Science a GoGo's Home Page Forums General Discussion Climate Change Forum Issues with Global Land Surface Temp Trends

Thought this might be of interest to some.

http://blue.atmos.colostate.edu/publications/pdf/R-321.pdf

Unresolved Issues with the Assessment of Multi-Decadal Global Land-Surface Temperature Trends. 2006. Submitted to Journal of Geophysical Research.

Roger A. Pielke Sr., University of Colorado
Christopher A. Davey, Desert Research Institute
Dev Niyogi, Souleymane Fall, and Jesse Steinweg-Woods, Purdue University, Department of Earth and Atmospheric Sciences and Department of Agronomy
Ken Hubbard and Xiaomao Lin, School of Natural Resources, University of Nebraska-Lincoln
Ming Cai, Department of Meteorology and Young-Kwon Lim, Center for Ocean-Atmospheric Prediction Studies Florida State University.
Hong Li, Department of Atmospheric and Oceanic Science, University of Maryland
John Nielsen-Gammon, Department of Atmospheric Sciences, Texas A&M University College Station
Kevin Gallo, NOAA/NESDIS, Center for Satellite Applications and Research
Robert Hale, CIRA, Colorado State University
Jim Angel, Illinois State Water Survey, Dept. of Natural Resources
Rezaul Mahmood and Stuart Foster, Dept. of Geography and Geology, Western Kentucky University
Richard T. McNider, Department of Atmospheric Science University of Alabama
Peter Blanken, Department of Geography and Environmental Studies, University of Colorado

Abstract
The paper documents various unresolved issues in using surface temperature trends as a metric for assessing global and regional climate change. A series of examples ranging from errors caused by temperature measurements at a monitoring station to the undocumented biases in the regionally and globally averaged time series are provided. The issues are poorly understood or documented and relate to micrometeorological impacts due to warm bias in nighttime minimum temperatures, poor siting of the instrumentation, effect of winds as well as surface atmospheric water vapor content on temperature trends, the quantification of uncertainties in the homogenization of surface temperature data and the influence of land-use/land-cover (LULC) change on surface temperature trends.

Due to the issues presented in this paper related to the analysis of multi-decadal surface temperature we recommend that greater, more complete, documentation and quantification of these issues be required for all observation stations that are intended to be used in such assessments. This is necessary for confidence in the actual observations of surface temperature variability and long-term trends.

Wow, what a cool citation!

"surface atmospheric water vapor content" is important to 'snow water content' (as I found out this past winter).
I contribute to a rain & hail (and snow) monitoring network, and the LULC issues are very noticable, critical and problematic.

The very last chart in that 94 page paper showed a big difference after LULC corrections.

"The number of stations with significant trends (positive
or negative), prior to or after LULC changes, are indicated.
(number of stations with significant trends)

trend prior to LULC change:
neg 32, 9, 11; pos 33, 12, 20.

trend after LULC change:
neg 2, 8, 3; pos 110, 98, 110."

[respectively; min, max, mean;]

(from:)
min 32 33 2 110
max 9 12 8 98
mean 11 20 3 110

Wow! That's a big difference. I haven't read the paper, but I think this is saying there's a lot more positive significant trends. Positive means warming, right?

Regardless of the details of climate change overall, we see lots of examples of micro-ecosystems (like coral reefs, tree-lines, glaciers) that are sensitive to climatic shifts. All these 'canaries in the coal mine' are saying the same thing, aren't they?
For this snapshot in time, global warming is occurring. Shift happens.

Thanks again for the great link; more light reading!

~~SA

Have a read through the article. The table you referenced isn't before and after "corrections" to account for LULC issues. It is a comparision of the difference in trends before and after the LULC alteration.
I have to read it a couple more times to fully digest it.

But the main point of the paper is that LULC effects are not sufficiently taken into account when generating the global average temperature datasets.

G'day Canuck,

Thank you so much for the reference to this research. I hadn't come across it in my own research, which is strange considering what it addresses but you can never be sure of catching all research in a particular field no matter how good a periodic search is designed.

I'm going to have to read this in depth. It seems to me to be a fundamental area for any research on climate change yet seems to be neglected by almost everyone excepting for any research that aims to demonstrate that the data does not have a bias such as all the research published demonstrating just how small urban effect is on SAT data. Since this research also seems to directly address some issues in my own PhD proposal I'll be very interested to see what is said about any correction of deficiencies or methodologies that might be applied to reconcile the three major data sets of SAT currently being used, if this is addressed.

Regards


Richard

Hi Richard - glad to see you back on the forum.

