From PBS last night: From Rooftop to Alleyway, Chicago Fights Extreme Urban Heat With Greener Ideas
One of Chicago’s most beautiful and hidden gardens is located on top of City Hall, part of an effort to ‘green’ roofs in order fight rising temperatures. Hari Sreenivasan reports on the actions the city of Chicago is taking to mitigate climate change in an urban landscape.
Here’s the video report:
THOMAS PETERSON, Climatologist, National Oceanic and Atmospheric Administration: We look at temperature at rural stations and we look at temperatures at urban stations.
And we see if they are showing the same thing in the long-term trend variability and change. And they are showing the same thing in our record, both in the U.S. record and in the global record. What we find is when we account for the different factors that impact temperature at a location, we see that the temperature in urban sites is warming at about the same rate as temperature in rural sites.
From transcript at:
http://www.pbs.org/newshour/bb/climate-change/july-dec12/climate_10-09.html
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Dr. Peterson sidestepped the real seasonal heat issues for cities. It isn’t the trend, but the absolute temperatures. Heat waves born in urban heat islands aren’t so much about trends like 0.7C over the last century, but they are about the high temperature that day. Anybody who has ever watched a TV weather report or driven a car from downtown to the suburbs in the evening can see how cities are warmer and retain heat longer.
In a few days, I’ll be releasing a first ever live rural-urban temperature comparison project, never before done, that will help provide a near real-time window on this problem. Its something that should have been done a long time ago, and could easily have been done anywhere in NOAA and especially at NCDC. But NCDC’s Peterson and others don’t like the sorts of comparisons I’m about to make, which is why they don’t like to talk about the absolute temperature differences between urban and rural stations on national TV.
But I suppose his belief isn’t surprising, when you live in an homogenized data world, every temperature looks the same to them.
h/t to R. Cook
First you build a park on your roof, then you extend the roof to get more green area, then roofs from adjacent houses merge … and before you notice, you’re living in a cave.
But honestly, I am a fan of green roofs.
My roof’s been covered in green moss for ages, but I haven’t noticed any serious changes in temperature. Perhaps I should go and paint it white, or black, or something…
Albedo determines the percentage of solar energy absorbed by a surface (as heat). Greening a surface will in almost all cases decrease the albedo and hence increase the solar energy absorbed. That is increase the heat in the urban environment.
Greening decreases temperatures by increasing evapotranspiration (humidity).
Artificial rain would probably be cheaper and more effective.
Places with high and recent urbanization growth such as India and China should be able to provide all the data we’ll ever need about UHI
Interestingly enough, the local weather forecasts on our local BBC TV station, has started noting that temperatures in the countryside, will be a few degrees lower than the one’s on their charts, as we’re getting sub 10C overnight temperatures.
When I lived in the UK and watched local (midlands of England) weather forecasts there was a tacit assumption that it would be 3’C warmer in town that in the rural areas. UHI was never mentioned though.
All those air conditioned buildings pumping heat to the outside will also increase the UHI effect.
So what is this awful warming blamed on – the sunshine? – or 0.01% of the atmosphere?
Returning to the old way of “Turfing” our roofs may making it warmer indoors which may increase the demand for more Air Conditioning and increased fossil fuel use.
PS. Now that the “Hose-pipe ban” has been lifted in the UK the farmers find their potato – crops have rotted in the waterlogged soil. –
Water logged soil weighs a lot more than most “normal” roof coverings do so watch out for the possibility of collapsed roofs due to AGW in the future.
Seems like it would be difficult to get a good urban/rural comparison from official American records.. Nearly all of them are at airports, typically 10 miles away from dense cities. Airports have their own heat sources, but they’re not representative of mid-city temps.
Kindly rename UHI as “HI” as it significantly exists even in small towns and a comparison of small versus large cities is often used to discredit UHI as a cause of upward temperature trends.
Even small towns of 5000 people have undergone massive changes that have increased the temperature: trees are gone, single family homes are now high-traffic offices and multifamily, lawns have been replaced by black parking lots, traffic has increased. air conditiioning which was non-existant 50 years ago is now the norm, etc, etc, ….and towns are often located in valleys which trap this heat. Not uncommon to see them 5-10 degrees warmer than surrounding rural areas.
