Here is a graph. It is of yearly global average PDSI, which is a soil moisture index, from around 1890 to 2005. The graph was generated from NCAR/UCAR data through climate explorer, http://climexp.knmi.nl/select.cgi?id=someone@somewhere&field=pdsi
The lower the index, the drier the soil.
The dataset is owned/collated by Aiguo Dai. It can be downloaded here:
http://www.cgd.ucar.edu/cas/catalog/climind/pdsi.html
(This is more up-to-date, but I do not have the tools/skills/intelligence to get it into what would be a user-friendly format for me)
NCAR is the National Centre for Atmospheric Research.
UCAR is the University Corporation for Atmospheric Research.
Information on both can be found here: https://www2.ucar.edu/about-us
What I believe that it shows is that the earth, on average, has been drying over the last three decades. What I am looking for in asking questions of lukewarmers and others is what kind of agreement we can come to on this drying and drying in the future.
I understand that the PDSI is not an absolute measure of dryness but a relative, so a wet area getting drier might be a good thing in agricultural terms, and that regardless we have much better technological and social solutions to drought now than we did in years past.
However, drought in crop-growing regions of the world still has major impacts for those who spend large portions of their income on food. This does not apply much to developed nations, but underdeveloped nations are vulnerable to shifts in global food prices.
I guess my first question would be: do you (and this question is directed at anyone interested) agree that the soils of the world appear to on average be getting drier?
See the ECMWF products. This link is for land only.
ReplyDeleteNot sure what PDSI is now, but it doesn't seem to jibe with the reconstructed precipitation record.
"However, drought in crop-growing regions of the world still has major impacts for those who spend large portions of their income on food. This does not apply much to developed nations, but underdeveloped nations are vulnerable to shifts in global food prices."
ReplyDeleteThis is a very complex issue made so in part because of the increased demand for food in the third world.
The scenario goes like this: They begin to develop industrially, they now have more money, they can afford a third meal in the day, historically they only had two. As the number of "they" who can afford three meals grows, aka the "middle class", the demand for food outstrips the availability of food very rapidly.
A report on this.
Other factors I've raised on Lucia's blog is plants care about water availability, and depending on the plant, it doesn't always need to be in the soil for the plant to utilize it (I gave the example of succulents).
Having looked at it, PDSI is the "Palmer Drought Severity Index". There are other indexes too. See here.
I would say I'm currently agnostic as to whether there is a loss of moisture or not. I don't think, based on my readings of it, that PDSI is a good indicator to use for that. Perhaps we can find one that is.
Broken link, Try again for discussion on PDSI and other indices.
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