Saturday, January 16, 2010

Seeking inputs on UHI corrections.

[From Rick] This post seeks inputs on the status of Urban Heat Island (UHI) correction in temperature reconstructions. The information I have is a bit dated and sounds as though it might be one-sided. [Figure above is from Steve McIntyre. It is found in both of the Climate Audit links below.]

In any case, here's what my limited data collection has in it:

I mentioned to Ira having seen something on the difference between NOAA's and NASA's (GISS) use which I found at Climate Audit: NOAA versus NASA-1/20/09. McIntyre also refers to a post a few days earlier with a bit more data: Climate Audit: NOAA versus NASA-1/16/09


The figure above suggests that the NOAA temperature dataset from about 1930-1940 to be 0.1°C colder than the GISS dataset - and by 2000, 0.2°C warmer than the GISS. If I'm interpreting this correctly, the NOAA chart would suggest more warming than GISS of about 0.3°C (0.5°F) over the last 70 years. This 0.3°C difference MIGHT be the effect of GISS attempting to correct for UHI more extensively than NOAA.

The NOAA UHI correction apparently can be described as: "I'm not actually going to tell you what we do." They refer to Smith and Reynolds 2005 and I could not find any reference to UHI or any station corrections based on location.

There's a helpful UHI related summary at CO2Science.org.

I'll give you the 2 cent tour of this, as there's some interesting information. But first, I'd like to summarize a bit about UHI. Urban heat islands are the readily observable increases in temperature (both day and night) seen in cities. At night, heat absorbed in pavement and buildings can warm the city (and any NOAA temperature sensors that happen to be located there). But in the daytime, the lower albedo of cities can apparently cause warming. Wind flow is interrupted as well, probably reducing the dissipation of city heat. Finally, the heat released as energy is used (can we blame Nicolai Carnot?) is not insignificant.

So anyway, CO2 Science summarizes several papers at the location above. They point out that the UHI effect can be measured either via satellite measurements or surface thermometers. Harbor seawater temperatures show this effect as well (Boston harbor warmed 3.6°C over 100 years). He refers to a Changnon study that might show that the majority of the reported warming in Illinois from 1890 to 1950 could well be UHI errors.

In a large (~4600 residents) native community in the Arctic near Barrow, Alaska, a grid of thermometers within and well outside the community suggested that the mean UHI warming was 2.2°C and during the daytime, differences of 6°C to 8°C and above were seen.

UHI differences of 8°C have been seen in San Juan, Puerto Rico as well. The author of a study of cities in Mexico concluded that the huge magnitude of the UHI effect probably swamps any CO2 AGW signal.

The CO2 science author concludes: "it is presumptuous in the extreme to believe that the global surface air temperature record of the last few decades has been adequately adjusted for small-town and large-city heat island effects."

You might also enjoy following a blogger that has recently been plotting UHI related dataset information at: The Sextant, January 10, 2010.

7 comments:

Ira Glickstein said...

Thanks Rick for this new Topic. It is a bit more technical than normal for this Blog but of great interest to me and probably also to the flood of new visitors we have beeen attracting over the past two days from climateaudit.org, wattsupwiththat.com, and several others that picked up and reproduced my comments and graph.

I thought NOAA was part of NASA and not a separate agency. I checked and your sources are right that they are separate and that NASA-Goddard Institute for Space Studies (GISS) and NOAA-National Climatic Data Center (NCDC) publish different temperature data for the US and that the two sets have diverged by about 0.3°C (over 0.5°F).

That is about a third of the apparent global warming for the past 150 years and may lend credence to my estimate that experimental and data bias and Climategate data fudging amounts to about 30% of the apparent warming.

Urban Heat island (UHI) and other corrections are supposed to correct for known changes in the weather stations that report the raw temperature data. For example, if a given station was manually read at 8AM and 8PM for several decades, and then the time was changed to 9AM and 9PM for several decades, and then an automated system was put in to record the time and max and min daily temperatures, simply plotting the daily averages and stringing them all together would not be right. However, it is not clear to me how such a set of records from given location should or even could be properly adjusted!

Even more complex would be relocation of a given station, say from 50 years at a newspaper office to a few decades at a radio (and later TV) station building to an airport location. In the 1890's the newspaper office may have been quite rural with more horsecarts than autos in the gravel or grass parking area. The 1930's radio station may have been on or near a larger building. Over the years, the radio station may have expanded to TV, along with an asphalt paved lot and air conditioning as the years went by. That is the normal path of urbanization. The airport may have started small and then expanded around the weather station.

