New Paper “Climatic Trends In Major U.S. Urban Areas, 1950–2009″ By Mishra and Lettenmaier
By Dr. Roger Pielke Senior
There is a new paper
Mishra, V., and D. P. Lettenmaier (2011), Climatic trends in major U.S. urban areas, 1950–2009, Geophys. Res. Lett., 38, L16401, doi:10.1029/ 2011GL048255
which reports on the effect of urban areas on multi-decadal surface temperature trends.
The abstract reads [highlight added]
We evaluate changes in climatic indices for the 100 largest U.S. urban areas and paired surrounding non‐urban areas. During the period 1950–2009, we find that there were statistically significant changes in as many as half of the urban areas in temperature‐related indices, such as heating and cooling degree‐days and number of warm and cool nights, almost all of which are reflective of a general warming.
Similarly, statistically significant changes (mostly increases) in indices related to extreme precipitation, such as daily maximum intensities and number of days with heavy precipitation, were detected in as many of 30% of the urban areas. A paired analysis of urban and surrounding non‐urban areas suggests that most temperature‐related trends are attributable to regional climate change, rather than to local effects of urbanization, although the picture is more mixed for precipitation.
Among the conclusions
Consistent with previous studies [Easterling et al., 2000; Kalnay and Cai, 2003], trends related to temperature minima in the urban areas are generally stronger than those related to temperature maxima.
For both minimum daily temperature based climate indices and precipitation‐related trends, changes in urban and non‐urban areas are generally consistent; suggesting that the trends are dominantly a response to climate [Parker, 2004; Peterson, 2003], rather than local land cover changes during the period of analysis. However, there is somewhat less consistency in urban vs. non‐urban trends in climate indices related to daily maximum temperature, which suggests that land cover change may be at least partially responsible for those trends.
An important caveat to their study is that they have not factored in the role of microclimate changes at the observing sites which we have started to explore, as reported on in our paper
Fall, S., A. Watts, J. Nielsen-Gammon, E. Jones, D. Niyogi, J. Christy, and R.A. Pielke Sr., 2011: Analysis of the impacts of station exposure on the U.S. Historical Climatology Network temperatures and temperature trends. J. Geophys. Res., 116, D14120, doi:10.1029/2010JD015146.Copyright (2011) American Geophysical Union.
Their finding of less of an effect on minimum temperature trends on whether they are located in urban or rural areas is, however, puzzling, as the urban heat island effect on minimum temperatures is very well know (e.g. see EPA heat island effect). Since the spatial scale, density of build-up and type of constructions on urban areas continues to change over the time, the failure to find a difference between rural and urban areas needs more investigation as to why this was found in the Mishra and Lettenmaier analysis.
I think these guys must really live in their own little worlds and never think about the real one outside, in which the rest of us get in our cars on winter evenings and drive out of town, with the temperature dropping half a degree every few miles we go. How long will we have to put up with this nonsense?
And why is it apparently only children (link at top of this thread, and that 11 year old girl who did much the same kind of project) who do the oh so simple studies of rural vs city temperatures, using GISS’ own data, and find, oh wow, cities are getting hotter but the countryside isn’t?
Perhaps someone can answer whether any of the analyses of Anthony Watts’ Surfact Stations data address the quality of rural vs. urban stations. I.e.: what percent of rural stations held CRN rankings of “4” or “5”, versus the percent of similarly low-ranking stations in the urban areas.
The lowest populated areas might be one percent of the total. In any case, their specific conditions must be known.
I don’t think the Mishra research looked that carefully at their rural siting selections. Their paper makes no references to night lights, and the only criteria I can find is that their “non-urban” sites be 15 or so km outside the city, so that there would be no spillover of UHI effects there.
Mishra’s paper gives equal weight to the trends in both city and country, pairing them, then claiming that a statistically-significant trend in one is a verification of a similar trend in the other. Voila! Warming in both!
As noted by Beng (above), Spencer and others have pointed out that rural stations can be just as bad as, if not worse than, poorly sited stations in the city.
Anthony also addressed this question in the previous posting of this article (a few weeks ago).
Richard verney – the extended record should indeed be interesting, as should their sensitivity to station quality (with important contributions from Anthony Watts, apparently), UHI effects, and their apparently new statistical approach. The impression one gets from the AGU abstract is that, when all is said and done, the overall signal is similar to the other 3 products.
Very much looking forward to the details.
Bill Parsons says:
September 22, 2011 at 10:52 am
“I don’t think the Mishra research looked that carefully at their rural siting selections. Their paper makes no references to night lights, and the only criteria I can find is that their “non-urban” sites be 15 or so km outside the city, so that there would be no spillover of UHI effects there.”
How quaint. Where are these guys from, Edinburgh? Fifteen kilometers outside the city limits of Atlanta, St. Louis, Chicago, and most vibrant American cities is a new downtown more densely built than the old downtown in the city limits.
On the sea temp data history: I believe some at this site have pointed out in the past that sea captains traversing the seas have kept daily logs, including meteorologic data, for centuries.
Though creating a useful data base out of these logs might be hard work, time consuming, and expensive, the consequences of government decisions re CAGW are so great, that funding for such tedious research ought to be readily available.
Sorry.. their “band” of separation between urban and “non-urban” was 25 km, not 15. I was thinking of miles.
I still think they should have selected 4’s and 5’s from the Surface Station “approved” sites. Any studies which deliberately ignore Watts’ research do so at their own peril.
Bill Parsons says:
September 22, 2011 at 12:48 pm
“Sorry.. their “band” of separation between urban and “non-urban” was 25 km, not 15. I was thinking of miles.”
Won’t matter much. Fifteen miles north of the Atlanta city limits is still downtown Atlanta.
What we need are scientists who have instincts for the empirical. Scientists who respect the authority of actual observations of reality. Instead, we have a bunch of self-taught wannabe statisticians who are interested only in trends and never in empirical observation. In fact, they are repulsed by empirical observations. In the last couple of months on this site, Mosher did an informal statistical analysis of a temperature station at an airport near San Francisco. The station was interesting because it was reading 4 degrees higher than nearby stations. Mosher’s analysis made all 4 of those degrees go away. My response to such analysis is “Thank You, Sir, for exhibiting your great skill at hiding the pea.”
I see a trend in “science”, especially “climate science”, especially among the pro AGW crowd, to what can only be called white collar science. Basically, instead of actually doing anything themselves, getting their hands dirty with actual experiments and gathering real data and finding out what the actual local conditions are (so they can factor those in), they instead stay in their nice cozy bureaucratic office environment and play with statistics from other peoples data. This is what they know, from their ivory tower existence inside universities, where they never have to be in contact with reality, but can instead only concern themselves with the theoretical rather than ever getting their hands dirty with, say, raw nature.
If they ever got out of that nice comfey air conditioned office environment, they would know that cities are hot and the country is cool. I doubt that many of them ever even leave the city, some may never have. They are basically like the new ruling liberal elite, the noble lords who live in the castle, while only the peasants live out in the fields and country. Like nobles, they don’t want to get their hands dirty with real work and leave their comfey academic environment (except for an occasional junket to exotic vacation spots called climate conferences). They also hang out only with their own kind, and thus may never even hear that anyone has a different opinion than what is the current peer pressure enforced (and grant money reinforced) local academic one. In short, they live in their own little world.
Thus we have this study, yet another playing with statistics of other peoples data, about which the players actually know little about, such as what the local conditions are or how it was gathered. As such, it is virtually irrelevant to the real world. Not that these people care, they don’t live in that world.
Where was that photo taken?
People will always look for the next new thing. Today it’s content; yesterday, it was social media