Maybe call it LTBCHI – “Little Town Big City Heat Island”
Even in the countryside there is a big difference in the amount of heat absorbed/radiated from different land surfaces. As a farm student I had to bicycle home several miles in the evening, and there was a very noticeable difference when passing by stubble fields ( light fawn colour ) which were quite cool, compared with fields that had been ploughed (dark brown ) which gave off a noticeable amount of heat. The ploughed fields had obviously absorbed a lot of radiation during the day, but would they lose all that extra during the night?
Which temperature would be the one to record as the correct rural temperature, stubble or plough?
Would the average temperature of the different land surfaces over 24 hours be the same?
If there was one hour of very hot sunshine in the afternoon, but the rest of the day was cool, would the average taken by adding the max and min temperatures for the day and dividing by two be skewed?
Green rooves are at the heart of a local business kerfuffle. Sod roofs are a local cultural tradition and so are the goats used to mow the grasses. A business has effectively servicemarked the use of goats and, with the connivance of the courts, demands royalties on goats mowing roofs.
Kasuha says:
October 10, 2012 at 1:35 am
I’ve always been tempted to live in a cave. Save lots on cooling costs, humidity control might be an issue. With the large panel televisions you could have closed circuit TV from the top of the hill and have a view too!
An underground house is an okay compromise too.
“Greening” the roof top at city hall at great expense and maintenance cost sounds like a good idea to combat the heat citywide since the Amazon jungle is so chilly.
Dear Anthony
I was going to compliment you and your work and bring in Professor Manley who had adjusted the CET because of urban devevlopment.
I went to Wikipedia to get a reference.
Manley, G., 1953. “The mean temperature of central England, 1698-1952.” Quarterly Journal of the Royal Meteorological Society, 79, (340), 242-261.
Manley, G., 1974. “Central England temperatures: monthly means 1659 to 1973.” Quarterly Journal of the Royal Meteorological Society, 100, (425), 389-405.
Both links are to the RMS site and state page not found?
Conspiracy or Cock up or The Team?
Sometimes I have to drive to and through Raleigh from where I live. Raleigh isn’t as big as other major metro areas, but it does exhibit the UHI effect nicely, especially on cool days. Last year I had to drive through Raleigh. When I left home I carefully watched the temperature on my car. The temperature was 4F higher in Raleigh than when I left that morning. Considering it takes me 45 minutes to get to central Raleigh, this wasn’t just the normal heating of the day. After I passed Durham on I-40, the temperature began to fall again. Returning home that evening, I noticed the same effect. If the UHI effect is live and well in a big suburb like Raleigh/Durham, how much more so in places with bigger downtowns.
I like the Idea of Green roof as long as the engineering can prevent dry rot and collapse.
My mother’s family pioneer NW Kansas home is still standing- it is a sod house,,,,
“every temperature looks the same to them.”. Yes. They are all shaded monetary green.
Sounds like an expensive annual replanting scheme will be required in Chicago with its freezing temperatures in the winter (enough to kill off the green roofs) and boiling heat in the summer? Or am I wrong, coming as I do from the UK with a much more moderate climate?
A couple items: 1. Chicago is a very odd city. 2. PBS is about to lose their Govt. subsidy. 3. Chicago also wants to put a violence tax on ammunition.
Now let me get this straight. The brokest city in the brokest county in the second brokest state in the brokest country in the history of the planet has a “Green Projects Administrator”?
Where do I get my money back?
polistra says:
October 10, 2012 at 4:35 am
Seems like it would be difficult to get a good urban/rural comparison from official American records.. Nearly all of them are at airports, typically 10 miles away from dense cities. Airports have their own heat sources, but they’re not representative of mid-city temps.
______________________
Assertions backed up by data?
****
In a few days, I’ll be releasing a first ever live rural-urban temperature comparison project, never before done, that will help provide a near real-time window on this problem. Its something that should have been done a long time ago, and could easily have been done anywhere in NOAA and especially at NCDC. But NCDC’s Peterson and others don’t like the sorts of comparisons I’m about to make, which is why they don’t like to talk about the absolute temperature differences between urban and rural stations on national TV.
****
Cool, Anthony! Maybe this can start a new trend (get it?)
Seriously, this’ll be interesting.
Grumpy says:
October 10, 2012 at 7:01 am
Sounds like an expensive annual replanting scheme will be required in Chicago with its freezing temperatures in the winter (enough to kill off the green roofs) and boiling heat in the summer? Or am I wrong, coming as I do from the UK with a much more moderate climate?
