New study shows how local land use changes can affect surface temperature

Study gives clearer picture of how land-use changes affect U.S. climate

from a Purdue University press release

land-use-graphic

This map shows observation minus reanalysis (OMR) trends in the continental United States from 1979-2003. The trends are associated with land use and land-use changes. Researchers from Purdue and the universities of Colorado and Maryland conducted a study that showed land use can affect surface temperatures locally and regionally. Units are in degrees Celsius per decade. (Image courtesy of Souleymane Fall) - click to enlarge

Researchers say regional surface temperatures can be affected by land use, suggesting that local and regional strategies, such as creating green spaces and buffer zones in and around urban areas, could be a tool in addressing climate change.

A study by researchers from Purdue University and the universities of Colorado and Maryland concluded that greener land cover contributes to cooler temperatures, and almost any other change leads to warmer temperatures. The study, published on line and set to appear in the Royal Meteorological Society’s International Journal of Climatology later this year, is further evidence that land use should be better incorporated into computer models projecting future climate conditions, said Purdue doctoral student Souleymane Fall, the article’s lead author.

“What we highlight here is that a significant trend, particularly the warming trend in terms of temperatures, can also be partially explained by land-use change,” said Dev Niyogi, a Purdue earth and atmospheric sciences and agronomy professor, and the Indiana state climatologist. He is the study’s corresponding author.

Niyogi and Fall say the idea that land use helps drive climate change has been poorly understood compared to factors such as greenhouse gas emissions. But that is changing.

“People realize that land use cover also is an important force and not only at the local but also at the regional scale,” said Fall, whose doctoral research focuses on the impacts of land surface properties on near-surface temperature trends.

The researchers used higher resolution temperature data than previous studies, meaning the data was more detailed, Niyogi said. They also employed dynamic data on land-use changes from 1992-2001, which was derived from satellite imagery.

Niyogi said having an understanding of land use’s affects on climate change could have climatic and other benefits. For instance, creating green spaces and buffer zones in and around urban areas also could be aesthetically attractive, he said.

Among the study’s findings:

* In general, the greener the land cover, the cooler is surface temperature.

* Conversion to agriculture results in cooling, while conversion from agriculture generally results in warming.

* Deforestation generally results in warming, with the exception of a shift from forest to agriculture. No clear picture emerged from the impact of planting or seeding new forests.

* Urbanization and conversion to bare soils have the largest warming impacts.

In general, land use conversion often results in more warming than cooling.

The study took an approach called “observation minus reanalysis,” or OMR. Through this process, the researchers used temperature data from local ground observations, observation and computer modeling, Geographic Information Systems (GIS) and statistical methods. They were able to separate the effects of land use or cover from greenhouse warming and isolate the impact from each land use or cover type. The more detailed data provided a clearer picture of the effects of land surface properties on near-surface temperature trends.

“We showed this quantitatively for the first time,” said University of Maryland atmospheric and oceanic science Professor Eugenia Kalnay, who developed the OMR method with Florida State University Professor Ming Cai. She also is a co-author of the study.

While the effects of greenhouses gases like carbon dioxide are clear, Kalnay said, the study does suggest land use needs to be considered carefully as well.

“I think that greenhouse warming is incredibly important, but land use should not be neglected,” she said. “It contributes to warming, especially in urban and desertic areas.”

Another study co-author, Roger Pielke Sr., said the results indicate that “unless these landscape effects are properly considered, the role of greenhouse warming in increasing surface temperatures will be significantly overstated.” Pielke is a senior research scientist in atmospheric and oceanic sciences at the Cooperative Institute for Research in Environmental Sciences and the Department of Atmospheric and Oceanic Sciences at the University of Colorado in Boulder.

Purdue’s Gilbert Rochon and Alexander Gluhovsky also participated in the study. Rochon is associate vice president for collaborative research for Information Technology at Purdue (ITaP) and director of ITaP’s Purdue Terrestrial Observatory satellite and remote sensing data program. Gluhovsky is a Purdue professor in earth and atmospheric sciences and statistics.

The work was supported by the U.S. Department of Energy Atmospheric Radiation Measurement program, NASA, the National Science Foundation, and the National Oceanic and Atmospheric Administration.

###

ABSTRACT

Impact of land use cover on temperature trends over the continental United States: assessment using the North American Regional Reanalysis

We investigate the sensitivity of surface temperature trends to land use land cover change (LULC) over the conterminous United States (CONUS) using the observation minus reanalysis (OMR) approach. We estimated the OMR trends for the 1979-2003 period from the U.S. Historical Climate Network (USHCN), and the NCEP-NCAR North American Regional Reanalysis (NARR). We used a new mean square differences (MSDs)-based assessment for the comparisons between temperature anomalies from observations and interpolated reanalysis data. Trends of monthly mean temperature anomalies show a strong agreement, especially between adjusted USHCN and NARR (r = 0.9 on average) and demonstrate that NARR captures the climate variability at different time scales. OMR trend results suggest that, unlike findings from studies based on the global reanalysis (NCEP/NCAR reanalysis), NARR often has a larger warming trend than adjusted observations (on average, 0.28 and 0.27 °C/decade respectively).

OMR trends were found to be sensitive to land cover types. We analyzed decadal OMR trends as a function of land types using the Advanced Very High Resolution Radiometer (AVHRR) and new National Land Cover Database (NLCD) 1992-2001 Retrofit Land Cover Change. The magnitude of OMR trends obtained from the NLDC is larger than the one derived from the static AVHRR. Moreover, land use conversion often results in more warming than cooling.

Overall, our results confirm the robustness of the OMR method for detecting non-climatic changes at the station level, evaluating the impacts of adjustments performed on raw observations, and most importantly, providing a quantitative estimate of additional warming trends associated with LULC changes at local and regional scales. As most of the warming trends that we identify can be explained on the basis of LULC changes, we suggest that in addition to considering the greenhouse gases-driven radiative forcings, multi-decadal and longer climate models simulations must further include LULC changes.

The peer reviewed paper which this press release discusses is

Fall, S., D. Niyogi, A. Gluhovsky, R. A. Pielke Sr., E. Kalnay, and G. Rochon, 2009: Impacts of land use land cover on temperature trends over the continental United States: Assessment using the North American Regional Reanalysis. Int. J. Climatol., DOI: 10.1002/joc.1996.