The website I got this link from (can't remember which one, was randomly searching on methodologies for constructing global avg temps), Dr. Pielke did mention that this paper has been submitted to the Journal of Geophysical Research for review and publication. Apparently that submission was in Nov 2006. So it's very likely that this paper hasn't even been published yet, which would be the reason why you haven't come across it yet.

Just did a check on Dr. Pielke's website - there's an updated version
http://climatesci.colorado.edu/publications/pdf/R-321.pdf
February 2007 is the date of this one.

There looks like there's some other papers you might be interested in. For example "Documentation of uncertainties and biases associated with surface temperature measurement sites for climate change assessment". I might just have to go read that one.
Here's all his papers. http://cires.colorado.edu/science/groups/pielke/pubs/


As for those people who think urbanization does nothing to bias nearby climate stations - they must have never walked on asphalt on a sunny day, barefoot.

I've had "this thought" several times while reading these threads:
"Regardless of the details of climate change overall, we see lots of examples of micro-ecosystems (like coral reefs, tree-lines, glaciers) that are sensitive to climatic shifts. All these 'canaries in the coal mine' are saying the same thing, aren't they?" -21568,
and now (this thought) again while reading this paper. http://climatesci.colorado.edu/publications/pdf/R-321.pdf
Let me try to expound.

Trying to pin down the accuracy of our temperature measurements is a worthy goal; and it'll come in handy if we ever try to alter the climate on purpose and want to evaluate our results.
At this point, regardless of the accuracy, the precision (trends) of our measurements tell us things are changing.

Now I agree that, because of these concerns with the accuracy of the measurements and what we can deduce from those, it is problematic to use temperature data to "prove" the greenhouse effect is operating.

We need to be measuring enthalpy and not temperature to relate the measurements to the greenhouse effect.

...but IMHO:
Regardless of greenhouse effects, we are changing the environment (including climate) in way that make it warmer and dryer, less sustainable, less productive, and less resilient to climate forcers.
"Thus, if a surface measuring site (e.g., an HCN site) undergoes a local reduction in tree cover such that as a result 'q' decreases, then even if the value of 'H' were unchanged, there will be an increase in surface air temperature. The introduction of irrigation around the site, in contrast, will result in higher values of q, but a reduction of the surface air temperature." -p.15
[q = specific humidity; H = enthalpy]

I realize we do remarkable things with artificially increasing productivity in local areas, but if you subtract the energy required (fertilizers, etc.) to achieve that productivity, I think it'll be about neutral (or even a slight net loss) globally.
Trolling the lower reaches of the food chain, in order to produce large fish, is not sustainable or increasing our global productivity.

I can already see one potential flaw in this point, but I'm gonna leave that for later.

I hope the above is still a valid point after I finish reading the whole paper, but I'm just enjoying this too much not to write a little something.

*_*
Hey! As I write this, it occurs to me that there is a sort of see-saw between sustainability and productivity. Thus, many low productive systems would be more sustainable than an equivalently productive single system.
??

~SA

Which of the 325 papers in the second link were you specifically referring to?

Sorry, guess this highlighted fragment below is pretty vague, eh?

"Thus, if a surface measuring site (e.g., an HCN site) undergoes a local reduction in tree cover such that as a result 'q' decreases, then even if the value of 'H' were unchanged, there will be an increase in surface air temperature. The introduction of irrigation around the site, in contrast, will result in higher values of q, but a reduction of the surface air temperature." -p.15

Thanks for the browse, AR


~SA

You're welcome. I read every post and follow every link, though sometimes I don't read all of the links. Ninety pages in PDF format is a bit of a stretch even for me...but I do check out links. I've been known to delete postings or modify them in case the content was inappropriate. Just checking up on everyone. Don't feel picked-on, every link gets the same scrutiny. Just part of the job.

Amaranth Rose

Amaranth - I'm assuming you were responding to my post - since I think mine is the only one in this thread that had two links.

The second link is just to a list of papers that Dr. Pielke has authored, or co-authored. He seems to be fairly focussed on issues with calculating global average temps. Seeing how RicS is very interested in this work, I thought it appropiate to provide this link.

Sorry if I did something wrong.....

No, you didn't do anything wrong. I was just curious as to which paper you were directing attention to. Usually when one quotes a reference one has a specific paper in mind. Thanks for providing the link, I'm sure it will interest someone. I just wasn't about to read all 325 papers, that's all.

Amaranth

G'day all,

Canuck and Samwik, I have responded to both your posts in new threads because I thought that each specific topic should have a thread that concentrates on that topic. I hope you don't mind.


Regards


Richard