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Getting into the science of climate change  RSS feed

 
Rob Meyer
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Hey all,

I was wondering if anyone could help me out with a thought I just had. I am wondering how exactly the planetary increase in temperature has been related at all to the increase in the number of heat absorbing surfaces across the planet, i.e. the increase in the number of cities and the heat island effect that comes along with them. If this is indeed a significant factor, how much of a significant factor is it, and have the calculations been done on how exactly the greening of cities may benefit the overall global temperature? I wonder if it would be a large enough impact to almost make CO2 reduction unnecessary, or at least somewhat arbitrary. I guess what I'm wondering is if urban greening could possibly be the lynch pin for remediation of the global temperature to our preferable range. Have we officially reached climate control status as a species?

Just some thoughts I've been having, hopefully you'll share yours.
 
Jonathan Byron
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Certainly the urban heat island effect can have a dramatic effect on the microclimate and even have regional effects - five to ten degrees for a city, even more on a local basis. Is this adding a significant amount to the global energy budget? I don't know. But trees are a rational response to balance the concrete, blacktop, and roofs of the urban environment.
 
                                      
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Hi,

i am very interested in this as well.

and i think it goes even further than just the urban heat islands.

Think about it, vegetated surfaces will create chemical energy from sunlight through photosynthesis. unvegetated surface (concrete, pavement or bare soil alike) will turn the sun's energy in to warmth/heat*. We all know how significant this can influence microclimate by experience, several degrees in temperature from a well vegetated area to a bare soil or concrete area.

When on hot days we look for refuge between trees we generally asume it is the shade that provides this cooler microclimates, when it is actually mostly because of the suns energy being turned into chemical energy in stead of heat. The shade merely reduces the direct sunlight to our skin (heating our own temperature), the photosynthesis actually reduces the temperature of our surroundings.

especially trees are very effective in making chemical energy out of sunlight.

If we take these significant differences into consideration. And we take the amount of deforestation that has been going on for the past century or so. (plus al desertification and urbanisation). It would seem this would have a large effect on global warming.

My question for quite some time now is:
Has this ever been studied?

hoping anyone here has more info,
but i will also ask aroud in the climate change and peakoil scene...

*= light-> short wavelenght energy into heat-> long wavelength energy.
 
Jonathan Byron
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All of the global climate models incorporate albedo (reflectivity) of the planet.

James Lovelock wrote about 'Daisy World' in 1983 - a hypothetical self-regulating planet covered with growing flowers. He noted that if temperatures were to cool for whatever reason, darker flowers would have an advantage, their would be random mutations towards darker flowers, they would multiply faster, absorb more light, and the planet would ultimately become warmer. And if the planet became hotter, lighter or white flowers would be less prone to overheating, they would be selected for and breed faster than overheated dark flowers, and eventually the planet would reflect more light and be cooler.

Lovelock is all for re-forestation as best I understand, but he doesn't see that as more than a drop in the bucket compared to the massive geochemical changes we are subjecting the planet to. We are at the point where the Arctic region is ice free for much longer portion of the summer, and this means less light is being reflected back into space and more is being absorbed there... a thinner layer of ice reforms in winter, but the Arctic winters only get a few hours of indirect light - summer ice is the critical factor.

Wikipedia Page on Daisy World

Think about it, vegetated surfaces will create chemical energy from sunlight through photosynthesis. unvegetated surface (concrete, pavement or bare soil alike) will turn the sun's energy in to warmth/heat*. We all know how significant this can influence microclimate by experience, several degrees in temperature from a well vegetated area to a bare soil or concrete area.


Yes, plants tie some of the energy into a chemical form via photosynthesis (3 to 7%), and this energy is potential and not reactive until the plant material is burned or metabolized by other life forms. But most of the cooling comes from shade and evapotranspiration of water. With evaporation, the air temperature is reduced but the heat is still 'latent' in the atmosphere. On a local scale, that may not be an issue, but on a regional or global scale, it is very important. The 'effective temperature' is what is important to most life forms, 90 degrees F in the dry desert is very different from 90 degrees F in a moist tropical area (they have very different 'effective temperatures'). If the air is dry we can cool ourselves by sweating or misting and we benefit from the evaporation. If we raise the humidity for a larger area, we don't benefit the same way.

Vegetation is a partial solution, not a panacea. But many partial solutions are all that we have, they will have to do.
 
John Sizemore
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Location: West Virginia/ Dominican Republic
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One of the arguments during the climate gate situation was the fact that many of the monitoring stations that were used to show an average increase had been in rural areas of the past and now was in cities due to urbanization.
While the argument is accurate to the point of not actually showing an average increase but a local increase the statistics still show an increased temperature in a portion of the surface.
Reforestation of not only the rural areas is needed but a transition to earth sheltered homes with living roofs in temperate areas and possibly narrow houses nestled among trees in the tropics. The grey water output of most houses alone could create lush oasis in even desert climates.
There was a study years ago that showed green plants build a micro bubble of air around their leaves that tries to maintain 73 degrees. NASA was involved, I don’t have the reference off hand but I remember it was discussed because the plants would actually raise the temperature around them if it was less the 73 degrees.
Even areas such as old landfill sites would be great for raising cattails for biofuel. 17000 gallons of ethanol per year and would be a great means of sewage treatment. The evaporative cooling from an artificial wetland would be superior to just a grass covered wasteland that is no longer useful for anything.
 