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78 thoughts on “New study shows how local land use changes can affect surface temperature

  1. WattsUpWithThat also featured a land use study done by Morton D. Winsberg of Florida State University.
    “With little or no land use change, Winsberg says, areas showing a longer hot season would have followed the general cooling trend seen elsewhere in the Southeast U.S.”
    http://wattsupwiththat.com/2009/02/10/floridatrend-its-hot-but-dont-blame-global-warming/
    The case for co2 as the controlling factor in weather and climate grows weaker. I have not seen any evidence strengthening it. It’s end is inevitable.

  2. “A study by researchers from Purdue University and the universities of Colorado and Maryland concluded that greener land cover contributes to cooler temperatures, and almost any other change leads to warmer temperatures.”
    Umm… plant more trees then… it might soak up some of that (so called ) excess CO2 then… SHEESH!!!

  3. Minor quibble, but the map depicts a swath of the North Cascades in WA as warming. This may be true, but as a Nat’l Park it is not due to conversion. It’s also possible the map scale is a bit off. But that northwest WA red are is prime agricultural land butting up to National Forest and State forest land butting up to Nat’l Park. Looks suspicious.
    Back when forest management was a respectable course of study the general conclusion in the West was that soil surface temps on a south facing slope could reach over 140F on a sunny spring day.

  4. Without disputing anything, isn’t albedo the be all and end all of temperature correlation? A dark green forest or cornfield will have a low albedo, but perhaps not as low as dirt. Are there any uses which would increase albedo? Hockey rinks? White pavement and roofs? An icefield or glacier?

  5. “I think that greenhouse warming is incredibly important, but land use should not be neglected,” she said. “It contributes to warming, especially in urban and desertic areas.”
    The only thing that is important about “greenhouse warming” is the damage to the global economy the eco-fascists will cause whilst allegedly combatting it.
    But this new study is another lttle straw in the wind showing that CO2 ain’t guilty.

  6. “Among the study’s findings: * In general, the greener the land cover, the cooler is surface temperature.”
    Some maple trees are highly regarded and widely planted in urban landscapes and some, an example is the purple leaf Norway maple, have non-green leaves, even in summer. On the other hand, things can be painted green. I wonder if by the phrase “the greener the land cover” they really mean ‘the color green’ or living things that have green colors, or just plants? Would plants with very light colored leaves be the best? Or is it the evapotranspiration process that is the thing to focus on?
    Should any plant that has non-green leaves be banned from landscape plantings and sought-out and destroyed in its natural habitat. Should our roofs be colored green or white?
    The thing that bothers me about this report is their assumption that greenhouse warming is an established thing — “They were able to separate the effects of land use or cover from greenhouse warming and …”
    I wonder if they have read any of the “how not to measure temperature” postings?

  7. Terry Jackson (22:59:01) : re: northern Washington State
    I missed this until reading your comment. From 1979 to 2003 I wonder what land cover change could have been contributing to this? I’ve helped widen a few hiking trails, including parts of the PCT in this region. Not much else going on that I noticed!

  8. Slightly O/T. Initially I was searching for ‘coldest october on record’. Now I had found over 100 cities in the U.S. breaking records or near records for coldest temp or snowiest month or record rainfall for october, I also found parts of the U.K. was also experiencing the same thing and N. Z. as well.
    But then I stumbled across this little gem.
    CLIMATE CHANGE: Temperature readings in rural Australia show no increase in 100 years
    by Dr A.L. McClintock
    “Weather observatories in Australia, dating back 100 years or more, show cities getting hotter as they get bigger; but country towns have generally not been warming up. Some have actually been cooling down.”
    http://www.newsweekly.com.au/articles/2009oct31_c.html
    I’m sure (someone) will post about Oct. Temps. , so I’ll leave that alone for now, because this article was a eye-grabber.
    It has been my understanding that UHI effect has been largely overlooked by the I.P.C.C. and the UK Met Office because of their alarmist views on AGW. I can understand why now. I don’t know about the rest of you, but I want to dump 1000 copies of this article on a little known office ran by P. Jones.
    Then stand out in the parking lot and use a line from an old sitcom, ” Oh Lucy! You have some esplaynin to do!”

  9. martin brumby (23:07:09) : ” … The only thing that is important about “greenhouse warming” is the damage to the global economy the eco-fascists will cause whilst allegedly combatting it.”
    Some nice support for this comment, Martin can be found here: Placing My Lance – George Rebane

    Promoting AGW and its proposed fixes rests on three legs – the science, the economics, and the geo-politics. If the mind of the masses is to be illuminated, we have also to bring up on everyone’s radar the perfidy behind economic and ideological ‘solutions’.

  10. Among the study’s findings:
    * In general, the greener the land cover, the cooler is surface temperature.
    * Conversion to agriculture results in cooling, while conversion from agriculture generally results in warming.
    * Deforestation generally results in warming, with the exception of a shift from forest to agriculture. No clear picture emerged from the impact of planting or seeding new forests.
    * Urbanization and conversion to bare soils have the largest warming impacts.
    In general, land use conversion often results in more warming than cooling.

    Like…um…DUH???

  11. I am quite surprised that agricultural land changes lead to cooling. Bare soil is darker and absorbs sun radiation better, warming the air above (everyone who flies gliders knows it). Another case is, when swamps are turned to fields, which has definitely warming effect.
    I am also curious, how the authors “separated the effects of land use or cover from greenhouse warming”, since US experiences free fall in temperatures since 2005.

  12. Terry Jackson (22:59:01) :
    Minor quibble, but the map depicts a swath of the North Cascades in WA as warming.
    The map covers trend from 1979 – 2003. I don’t have the charts of +/- PDO in front of me but if I am remembering correctly there was a +PDO during most, if not all, of that time frame. The effects of a +PDO could be the explanation since Washington is next to the Pacific.

  13. On a trip to Borneo a few years ago I noticed that night temperatures in the inland were far more acceptable than on the coast i.e. cooler. This was despite being away from coastal breezes, surrounded by jungle and no more than 200 ft above sea level. All I could put it down to was the evapotranspiration from the rainforest and the higher rainfall in these forest areas. Every afternoon it used to pour down with rain from towering cumulonimbus clouds, no doubt the rain drops were cooled from their formation high in the clouds. I get the impression that vegetation is an even better airconditioner than the ocean.

