similar to the rise in global mean temperature. (See Figure 7, if you can get to the paper.)

Answer 1

To answer your question, most of the uneducated deniers here do somehow try to imply that because the earth is not burning up, our grandchildren have nothing to worry about. These people just want to argue, they have no interest or ability to digest complex information.



But, a change in the water cycle has indeed been identified by measuring changes in ocean salinity. The salinity is changed place to place by the amount of fresh water run off. The general conclusion is that the water cycle is intensifying and that wet places are getting wetter and dry places drier, between 1900 and that the changes are actually happening twice as fast as the climate models have predicted.



http://www.sciencemag.org/content/336/6080/455.abstract?sid=0d23d1f1-5a50-4be8-9f49-df14324bee61

Answer 2

"There are many regions however, that show a large increase in drought frequency towards the end of the 1900's that looks suspiciously similar to the rise in global mean temperature. (See Figure 7, if you can get to the paper.)"



This is the fallacy. Because some regions may indeed have increase droughts with higher temperatures, you assume that ALL regions will experience this. Although I am also sure that if all regions experienced drought frequency with a rise in global temperatures, you would point out these studies that say so, do your little victory dance and proclaim anybody who does not agree with this as being a big oil stooge denier.

Answer 3

All types of measurement have value, even if the signal-to-noise ratio (SNR) is less than 1 for some of them. Suppose that 100 different physical measurements are made and one of them is drought frequency. (100 is used for illustrative purposes only, the actual number to use is the number of data sets.) It is possible to mean center and normalize all of the measurements as dimensionless variables by subtracting the mean value and then dividing by the standard deviation for each variable. The models cited predict that the drought frequency variable will have a value of less than 1.0 at present. However, if there is a valid underlying trend, there will be correlations between variables that can be exploited, even if none of the variables is in isolation statistically significant. For example, the Maximum Entropy method was developed by radio astronomers to extract signals from data with a SNR in any single channel of 0.001. My favorite is Principle Component Analysis (PCA) which I use to classify tissue samples based on hundreds of spectral measurements. The PCA method uses the covariance between measurements to identify a small set of orthogonal vectors (which are linear combinations of the original data set) that explain most of the variance. 100 measurements would give a 100-dimensional data space. The PCA method typically concentrates 90% of the variance in the first 3 vectors (PC!, PC2, PC3) of the new set and the remaining 97 describe noise. If AGW is not happening, the 3D vectors (PC1,PC2,PC3) for each year will be distributed in an isotropic cluster. If AGW is happening, the 3D vectors (PC1,PC2,PC3) will show a statistically significant trend with time. The short answer is yes, drought frequency data can be used, but not in isolation.

Answer 4

KI am sure drought frequencies were built into the models to determine areas where droughts have occurred and their severity. Models vary based on their planned output, whether that be drought or temperature etc. A simple google of drought and climate change will give you real time info on drought instead of supposition.



You strike me as a denier, you ask a question but then you have four paragraphs which more than anything are cementing your personal opinion of the links you provide.

Answer 5

Usually it use only to rise price on water utility and rise in taxes. As far as I know.