All of the above demands correction! But how? And by whom? Without correction, urbanization usually produces a warming trend. On the other hand, a scientist who is personally convinced that the Earth is on a warming trend that is fast approaching a "tipping point" may be motivated to save the world and human civilization by under- or over-correcting certain data to exaggerate the case and present a "nice tidy story" to motivate the politicos to act!

Ira Glickstein

PS: Authors can Edit their postings after they are published. Generally, when I edit on the first day of publication I do not indicate the change. If I edit on a later date, I will put the new text in a different color and note the date the change was made. As Administrator, I have the power to edit Topics and I have edited yours to include the proper attribution of the source of the graphic, etc. I do not have the power to edit Comments, but I can delete them. After I added the attribution for the graph to the Topic, I deleted Rick's Comment stating the attribution.

CentralCoastRick said...

Thanks for the clarifications, Ira, and for fixing the figure attribution. It's been on other sites recently (Anthony Watts, icecap.us) which is probably where I saw it first, but McIntyre appears to be the author, and my reference to GISS as 'NASA' was only because of his figure title - I should have made those clarifications myself.

For the reader that might be interested in a bit more on this, I'll add some other paper references that can be easily obtained via Google and one that may be out soon that I have great hopes for.

Apologies for taking your blog perhaps too far in one direction.

Pielke, R. A., Sr., et al. (2007), Documentation of uncertainties and biases associated with surface temperature measurement sites for climate change assessment, Bull. Am. Meteorol. Soc., 88(6), 913– 928.

Unresolved issues with the assessment of multidecadal global
land surface temperature trends, Pielke, R. A. et. al., JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, D24S08, doi:10.1029/2006JD008229, 2007

A reply to this paper from Phil Jones:

Comment on ‘‘Unresolved issues with the assessment of multidecadal
global land surface temperature trends’’ by Roger A. Pielke Sr. et al. Parker, David E., Jones, Peterson, and Kennedy; JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, D05104, doi: 10.1029/2008JD010450, 2009

And finally an informal reply (in part to the above records and to Anthony Watts' paper on NOAA station siting problems and data quality)

Talking Points related to: Is the U.S. Temperature Record Reliable?
NOAA white paper (unattributed).

The 'Talking Points' leaves me with a sticky feeling. I'm trying to shake the notion that what it really says is that if you average a bunch of bad data in with good data, it doesn't make much difference. I'm pretty weak in statistics but this jest don't sound right to this country boy. So, I'd very much like the read the following paper, should one of you find a copy. It's referenced in the 'Talking Points', seems likely to be by the same authors as the 'Talking Points' and hopefully has a lot more detail!

Menne, M. J., C. N. Williams, and M. A. Palecki (2010): On the reliability of the U.S. Surface Temperature Record, J. Geophys. Res., doi:10.1029/2009JD013094, in press. (accepted 7 January 2010)

Ira Glickstein said...

Thanks Rick again for this new Topic and for your additional info in your most recent Comment. I Googled the one about "Talking Points related to: Is the U.S. Temperature Record Reliable?
NOAA ..." and found it here. (It is always best to provide a clickable link when you know it or can find it to save others who may want to read it expecially me :^) the trouble.)

While factual, the Talking Points clearly whitewash the situation!

For example (bottom of page 2), they acknowledge http://www.surfacestations.org, run by Anthony Watts of http://wattsupwiththat.com/" and that they have surveyed 70% of the 1221 USHCN stations and say: "... they classified 70 USHCN version 2 stations as good or best (class 1 or 2). The criteria used to
make that classification is based on NOAA’s Climate Reference Network Site Handbook so the
criteria are clear."


True, but they might have pointed out that 70 good stations out of 850 surveyed is only 8% good. Therefore, over 90% are bad according to what they call clear NOAA criteria. Government bureaucrats are great at spinning the truth in ways that are not useful!

Then, they compare the average warming for the 70 good stations vs the others and plot the result. It looks pretty good until you realize the vertical scale is 4°F (-1°F to +3°F) and the differences between the sets, which seems tiny due to the overall scale, is sometimes as large as 0.4°F. On the other hand, to be fair, sometimes the 70 good stations are warmer than the others and sometimes cooler, so the net, averaged, bias is well below 0.4°F.

Please continue to comment and provide links, and I hope others read the links, provide others, and get into this discussion.