Jonathan Byron
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Another component of the urban heat island is the huge amount of energy being poured into cities. We heat our leaky houses, run cars and billions of appliances - mostly with solar energy that was stored up in fossil fuels gradually over millions of years, but it is being released in small areas over a few centuries.
 
              
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OP, actually, on the net basis of the planet, i suspect the contrary. Concrete, metals, and glass tend to have a higher reflectivity than plants or dirt. furthermore, if you hold your hand above a concrete slab on a sunny day, the heat you feel is heat radiated away from the planet. i think the difference can't be more than a percent or two.

i did a quick check and google says 3% of earth is urban areas. looking around, i'd say at most 10% of that is buildings and roads so we are talking about 0.3% of 2% (0.006%) maybe.
 
branimir marold
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toan tr wrote:OP, actually, on the net basis of the planet, i suspect the contrary. Concrete, metals, and glass tend to have a higher reflectivity than plants or dirt. furthermore, if you hold your hand above a concrete slab on a sunny day, the heat you feel is heat radiated away from the planet. i think the difference can't be more than a percent or two.

i did a quick check and google says 3% of earth is urban areas. looking around, i'd say at most 10% of that is buildings and roads so we are talking about 0.3% of 2% (0.006%) maybe.


shhhh it's reflected out of this planet anyway

sorry for asking, but our you serious?
 
              
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yeah. quite.
 
branimir marold
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where is heat "reflected"?

from where it comes in the first place? (heat)

I thought space is cold

now I'm quite serious about this question cause I'm not sure I get some facts right, if you can answer would appreciated!
 
              
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the heat is not really heat, it's radiation, so it's more energy than heat. and it goes into space.

heat comes from the sun, mostly in the form or radiation (in this case sunlight).

and space is cold, but it's also really big and mostly devoid of matter to capture any of the radiation and turn it to heat, so it stays cold.
 
branimir marold
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toan tr wrote:the heat is not really heat, it's radiation, so it's more energy than heat. and it goes into space.

heat comes from the sun, mostly in the form or radiation (in this case sunlight)............


I respect a will to explain but I'm not sure in .. I can't find logic :s

I'm not saying you don't know what you talking about, maybe it's just communication issue

thanks for everything

p.s. maybe quick check with google isn't so representative argument

 
Jocelyn Campbell
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Check out this video from NASA, http://www.nasa.gov/topics/earth/features/2011-temps.html.

It's 131 years of global temperatures in 26 seconds.

The carbon dioxide level in the atmosphere was about 285 parts per million in 1880, when the GISS global temperature record begins. By 1960, the average concentration had risen to about 315 parts per million. Today it exceeds 390 parts per million and continues to rise at an accelerating pace.


Did someone say something about trees?
 
Ken Peavey
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Thread moved from Permaculture to Meaningless Drivel.
 
Burra Maluca
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branimir marold wrote:where is heat "reflected"?

from where it comes in the first place? (heat)

I thought space is cold

now I'm quite serious about this question cause I'm not sure I get some facts right, if you can answer would appreciated!


Electromagnetic waves have all different wavelengths, and the difference in wavelengths produce different effects. Some we can detect with our eyes - we call this light, and our brains allocate different sensations to slight variations in the spectrum of wavelength that we detect. That is what colour is.

Other wavelengths have other effects. Some wavelengths travel happily through space but when they hit anything more solid, like earth or atmosphere, some of the energy they contain is absorbed, creating what we call heat. Any electromagnetic waves which bounce off are now of a different wavelength, and thus have different properties to when they first arrived, and are even more likely to be absorbed by molecules in the atmosphere than when they first passed through.
 
Brice Moss
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Location: rainier OR
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I'm studying environmental science at Portland State and it so happens we have a professor and team doing research on the urban heat island effect and how it relates to the total energy budget of the planet right now he estimates a few more years to completion and when I asked if he has an idea how its going to look he answered with one word "complicated"

you see those hot black surfaces lose heat through radiation to space at night just as much as they gain heat by absorbing radiation during the day thus higher highs in the summer and lower lows in the winter are one of the expected and observed results, but its more complicated than that

the impervious nature of roofs roads sidewalks etc. result in water not being absorbed into soil which changes the heat balance and effects the vegetation types that grow close by

its not just the roads and concrete roofs are also usually dark and absorb/transmit radiation easily in the form of heat lawns and parks are significantly different than forests and shrubs,

evapotranspiration (the evaporation of water from plant leaves) is also greatly different in city areas and as evaporation and condensation involve huge heat budgets with little temp change. This muddies the picture, a lot.

I'm going to be doing some data entry for this project http://www.fsl.orst.edu/eco-p/ultra/data-management.html which may be able to say something about one or two of these factors in the Portland/Vancouver area in five years or so, if our pilot surveys show enough promise to get us the funding.

wikipedia has a nice overview of black body radiation, http://en.wikipedia.org/wiki/Black-body_radiation then one has to adjust to the fact that there are no real black bodies, an that the earth is a complicated system with moisture dust and other stuff in the atmosphere absorbing and radiating energy/

space cannot be "cold" only matter has temperature and the defining point of space is that there is very little matter.

I hope that even if I haven't answered any questions I've made it a bit easy to understand why climate research is tricky
 
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