Urban Global Warming

[liveonearth]

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

Comments

[(Anonymous)]

Nice shout out to Tom Casten about waste heat and energy recycling. I'm associated with his company, Recycled Energy Development, and this efficiency method has absolutely staggering potential. EPA and DOE estimates suggest that energy recycling could cut U.S. greenhouse gas emissions by 20%. That's as much as if we pulled every passenger vehicle from the road. The main obstacle is the set of regulations that protect electric utilities and stifle competition. We should be doing a lot more on this front.