  14. OT, but relevant?
    Pielke Jnr has thrown down the glove.
    http://rogerpielkejr.blogspot.com/2009/11/open-invitation.html
    This Blog
    This Blog
    02 November 2009
    Open Invitation
    Here is an open invitation to my loudest critics. I’d like to invite Joe Romm, Tim Lambert, the guys at Real Climate, William Connolley and anyone else (apologies to critics not mentioned, no slight intended;-) to engage in a substantive debate on the following 10 conclusions that I’ve reached about the climate issue, based on the fact that the human influence on climate is real, serious and deserving of significant policy attention:
    1. There is no greenhouse gas signal in the economic or human toll record of disasters.
    2. The IPCC has dramatically underestimated the scale of the stabilization challenge.
    3. Geoengineering via stratospheric injection or marine cloud whitening is a bad idea.
    4. Air capture research is a very good idea.
    5. Adaptation is very important and not a trade off with mitigation.
    6. Current mitigation policies, at national and international levels, are inevitably doomed to fail.
    7. An alternative approach to mitigation from that of the FCCC has better prospects for success.
    8. Current technologies are not sufficient to reach mitigation goals.
    9. In their political enthusiasm, some leading scientists have behaved badly.
    10. Leading scientific assessments have botched major issues (like disasters).
    Here is my guarantee:
    Your comments will be allowed here in full, they will not be deleted or snipped. I will delete comments that are off topic much more rigorously than I usually do to keep a clear focus. Anyone can participate, but I will require respectful, substantive discussion at all times. If there is enough interest, I will be happy to spin off unique threads for any of the 10 topics that people want to challenge or debate.
    OK guys here is your chance to step up and show the world where I am wrong based on a substantive discussion of issues that really matter. What do you say? All are welcome.
    I think my money’s safe, if I popped into the Bookies & wagered that none of his aforementioned critics will engage in the discussion.

  15. David Alan (00:04:46) :
    🙂 A POI.
    The Met Office only overlook things when convenient to do so. As Prof John Brignall has pointed out on Number Watch before, Dr Vicki Pope has advised in national newspapers that the UHI will (could/might/may/possibly/potentially/likely) kill 100s by 2100 due to global warming, whereas the likes of Dr Jones (no not hunky heroic Harrison) has implied that the UHI is insignificant & has been accounted for & doesn’t affect the evidence supporting Global Warming!

  16. The phrase ‘reinventing the wheel’ comes to mind.
    All this was known 50 years or more ago but no one bothered to quantify the effect because it was taken as a given and, moreover, a factor that was too complex to quantify adequately at that time. The best that could be done was to apply very rigorous site standards, so rigorous that I abandoned all hope of contributing to the recording system of the day. As Anthony has proved, those standards were then abandoned wholesale.
    It seems that so many AGW proponents have so little real world knowledge that they piled into a wholly speculative and unlikely scenario and in the course of rowing back from it they are now ‘discovering’ stuff that they should have known from their schooldays.
    Another area where I find total incomprehension amongst warmlings is the issue of latent heat.
    They are genuinely unaware that evaporation has a net cooling effect. I find so many otherwise well informed warmlings insisting that either the process is temperature neutral or that the extra evaporation induced by downward re-radiated infra red energy leaves an energy residue available for warming of the environment.
    The more I have looked into this over the past 18 months the more I have found the problem to be that warmlings focus on large numbers of individual bits of data and extrapolate madly from them yet have no idea how the climate system works as a coherent whole so that the proper weighting is never attributed to those bits of data.
    I suspect that all the models are similarly replete with nonsensical weightings due to such issues.

  17. Conclusion: Land change use introduces a bias in the surface temperature record.
    Green: Cool
    Tar Macadam: Warm
    Doesn’t this study confirm what most all ready knew?

  18. Roger Carr (00:16:29) :
    They will not only damage the economy, they will damage the Climate and the ability of civilization to adapt to the natural cycles of change.
    What drives the madness?
    Power?
    What power can one have if one brings down their own country?
    Monetary gain?
    What profit can one make if one destroys the very currency accumulated?
    Eden?
    What garden will one have if the aim is to remove from the Earth all the carbon upon which terrestrial life is based?
    But today:
    http://www.foxnews.com/politics/2009/11/03/gop-senators-talk-boycotting-climate/%20/?test=latestnews
    GOP Senators talk of Boycotting Climate Bill.

  19. Logic. If some land is classed as an unfarmed sand desert, how does this affect the temperature? Presumably, if it has been a sand desert for some centuries, it is more or less in equilibrium and it is not going to produce a trend today that can be substracted from another trend like proposed GHG.
    While closely settled countries with active land use changes might show a signal, places like the Antarctic and much of Australia and Africa have insignificant land use changes of a type that would need accounting in the energy balance. In any case it would need to tie in with albedo changes for the whole earth.
    Besides, the sea dominates the heat equations. Not the NH, not the USA.

  20. “Simon Filiatrault (02:09:43) :
    Another related study about land use vs energy sources used I document on my blog
    http://tr.im/DTUg
    The more “green” you are the more land you use!”
    I agree with this. All the “greenie” types stating that we grow our own food blah blah blah, lmao, I live in an apartment block (Ever growing “solution” in Australia), where can I grow food, generate power etc etc (Strata bylaw restrictions etc etc)? If I had access to 1 acre block of land within commuting distance to work, I’d need to be wealthier than Al Gore (Thanks to oil for him and soon carbon credits).

  21. Correction..
    “I live in an apartment block (Ever growing “solution” in Australia), where can I grow food, generate power etc etc”
    Should read..
    “I live in an apartment block (Ever growing “solution” in Australia), where *can’t* I grow food, generate power etc etc”

  22. As an architect I need to design with passive solar design principles, such as orientation, heat sinks, wall and roof colour etc. Yet when it comes to the heat island effect on temperatures we are meant to ignore it. So we have a situation where basic solar design principles are required in design to control the temperature of a building but not in recording the temperature.

  23. @Stephen Wilde (02:43:57) “The phrase reinventing the wheel comes to mind.” Indeed it does, in the course of reading nearly every study, or more precisely, the media take on nearly every study, seen on this blog. Often it’s not just the journalist who hadn’t heard of that before, it’s also the researchers.
    With regard to the map accompanying this blog; are the colors reversed? Or are the blues in previously high density areas which just did not change (or got cooler?) in the years covered by the study. Did the southern California desert cool due to land use changes between 1979 and 2003?
    What land use changes other than forest fire occurred in the Bitterroot Mountains of east central Idaho and southern Montana? Most of this land is national forest and much of it that is not forested is grassland.
    The article is behind a pay wall.