______________________
Why worry about the cost?
The government pays for it, after all.
Shucks, I forgot my sarc tag.
Curiousgeorge says:
October 10, 2012 at 7:19 am
“A couple items: 1. Chicago is a very odd city. 2. PBS is about to lose their Govt. subsidy. 3. Chicago also wants to put a violence tax on ammunition.”
http://www.foxnews.com/politics/2012/10/10/illinois-county-considers-violence-tax-on-guns-and-ammo/
Move all the criminals that are not already there in Chicago to Chicago. Give them all the guns and ammo, etc., they want. No need for jails, they will take care of themselves as they do. Charge tourists who then could watch from the safety of web-cams and garden roof tops. Should be a real revenue maker. PBS could have exclusive coverage.
@Stacey 5:37AM I looked, yes it appears the wiki links are DOA at the Royal Meteorological Soc.
http://en.wikipedia.org/wiki/Gordon_Manley
Books and Selected Papers
Note: The second and third items are those referred to in the footnote above and are available online. They are large PDF files.
Manley, Gordon. Climate and the British Scene: New Naturalist No. 22 (1st edition), Collins, 1952.
Manley, G., 1953. “The mean temperature of central England, 1698-1952.” Quarterly Journal of the Royal Meteorological Society, 79, (340), 242-261.
Manley, G., 1974. “Central England temperatures: monthly means 1659 to 1973.” Quarterly Journal of the Royal Meteorological Society, 100, (425), 389-405.
I went via the search box for Manley to see if this was simply a website change and maybe just dead links, and was directed to this page:
http://www.rmets.org/publications/classic-papers
Scroll down to “M” and you’ll see the links are dead there too. Curious.
Other papers either side of “M” on that page have active links that work. Even more curios, perhaps suspicious.
Philip Bradley, ditto.
It’s the moisture, not the fact that it is green grass. On a 111°F July day try wetting your roof for just two minutes every hour or so and watch your electric meter that day. The effect will astonish you. My electric use in Oklahoma this extra hot summer was the lowest it has been — ever! Moisture management. (just think 10 cu.in.H2O = 1 kWhr)
With Lake Michigan next to Chicago they should just water more. The critical time to decrease nighttime UHI is to water everything for a few minutes, even the roof and south and west brick walls, just as the sun sets. It will suck that extra heat right out. If not, you can instead run your air conditioner for the next four hours to remove it.
Perhaps if they grew pot on all those rooftops, the resulting product could be used to treat those suffering panic attacks about “climate change” (e.g., Dr. Robert D. Stolorow here) . No need to provide any for climate researchers and politicians; they clearly have an adequate supply already.
This is an affordable mitigation strategy that might actually work: green rooftops lower UHI, sales income makes up for some of the questionable public expenditures on “green investments”, and a portion of the resulting product can be reserved to treat climate anxiety. To update Dr. Timothy Leary: turn on, tune in, chill out.
Sounds like a win, win win to me. I wonder if pot works on Polar Bears stressed out about melting ice. Research grant time? How about Zig-Zag sponsoring the next “Row to the Pole” stunt?
/sarc, for the humor impaired.
What is the long term trend in Chicago? How much has it warmed?
I watched this on PBS last night (can’t stop myself watching the election coverage after our local news ends – fascinating watching the PBS pundits trying to spin Obama’s debate performance last week). I was grinding my teeth at the insistence in trying to garble the message about UHI effects with warnings about global warming. Anyone familiar with the issues would recognize the complete incoherence of this aspect of the presentation. The presentation noted an 11 degree difference in some cities due to UHI in comparison with the surrounding country-side, yet tried to scare viewers with a purported 2 degree F temperature increase since 1900, which has supposedly exacerbated the problem.
One thing I have wondered about is how the shadows cast by tall building for much of the day affects the overall temperature? I suppose the increased surface area presented by building sides that are facing the sun more than compensates for the lost gound-level insolation.
@ Grumpy: Green roofs would be planted with indigenous species, which naturally overwinter in our harsh northern climate. The presenters tied global warming with increased rainfall, which presumably would reduce the watering bill.
Curiousgeorge says:
October 10, 2012 at 7:19 am
“A couple items: 1. Chicago is a very odd city. 2. PBS is about to lose their Govt. subsidy. 3. Chicago also wants to put a violence tax on ammunition.”
