liveonearth (liveonearth) wrote,
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Urban Global Warming


Painting: "Sleepy Hot City" by Fiona Nasr
Notes here from interesting article:

Notes from:
Urban heat; Cities sizzle as more people move in, by Sid Perkins.
A feature article in Science News, dated April 11th, 2009, Vol.175 #8 (p. 26)

SOURCE:
http://www.sciencenews.org/view/feature/id/42196/title/Urban_heat

PROBLEM #1: THINGS REALLY ARE HEATING UP
--Intergovernmental Panel on Climate Change says Earth’s average global temperature has risen about 0.74 degrees Celsius in the past century (SN: 2/10/07, p. 83)
--most likely due to increasing CO2 (and other heat trapping gasses) in atmosphere
--IPCC scientists suggest this warming trend will accelerate
--they estimate the average global temp increase another 0.4C in the next 2 decades

PROBLEM #2: PEOPLE AREN'T GOING TO STOP HAVING BABIES
--population growth
--current pop: 6.6 billion people
--25% increase (another 1.65 billion) predicted by 2030 (SN: 10/13/07, p. 235)
--even with improved energy efficiency, more pop-->consumption-->gasses-->warming

PROBLEM #3: MORE AND MORE PEOPLE LIVE IN CITIES
--urbanization
--population growth is higher in cities
--due to efficiency of agriculture (not everyone has to grow food)
--much of population growth is in coastal cities
--sea levels are rising
--as cities heat up-->use more AC-->emit more waste gasses-->heat more
--urban air pollution has direct effect on people too
--urban dwellers at increased environmental risk, says Walt Dabberdt
-- Kai N. Lee = a political scientist at David & Lucile Packard Foundation says:
--in 1740, 2/3 of workers in England and Wales — were farm workers (now less than 1/4)
--today, in developed nations <5% of pop engages in agriculture
--in 1800, about 2 percent of the world’s pop was urban
--in 2007 more than half of worlds pop in cities
--world’s rural population currently peaking and expected to decline
--United Nations demographers estimate that >60% of world’s population in cities by 2030
--2030 was the date by which another scientist (in recent post) predicted global food crisis
--most growth in developing nations: China, India, Sub-Saharn Africa
--Sub-Saharan Africa already has more urban dwellers than the combined pops of US and Canada
--bulk of urban growth expected in cities now smaller than 500,000 people!!!
--urban growth — will be about 1.3 million people/week worldwide by 2030

URBAN HEAT ISLANDS
--temperatures are higher in cities than in the country: “urban heat island” effect
--low "albedo" = absorbs more of sun's radiation than natural landscape
--difference is several degrees
--Walt Dabberdt was president of the American Meteorological Society in 2008 and chief science officer for Vaisala Corp., an international manufacturer of weather-monitoring systems and instruments, lives in Boulder, CO
--“Cities are major contributors to anthropogenic climate change,” says Dabberdt
--Dabberdt says urban areas responsible for approx 80% of greenhouse gas emissions
--this includes vehicles, industry, and coal-fired power plants located elsewhere but serving the energy needs of the cities
--annual meeting of the American Meteorological Society in Jan 2009 was held in PHX
--studies on reducing emissions and heat island effect

CITIES WARM BECAUSE RAINWATER RUNS OFF
--David J. Sailor, mechanical engineer
--Portland State University in Oregon
--urban proliferation of impervious surfaces
--increase in rain-shedding surfaces such as roofs, pavement, sidewalks and streets
--drainage goes to gutters-->rivers
--loss of evaporative cooling
--tall buildings close to each other reduce ability of all to cool at night

WHERE URBAN HEAT COMES FROM, BESIDES THE SUN: CARS, BUILDINGS, INDUSTRY
--human activity generates immense quantities of heat
--burn 1 kg gasoline-->45 million joules of energy, enough to melt and boil 60 kg ice
--car @ 10km/LITER (24mpg) goes 1 km-->enough heat to melt (boil?) 4.5 kilograms (10 lbs) ice
--waste heat from lighting, heating and making hot water is waste heat in environment
--urban anthropogenic heat: approx 1/3 from tranport, 1/3 from buildings, 1/3 from industry
--all cities are different
--Houston, TX is heated by nearby oil refineries

STUDY OF PHOENIX BUILDINGS
--Brent Hedquist, urban climatologist at Arizona State University in Tempe
--April 2008
--used portable weather stations and thermal imaging cameras to carry out a round-the-clock study in downtown Phoenix
--some studies have shown that the core of PHX is 7-11 degrees CELSIUS warmer than surrounding
--PHX is one of the fastest growing urban areas in the nation
--facades of dense concrete/brick can reach temperatures of 45°C/113°F during day and retain heat into night
--glass and metal buildings cool quickly after the sun went down
--daytime absorption and nighttime heat loss also depends on angle, building distances, and wind speed & direction

SOLUTIONS: MODIFY YOUR ROOF
--"green roof" allows for plant life, less heat aborption, less runoff, evaporative cooling, CO2 consumption, O2 production
--Sailor suggests that converting all roofs in 2 square km area of Portland would reduce daytime temps up to 0.5 degrees C (SN: 9/4/04, p. 152)-->less AC-->less emissions
--Joby Carlson, research scientist at ASU in Tempe
--in desert try painting your roof white, or cover it with white gravel
--experiment in AZ showed roof color & albedo makes big difference, indoors and out
--also changed peak demand for electricity

ANOTHER PROBLEM THAT COULD BE A SOLUTION: HEAT IS WASTED
--coal and natural gas used for electricity generation: 2/3 of energy-->waste heat
--waste heat could be put to use except for remote location of generation facilities
--Thomas R. Casten, chairman of Recycled Energy Development in Westmont, Ill
--Phil Schewe of American Institute of Physics in College Park, Md
--January-February American Scientist
--example of good use of waste heat: Consolidated Edison in New York City delivers heat to thousands of buildings in Manhattan via the world’s largest commercial steam system
--waste heat from industries could be used to generate more electricity
Tags: automobiles, climate change, coal, electricity, energy, population, science, the long emergency, urban
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