  24. OT, but I thought you might all like this:
    http://news.bbc.co.uk/1/hi/england/oxfordshire/8339652.stm
    “After the hearing, his solicitor, Shah Qureshi, said: “Essentially what the judgment says is that a belief in man-made climate change and the alleged resulting moral imperative is capable of being a philosophical belief and is therefore protected by the 2003 religion or belief regulations.”
    Yes, AGW is a religion, I always knew it was!

  25. The press release (but not the abstract) confuses climate warming with increased (atmospheric) temperatures.
    Deforestation generally results in warming
    Deforestation results in warmer temperatures. However, this is because forests absorb more solar energy. That is forests result in heat gain to the Earth’s climate system. Remove the forests and some of that heat enters the atmosphere giving warmer atmospheric temperatures. It also of course means that heat will be lost to space, cooling the climate.

  26. Stephen Wilde (02:43:57) :
    It seems that so many AGW proponents have so little real world knowledge that they piled into a wholly speculative and unlikely scenario and in the course of rowing back from it they are now ‘discovering’ stuff that they should have known from their schooldays.

    Mac (02:49:15) :
    Conclusion: Land change use introduces a bias in the surface temperature record.
    Green: Cool
    Tar Macadam: Warm
    Doesn’t this study confirm what most all ready knew?
    Hence my earlier: “Like…um…DUH?” comment. 🙂
    Geeks who spend all their time in academia and computerland are clueless about the real world. These “self evident” truths about the natural world escape them.

  27. OT: British courts recognise belief in AGW as a religion.
    See this from the bbc.

    After the hearing, his solicitor, Shah Qureshi, said: “Essentially what the judgment says is that a belief in man-made climate change and the alleged resulting moral imperative is capable of being a philosophical belief and is therefore protected by the 2003 religion or belief regulations.”

  28. I suppose I should repeat what I have said before. I live in rural Devon, 15-20 minutes outside the provincial city of Exeter. In the winter evenings, I drive my car out of the driveway, aircon says -3°C. After a few minutes up over the hill & down the other side, aircon reads -2°C. As I approach the outskirts of the city, aircon reads -1°C. In the city centre, aircon reads +1°C. It appears to be the reverse when I return home for some peculiar reason I cannot fathom. Curiously it happens in the summer months too, but a few degrees higher up the scale, (although not the last 3 summers). Not scientific, Peugeot’s electronics may not be the most accurate but the error would be consistent more or less, but it illustrates the point I feel!
    How much do these guys get paid for “discovering” all this stuff? I think I need to apply for a research grant as the pension plan looks a little shakey.

  29. The study is flawed. There is no consideration or mention of the UHI effect putting a warm bias into the temperature record. About all we are really affecting are localized temperatures, not climate.
    This is just one more example of agenda-based “science” : creating green spaces and buffer zones in and around urban areas, could be a tool in addressing climate change. How absurd. Sure, they’d be nice to have. But, so would a lot of things.
    Until it’s time to try to come up with the money to pay for them.

  30. In Glasgow, Scotland, the clans bequeathed land they owned to the city so that the people of that city – including many “emigrants” of their own – could enjoy it. Seems a better reason than spurious science.

  31. A tree is just a giant “mister.” It’s sucking tons of cool subsurface water up, and expelling it into the atmosphere.
    Ask any little kid why he sits up in the tree in the summertime. It’s cooler up there. And, trust me; it’s cooler up in the oak tree than it is in the sweet corn patch.

  32. Until I can read the entire article, I call this one junk. The red bands correspond to exactly what is expected under El Nino conditions, IE the Pacific was in a warm phase. On top of that, I can tell you that the NE corner of Oregon is not exactly what I would call a den of development. If anything can be said, it would be that high desert was turned into green crop circles. Yet the temps remained high. My hunch is that if I were the peer reviewer I would have ripped this article to shreds and recommended it be round filed.
    REPLY: The paper is linked below the main article. – Anthony

  33. @Terry Jackson The albedo is not the full story. A cornfield may have a low albedo but it uses up a lot of energy in the latent heat of evaporation from the plants.

  34. “I am quite surprised that agricultural land changes lead to cooling.”
    Wouldn’t this depend, among other variables, upon latitude and the prevalence of unbroken winter snow cover, and the consequent change in albedo?
    New Jersey, for example, the most densely populated state in the U.S., has significantly more tree-cover than it did a century ago–or even fifty years ago– as suburban development has gobbled up farmland, with consequent planting of trees on what used to be cleared fields.

  35. @Alan the Brit In NYC when I was growing up in the 50s, the local temperatures were reported from lower Manhatten. We lived maybe 10 miles away in NJ. The normal adjustment was of the order of 6 degrees F.

  36. We already know what causes climate change and all this “denier” science is designed to purposely confuse the issue. How much oil money funded this study?
    Oh, I forgot to mention big tobacco. How much did big tobacco pay for this study? Did the authors take money from big insurance companies?
    BTW: This is sarcasm.

  37. For some unknown reason a vision came to mind. Kinda deja vouish, y’know? It’s 2010, we’re flies on the wall in the Oval Office: “Here it is again! Proof positive! As the wierdo Trekees say: ‘It’s all the fault of the Carbon Units infesting planet Earth.’ Wonder what the effect would be of reducing US population levels to those of 1941 (and, of course, the size of the concrete footprints of NYC, LA, Chi-town, Seattle, Philly, etc., etc.). No one wants to face the ugly truth, it’s NOT CO2, it’s over-population. But you know how things are today, it’s not something you can say out loud like a good four letter word, you have to be sensitive to people’s feelings.” When the WH Chief of Staff finished talking, everyone nodded quickly in agreement. (He had a very bad temper. Y’know?)

  38. Doug in Seattle (00:13:44) :
    I’m not sure the map goes where the press release leads.
    ——-
    Comparing the map with the Google map, I’d agree. Why no large splotches of dark red in Texas? Why are the large, dark red splotches (CA, WA, CO) in national parks? What land use changes at the Canadian border in MN caused the small splotch of large temp difference?
    And from impressions of what’s gone on with land use changes since 1979, shouldn’t there some indication of a bluing in the SE Michigan area at least similar to what is represented in the Buffalo, NY area? Shouldn’t there be more red in FL especially along the Gulf coast?
    Does the map only reflect the 1992-2001 land-use changes or did they also take advantage of the plethora of aerial photography that’s been done since 1960 in relation to municipal planning but it is just not mentioned in the Press Release? The 1992-2001 window of land use change seems awfully small to be using to establish a pattern with the preciseness of the temperature changes shown in the legend, especially if it is to also remove natural temperature variations as a contributing variable.
    But those concerns aside (and maybe I misread the objective of the work), I can appreciate the effort to establish a rational method for measuring the degree to which land use changes affect surface temperatures to substitute for the memories of those who grew up in cities during the end of the American Elm Era and can tell you how much of a affect trees covering city neighborhoods make to urban temperatures.