Ira Glickstein

PS: I'm with family in Pompano Beach, FL and food is calling. I'll try to read the other links later,

Ira Glickstein said...

This recently updated website from NOAA/NCDC: http://www.ncdc.noaa.gov/cmb-faq/temperature-monitoring.html explains some aspects of the sources of and correction process for raw temperature readings.

It would seem to me that worldwide development and improved technology for automatic, digitally-read thermometers would naturally increase the number of weather stations with quality instrumentation. Yet they say:

"...GHCN [Global Historical Climatology Network] has data for many thousands of stations in the period from the 1950s to the 1990s that cannot be routinely updated, thus the number of stations drops considerably in recent years. So the number of worldwide stations that are now being used has dropped off in recent years.

As for sea surface tempertures, they note "the change from ships throwing a bucket over the side, bringing some ocean water on deck, and putting a thermometer in it, to reading the thermometer in the engine coolant water intake." They have made that correction.

They also say that older readings were generally taken in the afternoon (i.e., sunset) while more recent readings have been taken in the colder mornings, so they have corrected for that.

They claim that data from rural stations compares well to urban stations.

They link to this NOAA/NCDC paper published last year by the American Meteriological Society that details the quality tests and types of corrections necessary. I read some parts of that paper and am now more confused than ever.

If Rick or someone else has the time to read and digest these papers, I would appreciate their views.

Ira Glickstein

Richard said...

In an earlier comment, I mentioned a paper I was eagerly looking forward to reading. A copy is now online of:

Menne, M. J., C. N. Williams, and M. A. Palecki (2010): On the reliability of the U.S. Surface Temperature Record, J. Geophys. Res., doi:10.1029/2009JD013094, in press. (accepted 7 January 2010)

I know I said I was eager to read it but it turns out that right now I'm much more interested in downhill and ice skating.

Ira Glickstein said...

Richard, enjoy your downhill and ice skating while the new snow lasts in central California!

Over the past week, we have seen snow in 49 of the 50 states (Hawaii is the odd man out)!

With reports of snow in Tallahassee, FL (our State capital that I have not yet visited). I thought about driving there and renting cross-country skiis for a few hours, but thought better of it! As a Florida resident for six years now, I don't like the cold, but at least it is the kind you don't have to shovel!

(My old cross-country skiis were given away when we left NY. I hope they are enjoying themselves on someone else's feet again this season. I do deep water aerobics a few days a week down here and we wear floatation and have an exercise called "cross-country" where we move hands and feet very much like real cross-country.)

Ira Glickstein

PS: It is tempting to gloat over the nationside snow and cite it as evidence Global Warming is a crock of spit. However, we all know it is mere anecdotal evidence and means little unless it becomes the norm for at least a decade or more. Weather is not climate! Even Phil Jones, the former head of the UK CRU who stepped aside as a result of Climategate, admit now that there has been no statistically significant Global Warming for 15 years, and perhaps some actual Global Cooling. We will have some warmer years in the coming decade and the Alarmists will cite that anecdotal evidence as proof human-caused Global Warming is a real threat again. Heep in mind that weather is not climate!

CentralCoastRick said...

Ira (and thousands of warmists, by which I do not mean to paint him as such) say "Weather is not Climate."

I don't really think anyone thinks it is! (Surely the weather describes the behavior that will be incrementally averaged to create the next assessment of the climate.)

My bet is that those that ask 'where did global warming go' are probably suggesting that long term records (for cold and snowfall in a large part of Northern America) must mean something (parts of Canada and the midwest are also seeing warmer than usual weather, though no heat records I've heard of).

The 'records keepers' folks seem to have taken a page out of sportscaster's book by carving 'records' into tiny pieces {The temperature at 12:01 today was warmer than it ever has been at 12:01 on any Sunday that fell on the 4th of the month for the last 26 years! (It's not that bad but many specific records still seem fairly meaningless.)}.

But I'd like to know how long it takes for a shift in weather to mean something. Many say '30 years.' - If you buy that, then why does NASA GISS smooth temperatures over 5 years and continue to announce the 'hottest year' or 'hottest decade.' Aren't they trying to have it both ways?

And the 'hockey sticks' show a steep rise for about the last 100 years - but this is very much at odds with the Central Engl reconstruction from the UK Met Office (over 300 years) and is only barely supported by the NASA GISS surface temperature (global) reconstruction.

So please ask the next 'believer' that reminds you that 'weather isn't climate' what he thinks it really means - or better yet, just ask - 'SO WHAT?'