Better than NYC though, when building new stores in Chicago under the old Mayor Daley, one could hire a consultant to obtain permits from all the various jurisdictions, to which the consultant then paid bribes. I was in the clear since I legally hired a consultant to assist with the obtaining of permits. Did not need to know what he did with the money. In NYC they all wanted cash bribes, which were illegal, so we did not build stores there. Don’t know how either city operates today but assume it’s continued dirty business.
Of course PBS muddles the climate story and moves on to the fascist issue of forcing building owners to carry out a wacky utopian fantasy. I don’t believe that a garden would grow well on thin rooftop soil without intensive management or that anyone would sit up there in a hot Chicago summer. Never mind the cost of removing replacing all the landscaping from a downtown building when it comes time to repair the roof membrane. What building owner would want to pay for and maintain such a roof.
The net result is to deter new business and apartment building leaving the city for more government.
Anthony wrote;
“I went via the search box for Manley to see if this was simply a website change and maybe just dead links, and was directed to this page:
http://www.rmets.org/publications/classic-papers
Scroll down to “M” and you’ll see the links are dead there too. Curious.”
the link to the 1974 paper worked for me. downloaded and saved
Kit
“…we see that the temperature in urban sites is warming at about the same rate as temperature in rural sites.”
This is the state of science these days. Let’s see. Chicago was founded in 1832 at which time the then rural temperature of the present Chicago was about the same as the surrounding rural temperature – 1C lower in 1832. Now Chicago is 3 to 5C warmer than the surrounding rural temp. To me, this works out to a trend of 4-6C growth in a century!! Com’on Thomas P. let’s make sceptism a harder employment than this!
As a landlord that has a number of flat roofs to take care of:
I take a jaundiced eye to green roofs. Flat roofs are hard enough to maintain properly (something I will be doing this weekend). I can’t imagine trying to keep them from leaking when they are covered in greenery.
Now, I do have a small garden on my roof (adding a greenhouse later this month). Everything though is easily moved to allow maintenance. I did have an issue this year due to the extremely hot summer. The plants on my roof ate up a hell of a lot of water (more than my rain barrel could replenish) and suffered damage due to the heat. Roots (the bacteria that fixes the nitrogen) don’t like it hot for long periods of time. My tomatoes and other plants took some damage as the heat wave never seemed to end.
Maybe buildings’ outer walls could be retrofitted with sprinkler-type hoses that would snake down and run horizontally above each floor and that would be turned on during hot days and evenings, to keep them moist. These hoses have tiny holes that each let out tiny streams of water, so they wouldn’t drip much on passersby. it would be worth a test, even if the pilot site looked awkward. This seems like something that could actually work without costing a lot.
We the People hire some guys to do a couple of dirty jobs for all of us, They feel sorry for themselves, it’s so hard and thankless these dirty jobs, so depressing, so they go and build themselves a bloody expensive secret garden on top of the office building we built for them, that wasn’t designed for having tons and tons of dirt and water on top.. Because they need some place to recharge their spiritual batteries after doing these grungy jobs all day. Then they wrap it in some green bs. You fools! You have elected grifters. You deserve what happens to you. Now stay there, and suffer the consequences. Those guys you hired? They aren’t doing the job you hired them for, your city is falling into ruin, and they are stealing you blind! Don’t move away and import your stupidity elsewhere. You broke it, you bought it!
The very worst place you can put an outdoor garden, is on top of a building, in a city in the frost zone. It will destroy your building. Hard winter freezes will crack any containment, and (salty, dirty)water will leak into and corrode your building from above. And remember, because these guys are grifters, they will starve the maintenance needed to keep the building secure from the near-certain disaster of a roof garden.
Now, you fools, go look at an aerial view of Chicago, and find the huge enormous rooftop garden that moderates the Chicago climate. It’s so easy, you should turn off labels,because they are not needed, it’s so easy to spot, a garden that large, you won’t need to zoom in either.
Wayne, your reduced cooling bill will be more than made up for by the unplanned cost of a new roof. All you are doing, by thermal shock cycling of your roofing materials, is hastening its replacement. Leave your roof alone! Enjoy those warm and sunny Oklahoma summers, where the living is easy. The glory of Fall/Autumn is made even more so by having passed through the crucible of summer’s forge.
Anthony – you say – “In a few days, I’ll be releasing a first ever live rural-urban temperature comparison project, never before done…”.