  39. Question the data. I suppose that these longish term trends come from surface measurements. surfacestations.org shows exactly how small modifications around a temp probe can change the data for a local area, or region.
    If these affects were removed, I suspect there would not be wide spread red regions on the map – just little pin points.

  40. “greener land is cooler”? Who wouldda thunk? My granddad (long since passed away) could have told them that. How much taxpayer dollars did they spend ‘discovering’ what our ancestors have known for millennia?

  41. OT but science related 🙂
    Some of you may have recently heard that a chairman of the UK’s Advisory Council on the Misuse of Drugs was sacked by our esteemed (allegedly) Home Secretary due to a difference of opinion that doesn’t warrant identification here. Much embarrassment & anger has risen to the surface (all jolly exciting I must say). However, the interesting point is that Professor Nutt has been most vocal about high quality science & the scientific evidence as opposed to government policy decisions, in this case related to canabis use. The UK’s Chief Scientist has also weighed in about such things & the requirement for government to have top quality science advice provided to it at all times. It will be equally interesting to see if anybody raises the obvious question about AGW & CC! Somehow I think not.

  42. This is just one more example of agenda-based “science” : creating green spaces and buffer zones in and around urban areas, could be a tool in addressing climate change. How absurd. Sure, they’d be nice to have. But, so would a lot of things.
    Until it’s time to try to come up with the money to pay for them.” Bruce Cobb
    Actually this is a real boon for farmers in the USA. When the new food safety regs go into effect making growing food too cost prohibitive we can switch to growing trees and being paid by corporate carbon offset dollars.
    Now I just have to figure out the marketing and ways around the regulations so I can feed at the public trough too….
    Oh yeah I hope you like to eat dead tree leaves since the USA used to grow 25% of the worlds food supply.

  43. I think this type of study must be considered before we convert 10-20% of the desert southwest into a mirror or other solar collector surface. These large solar farms that have been proposed could have a large regional impact on climate. I have wondered if the removal of such a large amount of solar heating in this area will result in lower nighttime temperatures and what impact that has on local wildlife survival in winter months. Although the solar heating that is being intercepted by the solar farms is small, I would expect the effect to be non-zero and somewhat cumulative over time.

  44. I believe that land use change is the major climate warming vehicle and the larger environmental threat; however, I fail to see how the posted map makes the case.
    The areas of Colorado, Utah, Wyoming, and Idaho that show the greatest temperature increases have had little development or land use change. If anything, the BLM leases on public lands have reduced grazing pressures.
    The rapidly growing urban areas of Florida and Texas generally show no significant change. Although Minneapolis and Boston show increases, the much faster growing areas of Northern Virginia and Oklahoma City show declines. Coastal Southern California shows a small increase, but the Antelope Valley, an area of massive land use change in the past two decades, shows a significant decline.
    To repeat, although I believe that land use change is key to warming – this map doesn’t seem to make much of a case.

  45. The Dust Bowl disaster in Mid-Western States in the 1930’s and 1940’s was the direct result of a change in land use. The hitherto robust grassland, which had been capable of withstanding extended periods of drought, was replaced by crops which did not have this resistance. Consequently, long periods of dry weather caused the crops to wither and die, and the topsoil was then no longer secured. It blew off as fine dust, causing choking black storms. The weather for the whole region was substantially modified, and the drought became even more extended as a result.
    The whole process started with a government initiative to provide free land for farmers and encourage change of land use for productive farming.
    This well-documented event demonstrates clearly that man can indeed modify local climate to a very significant extent, and emphasises that change of land use is a key component in this process.
    In the UK, while the government is proposing to adopt draconian measures to cut CO2, it continues to encroach on substantial areas of green land for housing development, while leaving old industrial city areas barren wasteland.

  46. Gail Combs says:

    Oh yeah I hope you like to eat dead tree leaves since the USA used to grow 25% of the worlds food supply.

    If growing seasons are affected by “climate change” (and by climate change I mean cooling) then it might still do so (except in California where there will be no water allotted to the Central Valley). However, overall, less food will be grown.
    Hold on to your hats. Interesting time ahead.

  47. Finally!
    IMO, climate natural variability + sun radiation change + land use change = 100% temperature change.
    The cycle of water eats huge amount of sun energy when water is changed into vapor. I think it is something like half a year of sun radiation stored in water cycle.
    Deplete the cycle of water and this sun energy has to go somewhere else…heat. And we all can see rivers levels have been decreasing because of land use change, this is a well known fact -> land use change may have a very underestimated influence on temperature.
    It’s not only a simple question of albedo…land use change has a long chain of consequences sorry for poor english.

  48. You would think a forest fire and the resulting blackened earth left behind would be an extreme case of land surface change effecting temps.

  49. @Alan the Brit
    The Professor Nutt escapade is quite amusing – not least because both the existing Home Secretary Alan Johnson and his predecessor Jacqui Smith (not to mention Brown) both obviously reckoned that they should be able to expect scientific experts to provide backing for whatever fashionable soundbyte they thought would play best with the press and the sheeple.
    But there is a difference with AGW. Here both this Government and previous governments for at least 20 years have been avidly stuffing hard line eco fascist AGW worshippers into every possible key “scientific” advisor position. Robert Napier, David McKay, Lord Stern, Lord Turner, David King. The list goes on and on. Plus they have used backdoor influence to make sure that the management boards of NGOs, charities and Scientific Institutions, even the Royal Society are packed with ‘reliable’ people.
    Consequently, what kind of “scientific advice” do you think they receive?
    A bit like the old fable of the parish church clock which always agreed with the time the village watchmaker showed in his shop window. Every morning when the church warden went to work he set his watch by the clock in the watchmaker’s window, then adjusted the church clock when he arrived. And every lunchtime, the watchmaker set the clock in his window when the parish church clock started to chime.

  50. “Terry Jackson (23:04:50) :
    Without disputing anything, isn’t albedo the be all and end all of temperature correlation?”
    Albedo is a huge factor, but plants (green or otherwise) which use energy in photosynthesis, soak up and convert the energy into growth, so it’s not available to warm the local climate (until it burns or decomposes). And plants release water into the atmosphere, through evapotranspiration, which cools the local climate.

  51. If not to “address climate change”, because unless you change the Length of the Day you won’t change anything, at least having parks it’s beautiful. They will be colder as we enter the new Maunder like minimum, but nice anyway.

  52. Juraj V. (00:50:16) :
    “I am quite surprised that agricultural land changes lead to cooling. ”
    Trees reduce wind flow and thus forests will be warmer than open fields due to higher wind chill and evaporation in open fields.

  53. More about land cover change to weather/climate can be found in “Impact of land cover change on the climate of southwest Western Australia”, (Pitman, Narisma, Pielke Snr, Holbrook, 2004).
    http://www.waclimate.net/land-clearing.pdf (580kb)
    Extract: “We explore an alternative hypothesis that large-scale land cover change explains the observed changes in rainfall and temperature. We use three high-resolution mesoscale model configurations forced at the boundaries to simulate (for each model) five July climates for each of natural and current land cover. We find that land cover change explains up to 50% of the observed warming. Following land cover change, we also find, in every simulation, a reduction in rainfall over southwest Western Australia and an increase in rainfall inland that matches the observations well. We show that the reduced surface roughness following land cover change largely explains the simulated changes in rainfall by increasing moisture divergence over southwest Western Australia and increasing moisture convergence inland. Increased horizontal wind magnitudes and suppressed vertical velocities over southwest Western Australia reduce the likelihood of precipitation. Inland, moisture convergence and increased vertical velocities lead to an increase in rainfall.
    … Since we are simulating isolated months (July) we cannot capture trends in soil moisture associated with drying in June, and we therefore probably underestimate the large-scale impact of LCC on the latent heat flux and temperature.”

    Temperature data from the 1800s to now (http://www.waclimate.net) suggests a cooling in some towns within the area of southwest Western Australia cleared for agriculture. Averaging temps from the available 32 locations across Western Australia with 100+ year records, the state’s maximum has increased by .6 degrees C and its minimum has increased by 3.9 degrees C when comparing the early 20th C average to the 12 months up to and including October 2009.

  54. AManuel (08:32:14) :
    “I think this type of study must be considered before we convert 10-20% of the desert southwest into a mirror or other solar collector surface. These large solar farms that have been proposed could have a large regional impact on climate. ”
    As a new resident of Burbank, I’m looking forward to cooler climate in the Mojave keeping the Santa Ana winds blowing cool air downhill for more of the year. Maybe it will help with precipitation as well…

  55. Goreacle Report: Al moves on.
    Gore tosses CO2 into the ash heap of his history:
    “”Over the years I have been among those who focused most of all on CO2, and I think that’s still justified,” he told the magazine. “But a comprehensive plan to solve the climate crisis has to widen the focus to encompass strategies for all” of the greenhouse culprits identified in the Nasa study.”
    “Gore acknowledged to Newsweek that the findings could complicate efforts to build a political consensus around the need to limit carbon emissions.”
    …-
    “”He is one of the only politicians that takes the time to actually talk to scientists who are producing the cutting-edge stuff and he comes in with questions. He doesn’t ask us how our results impinge on a particular policy he actually asks about science,” said Gavin Schmidt, a climatologist at Nasa’s Goddard Institute for Space Studies, who spoke to Gore along with colleagues four or five times for the book.
    >>> “Nobody that we have dealt with has ever taken as much time to understand the subtlety of the science and all the different complications and what it all means as Al Gore.”
    Those conversations led Gore to politically inconvenient conclusions in this new book. In his conversations with Schmidt and other colleagues at the beginning of the year, Gore explored new studies – published only last week – that show methane and black carbon or soot had a far greater impact on global warming than previously thought. Carbon dioxide – while the focus of the politics of climate change – produces around 40% of the actual warming.
    Gore acknowledged to Newsweek that the findings could complicate efforts to build a political consensus around the need to limit carbon emissions.
    “Over the years I have been among those who focused most of all on CO2, and I think that’s still justified,” he told the magazine. “But a comprehensive plan to solve the climate crisis has to widen the focus to encompass strategies for all” of the greenhouse culprits identified in the Nasa study.
    The former vice-president has been working behind the scenes to try to nudge the White House and Congress to move forward on a 920-page proposed law to cut America’s greenhouse gas emissions and encourage its use of clean energy sources like solar and wind power.”
    “Al Gore’s Inconvenient Truth sequel stresses spiritual argument on climate
    Nobel winner adapts fact-based message to reach those who believe they have a moral duty to protect the planet in Our Choice: A Plan to Solve the Climate Crisis”
    http://cnews.canoe.ca/CNEWS/Environment/2009/11/03/11617491-reuters.html

  56. Therefore this kind of study clearly shows that the planet’s climatic evolution cannot be inferred from temperatures and that the notion of global warming or cooling derived from surface temperature is a myth.

  57. With the greatest respect to Dr. Pielke, I don’t understand this study at all. Take a look at Figure 9. It shows that:
    • when forest is converted to barren, the temperature rises … and when barren is converted to forest, the temperature rises.
    • when grass/shrub is converted to barren, the temperature rises … and when barren is converted to grass/shrub, the temperature rises.
    • when urban is converted to barren, the temperature drops … and when barren is converted to urban, the temperature drops.
    What am I missing here?
    The main problem is the huge range of the 95% confidence intervals. Of the fifteen possible pairings, I see only one pair (agriculture to grass/shrub, grass/shrub to agriculture) where the confidence intervals don’t overlap.
    In all the rest (as is confirmed by the paradoxical results I quote above), the intervals overlap. It seems to me that the only scientifically sustainable conclusion is that when you go from agriculture to grass/shrub, it warms up, and vice versa.
    Clearly, I don’t understand what is going on in the study. Help, anyone?

  58. Politicians won’t want to know about it. Reducing land clearing and deforestation is too political. It is far easier to blame CO2 and win votes by adding new taxes.