In 1994 I visited the Arizona State U – Office of Climatology – in a building near Sky Harbor. In a corridor behind glass was a landscape model with lights marking locations of temperature sensors – and I am pretty sure the sensors were feeding real time data back to the office.
Can anybody else recall seeing this model ? or being familiar with the project.
Google picks up hints to it in various papers – but I wonder if there is an online description of the network and project aims.
Re Chicago – around 2000 I put up this page on temperature trend comparisons around Chicago and also around Peoria – all degrees C.
http://www.warwickhughes.com/climate/chicag.htm
@ Kit Blanke
yes works for me now too…perhaps they took notice of the concern.
On a 111°F July day try wetting your roof for just two minutes every hour or so and watch your electric meter that day. The effect will astonish you. My electric use in Oklahoma this extra hot summer was the lowest it has been — ever!
Interesting. I had the same idea. Where I live is even hotter than Oklahoma, but less humid.
I have someone coming to repair my irrigation today. I’ll ask him if he has ever installed irrigation on a roof.
October 10, 2012 at 10:05 am | Billy says:
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Billy, Bingo ! Exactly what I was thinking. Some years ago we integrated roof-top gardens and suspended planting into our residential developments … 3 years later, what a disaster as the roots penetrated the membranes and roofs leaked. The mess and cost to repair was horrific.
Philip Bradley, sounds like you must be in Arizona maybe. You might check first to make sure there is no danger of “thermal shock”! Sound akin to CAGW. (just kidding) I didn’t include in my comment that I did do that cooling gradually and for the very same suspicion but my natural skepticism flags just went up. But I will check on that. I mean a roof goes from eighty F to one-hundred forty some F and back every single day in mid summer so what is a few more cycles per year amount to? I just know I sure liked the bit over a hundred bill I’ve managed to lower mine to compared to the bit over three hundred for the previous few summers. (part of that was the installation of a present from my kids, a small window unit, about a hundred bucks, so the main ac now doesn’t have to keep the entire house so cool, just pulls three to five hundred watts and output an amazing amount of cool for a couple of rooms, I sold on the combo!) Maybe that might work for you too if it’s even hotter in your region.
Just saying that any way to keep energy from entering your house in the summer your ac doesn’t have to pump it right back out, and water is a great agent. But sprinklers on the roof? Hmm, how about heavy misters cycled for two minutes every thirty, not even enough to drip off the eves. That did also cross my mind but would have to be totally drainable for the winter though.
rogerknights, now your thinking, but I’ve even refined it a bit over the last two summers. It needs to be water misters with the tiny holes, about nine, so very tiny that the droplets are mostly evaporated by the time they reach the ground. That way it comsumes a very little amount of water. Each summer I’ve had one on my patio, I like the outdoors when comfortable. One running four or five hours in the afternood doesn’t put out enough water to even run off the patio causing puddles, but one day it hit 113F here and my thermometer in the shade read 94F. Much better. It even feels much cooler that that. A little backyard applied fisics. ☺
Wunderground has a ‘feature’ to ‘select a thermometer’ and provides locations of thermometers around the one you started with. I’ve used that to get near instantaneous plots of temperatures around airports (nearly universally warmer in the airport numbers, especially on sunny days / cloudy nights where the sun warmed tarmac keeps the mins high).
I suspect a similar thing could be done with city vs country ‘nearby’.
“Thermal shock” is a real effect. Take a tall cold empty drinking glass, pour in boiling water, guard your eyes.
More specifically, thermal shock is a simple name given to the reaction of a material that is subjected to large thermal gradients: it tears itself apart from the uneven differential expansion/contraction across the gradient. The roof covering heats and cools gradually throughout the day. The temperature gradients throughout the material stay small. But if you are spraying the roof surface with water, you are rapidly cooling just the few millimeters of the surface, while all the underlying material is still at ambient. The surface layer begins to degrade, falls apart, becomes porous.
Yes, rain does the same thing, but rain doesn’t happen every summer afternoon. Your constant wetting of the roof is reducing the roof’s useful life.
Well I am currently putting on a so called green roof. It is called Euroshield. It is made from ground up tires and it looks like wood shake. But Being a global warming skeptic I was attracted to it because it is impervious to hail and has a 100 year warranty and it cut my home owners insurance in half. It goes to show that even idiots can stumble onto a good idea sometimes. Go check out their website. http://www.euroshieldroofing.com/.
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