  59. Re: Willis Eschenbach (12:40:34)
    Willis, you aren’t missing anything (good eye). You have recognized the major inconsistencies with this paper.
    What caught my eye in figure 9 were the claims concerning urban areas converted to forest, grass/shrub, agriculture etc. It conjured up in my minds-eye visions of cities being bulldozed to create farmland.
    I think the problem is that the land use land cover change was estimated using satellite-based AVHRR data, which is iffy at best. For example, when a new suburban development is built, the trees are freshly-planted and small. As it ages, the trees grow taller, their crowns spread and eventually begin to join. The AVHRR classification then changes from “urban” to “forested”. How “urban” becomes “agricultural” I can’t imagine.
    I also agree with your observations of the CI’s in fig 9. There really isn’t much useful information in that figure.
    I was also bothered by the authors statements of the reliability of the results in that figure due to sample size, sometimes lesser, sometimes greater, with no mention of what the sample sizes were.
    Frankly, I think the Pielke Sr. group has been banging the “land use change” drum a little too loudly, and got a little too carried away with this paper.

  60. Once again I find myself bringing to attention here the Palouse formations http://en.wikipedia.org/wiki/Palouse. The hills of fertile soil are basically silt dust blown in from other regions during times of drought, similar to the dust bowl era but clearly not related to human activity. The dust bowl era has no relation to human activity in that the weather pattern variation that set up the blowing dust had nothing to do with human activity. Some say that farming practices made it worse. I beg to differ. All you have to do is measure the depth of the Palouse soil to know that nature trumps humans. Everytime.

  61. Well it has been confirmed. There is a bias in the surface records of temperature. The bias is towards a greater warming trend than actual, as recorded by satellite records.
    New Paper Documents A Warm Bias In The Calculation Of A Multi-Decadal Global Average Surface Temperature Trend – Klotzbach Et Al (2009)
    “An Alternative Explanation For Differential Temperature Trends At The Surface And In The Lower Troposphere” By Klotzbach Et Al 2009

  62. 240 years ago, the great historian, Edward Gibbon appealed to changing land use as the cause of a warming climate.
    Part I of Chapter IX: The State of Germany till the
    Invasion of the Barbarians, in the Time of the Emperor Decius
    of The
    History of the Decline and Fall of the Roman Empire
    by Edward
    Gibbon originally published in 1776
    :
    Some ingenious writers have suspected that Europe was much colder formerly than it is at present; and the most ancient descriptions of the climate of Germany tend exceedingly to confirm their theory. The general complaints of intense frost and eternal winter, are perhaps little to be regarded, since we have no method of reducing to the accurate standard of the thermometer, the feelings, or the expressions, of an orator born in the happier regions of Greece or Asia.
    But I shall select two remarkable circumstances of a less equivocal nature. 1. The
    great rivers which covered the Roman provinces, the Rhine and the Danube, were frequently frozen over, and capable of supporting the most enormous weights. The barbarians, who often chose that severe season for their inroads, transported, without apprehension or danger, their numerous armies, their cavalry, and their heavy wagons, over a vast and solid bridge of ice. Modern ages have not presented an instance of a like phenomenon. 2. The reindeer, that useful animal, from whom the savage of the North derives the best comforts of his dreary life, is of a constitution that supports, and even requires, the most intense cold. He is found on the rock of Spitzberg, within ten degrees of the Pole; he seems to delight in the snows of Lapland and Siberia: but at present he cannot subsist, much less multiply, in any country to the south of the Baltic. In the time of Caesar the reindeer, as well as the elk and the wild bull, was a native of the Hercynian forest, which then
    overshadowed a great part of Germany and Poland.
    The modern improvements sufficiently explain the causes of the diminution of the cold. These immense woods have been gradually cleared, which intercepted from the earth the rays of the sun. The morasses have been drained, and, in proportion as the soil has been cultivated, the air has become more temperate. Canada, at this day, is an exact picture of ancient Germany. Although situated in the same parallel with the finest provinces of France and England, that country experiences the most
    rigorous cold. The reindeer are very numerous, the ground is covered with deep and lasting snow, and the great river of St. Lawrence is regularly frozen, in a season when the waters of the Seine and the Thames are usually free from ice.

  63. http://www.nytimes.com/2007/08/14/science/earth/14fenc.html
    At Australia’s Bunny Fence, Variable Cloudiness Prompts Climate Study
    By SONAL NOTICEWALA
    August 14, 2007
    A fence built to prevent rabbits from entering the Australian outback has unintentionally allowed scientists to study the effects of land use on regional climates.
    The rabbit-proof fence — or bunny fence — in Western Australia was completed in 1907 and stretches about 2,000 miles. It acts as a boundary separating native vegetation from farmland. Within the fence area, scientists have observed a strange phenomenon: above the native vegetation, the sky is rich in rain-producing clouds. But the sky on the farmland side is clear.
    Researchers led by Tom Lyons of Murdoch University in Australia and Udaysankar S. Nair of the University of Alabama in Huntsville have come up with three possible explanations for this difference in cloudiness.

  64. To Willis Eschenbach
    Hi Willis
    I agree with you, all the more as all the ‘inconsistencies’ you mention are listed in our conclusion. Excerpt:
    “In addition, our analysis shows that there is not always a straightforward relationship between the different types of conversions: for example, (1) both conversion of urban to barren and the opposite resulted in slightly negative OMRs; (2) there was a weak warming of areas that shifted from bare soils to grassland/shrubland and for the opposite as well and (3) both conversion from forest to grassland/shrubland and the opposite were associated with a weak warming. In a number of cases, our estimates were hampered by the lack of significance due to a small number of samples. All these considerations lead us to conclude that the effects of LULC changes on temperatures trends are significant but more localized studies need to be conducted using high-resolution datasets”.
    These results are what we obtained from the analysis that examined the trends in areas that changed from one type to another using the NLCD 1992–2001 Retrofit Land Cover Change. Of course, the OMR values used in this specific analysis span the same period (as explained in section 2 of the paper).
    While there is still much work to do, our results demonstrate a clearly discernible effect due to landscape change.
    Some contributions in this blog pointed out the shortness of the study period to assess changes due to land use. Agree, but for now, despite the shortness of the period of acquisition, the NLCD dataset (30 meters grid spacing) is the only one that breaks down the data into non-changed vs. changed areas (a total of 87 classes). A closer look at this dataset shows that during this short period, some conversion have been important: e.g. (i) urbanization, especially from agriculture and forest to urban; and (ii) conversion to croplands, especially from barren and grass/shrub.
    As mentioned in some contributions, there are some odd conversions, such as urban to barren or urban to grass/shrub, but our study did not invent these conversions. That’s the NLCD datasets that identifies such land use/cover conversions.
    That said, it is important to have in mind that OMR values reflect not only land use/cover changes, but also a number of other factors such as various climatic and non-climatic biases that affect near-surface temperature trends, including the quality of station siting which, so far, has not been included in temperature trend assessments. Moreover, factors such as near-surface moisture and wind speed can influence temperature trends and make them unrepresentative of the regional trends. As a result, OMR should not simply be read as “warming” or “cooling”.
    Last but not least, the issue that is presented in the press release focused only on temperature trends with respect to LULC types. The press release only reports on part of our research [in this paper and a number of other peer reviewed papers] on the issue of the uncertainties associated with homogeneity adjustments and multi-decadal surface temperature trends.
    Regards

  65. Dr. Souleymane, many thanks for your comments.
    I believe that the answer to the inherent contradictions I pointed out lies in the nature of your study.
    In your study, you used the difference between the USHCN data, and “reanalysis” data. I have great problems with “reanalysis” data. For example, see my analysis of the NCEP reanalysis data here. It shows that the NCEP reanalysis data does a very poor job at replicating the amplification behaviour of the atmosphere.
    If you are going to use reanalysis data to do the type of analysis you have done, it seems to be incumbent on you to first verify the reanalysis data. You do not appear to have done so. In your study you say

    Trends of monthly mean temperature anomalies show a strong agreement, especially between adjusted USHCN and NARR (r = 0.9 on average) and demonstrate that NARR captures the climate variability at different time scales.

    However, this is a necessary but not sufficient investigation. The NARR is based on observations, so we would expect it to be close. But that is not enough.
    What you need to look at is, when the USHCN disagrees with the NARR, what is the reason for the disagreement? These disagreements could be from a variety of causes, including LU/LC changes, random error, bad computer programming or assumptions, or other environmental factors.
    You have assumed that the difference is due to changes in LU/LC. However, this is something that needs to be proven rather than asserted.
    And in fact, your study establishes that there is a very good chance that the differences are merely random. I say this because of the contradictions in the results that I highlighted above. Since they go both ways, it certainly leaves random fluctuations high on the list of possible reasons.
    There are other possibilities as well. For example, in the map shown at the top of this thread (Figure 5 in your study), there are huge areas where the NARR is significantly different from the USHCN data. One of them is roughly contiguous with the Rocky Mountains … so the first thing I would check is to see whether there is a correlation of the OMR (observation minus reanalysis) data with elevation data. You say there is a “qualitative correlation” that explains this (shown in Fig. 6 of your study), but absent a quantitative correlation, I am not convinced. I get nervous when someone reports a qualitative correlation and does not proceed to do and report a quantitative correlation.
    Because frankly, I have a very hard time believing that there have been large LU/LC changes over the entirety of the Rocky Mountains as shown in the map at the top of this thread. For another example, look at the area shown in blue that stretches from Southern California to Nevada … I’ve driven that stretch many times, and there is no common LU/LC change that covers that area. Over much of it, there is little development of any kind. So clearly, while LU/LC may be a factor, there are also some other thing at play that affect large areas.
    In short, while an OMR analysis may be able to be related to LU/LC at some future date, there are obviously huge confounding factors which have not been considered, much less allowed for in your analysis. You cannot simply say that OMR and LU/LC are correlated without removing those factors.
    And this is clearly demonstrated by your results. If the OMR method were valid and the confounding factors had been removed, we would not see the curiosities I note above, viz:
    • when forest is converted to barren, the OMR rises … and when barren is converted to forest, the OMR rises.
    • when grass/shrub is converted to barren, the OMR rises … and when barren is converted to grass/shrub, the OMR rises.
    • when urban is converted to barren, the OMR drops … and when barren is converted to urban, the OMR drops.
    These contradictions demonstrate that using the OMR method to analyse LU/LC is not ready for prime time. It may be in the future, but at present, it gives contradictory results.
    Again, Dr. Fall, many thanks for your comments. I am impressed that you are willing to publicly defend your results, as this is extremely uncommon with climate scientists.

  66. Well, I was just speculating about elevation being a factor in my post just above, but today I chanced onto this …

    Does Global Warming Decline with Increasing Elevation?
    Reference

    Seidel, T.M., Weihrauch, D.M., Kimball, K.D., Pszenny, A.A.P., Soboleski, R., Crete, E. and Murray, G. 2009. Evidence of climate change declines with elevation based on temperature and snow records from 1930s to 2006 on Mount Washington, New Hampshire, U.S.A. Arctic, Antarctic, and Alpine Research 41: 362-372.
    Background
    The authors write that “future predictions of climatic change and impacts on mountain ecosystems are frequently based on the most proximate low elevation data or on extrapolations from other mountain regions.” However, they say that “using surrogate climatic data to describe potential responses by mountain biota can result in compromised conclusions.” As one example, they note what they call “the assumption that alpine ecosystems may be at great risk,” as most climate alarmists vociferously contend they are, because of what they typically describe as unprecedented global warming.
    What was done
    Working at Mount Washington (44°16’N, 71°18’W, the highest point in the northeastern United States), Seidel et al. compared seasonal and annual temperature trends, growing and thawing degree-day trends, and trends in two indices of snow season length for the summit (1914 m a.s.l.) and for Pinkham Notch (a mid-elevation site on the mountain’s eastern side).
    What was learned
    Based on data for the period 1935-2003, the seven scientists determined that at the mid-elevation site “there is a statistically significant warming in both annual and summer temperatures, with greater warming than that observed on the summit and less than that reported for lower elevations in the region.” In addition, they say summit temperatures, “though trending towards warming, do not exhibit a statistically significant change.” What is more, they say there is evidence that “resistance to climate warming at the higher elevations on Mount Washington has considerable tenure,” citing the work of Spear (1989), who, “using pollen and plant macrofossil records from Mount Washington and surroundings, concluded that since 5000 years BP, the subalpine forest and treeline-alpine ecotone boundary on Mount Washington has not exhibited demonstrable shifts.”
    One explanation for this mountaintop “climate stasis” may be related to the fact that Grant et al. (2005), as Seidel et al. describe it, estimated that “the summit of Mount Washington experiences free-atmosphere (troposphere) conditions on 50% of days in both summer and winter,” so that “the summit exhibits a weak but not statistically significant warming trend, because during these conditions the summit would not necessarily be coupled with events observed from the surrounding regional lower elevation trends.”

    SOURCE

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