Earth Gauge » Urban Heat Islands

Cool Your City

espinoza — Thu, 22 Jul 2010 14:30:13 +0000

Urban areas have more buildings, roads, parking lots and sidewalks than rural areas. These hard surfaces trap heat, raising temperatures in cities by as much as five degrees Fahrenheit. Higher temperatures in cities – known as “heat islands” – can increase the amount of energy used for air conditioning, increase air pollution levels and raise the risk for heat-related illnesses. Hot pavement can also heat up rain water runoff as it passes over – when this warmer water reaches our streams and rivers, it can shock fish and other animals that depend on specific water temperatures to survive.

Viewer Tip: An easy way to help minimize summer heat islands is to plant trees and shrubs around your property. Trees help cool urban climates through shading and evapotranspiration (the process of evaporation and water loss through different parts of a plant). The roots of trees and shrubs also absorb rain water runoff, helping to slow the flow of storm water into our rivers and streams.

For more information on using trees and vegetation in urban landscapes, visit http://www.epa.gov/hiri/resources/pdf/TreesandVegCompendium.pdf

Season: Summer

(Source: U.S. Environmental Protection Agency, http://www.epa.gov/hiri/resources/pdf/TreesandVegCompendium.pdf; NASA. “Coastal Cities Turn Up the Heat on Rainfall.” http://www.nasa.gov/centers/goddard/news/topstory/2003/0523urbanrainfall.html)

Cool Tips for Hot Weather

espinoza — Mon, 28 Jun 2010 11:43:48 +0000

Rising temperatures can take a toll on our bodies. Usually, your body cools as perspiration evaporates off your skin. But on extremely hot days, evaporation slows and your body has to work harder to maintain a normal body temperature. The American Meteorological Society estimates that up to 1,000 people die each year from heat-related illnesses; many others become ill from heat exhaustion or heat stroke.

Viewer Tip: These tips will help you stay cool when the weather heats up.

Stay inside if possible. If you do not have air conditioning at home, go to the home of a friend or relative, shopping mall, public library, cooling center or another public place. Even a few hours spent in air conditioning can help prevent heat-related illnesses.
While electric fans do have a cooling effect, they do not prevent heat-related illnesses when temperatures reach the high 90s. Taking a cool shower or bath or moving to a place that is air-conditioned are better choices.
Everyone feels the heat, but some people are more vulnerable to heat-related illnesses. Check regularly on friends and relatives who are 65 or older, have a mental illness, or have physical illnesses like heart disease or high blood pressure. Always keep a close watch on infants and children.

Season: Summer

(Sources: American Red Cross. “Talking about Disaster: Guide for Standarad Messages.” Available from: www.redcross.org.
Centers for Disease Control. “Tips for Preventing Heat-Related Illness.” http://emergency.cdc.gov/disaster/extremeheat/heattips.asp)

Heat Island Intensity

espinoza — Thu, 27 May 2010 15:05:28 +0000

Urban heat islands form as vegetation is replaced by asphalt, concrete and other “hard” surfaces for infrastructure like roads and buildings. These surfaces absorb rather than reflect incoming heat from the sun, causing overall urban temperatures to rise. Rising temperatures increase demand for energy for air conditioning, contribute to the creation of ground-level ozone air pollution and impact our health. Recently, NASA researchers studying urban heat islands found that the type of vegetation that existed in an area before city streets and buildings appeared makes a difference in how much heating occurs – cities built in forested areas show more heating than cities built in dry, desert-like areas. Temperatures in cities like Las Vegas or Phoenix, which replaced desert, are actually lower than surrounding natural areas. Temperatures in cities like Baltimore and Atlanta, which replaced forested land, are higher.

Viewer Tip: Paved driveways, sidewalks and patios can reach up to 150 degrees Fahrenheit during summer, but new “cool” pavement techniques can help reduce the amount of heat these surfaces absorb. Using grass pavers or concrete lattices for walkways allows grass to grow in spaces between the bricks; water evaporation from the grass has a cooling effect. There are also a variety of brick pavers available in colors and materials that are designed to reflect, rather than absorb, sunlight.

Season: Summer

(Sources: NASA/Goddard Space Flight Center (January 2010). Ecosystem, vegetation affect intensity of urban heat island effect; US Environmental Protection Agency. (October 2008) “Reducing Urban Heat Islands: Compendium of Strategies.” http://www.epa.gov/heatisland/resources/compendium.htm)

Thermal Pollution

administrator — Mon, 27 Jul 2009 12:22:06 +0000

Thermal pollution and thermal shocks are caused by increasing or lowering the temperature of water, which can harm aquatic life. Many aquatic animals depend on a particular temperature to reproduce and survive, and they can die even if temperatures change even slightly. Warmer water can also decrease dissolved oxygen levels, making it difficult for some species to survive. One source of thermal pollution is rain water runoff that warms up as it travels over hot driveways, sidewalks and streets. When pavement reaches a temperature of 100 degress Fahrenheit, it can raise the temperature of rain water runoff by as much as 25 degrees! The warm water eventually makes it into storm drains which lead directly to local streams and rivers in many communities.

Viewer Tip: Asphalt, tar and other dark pavement materials absorb and hold heat, even after the sun sets. If you are thinking about adding or replacing a walkway or driveway at your home, consider using materials that are less likely to absorb heat, such as gravel, grass, or mulch. Not only will these materials stay cool, but they’ll also allow rain water to soak into the ground instead of running off into the street.

Season: Summer

(Sources: Environmental Science: A Global Concern, Cunningham & Cunningham, 2007; NASA. “Coastal Cities Turn Up the Heat on Rainfall.” http://www.nasa.gov/centers/goddard/news/topstory/2003/0523urbanrainfall.html; US Department of Agriculture)

Heat and Age

administrator — Fri, 10 Jul 2009 12:17:35 +0000

“Heat islands” around urban areas form as vegetation is replaced by asphalt and concrete for roads, buildings and other infrastructure. These hard, dark surfaces absorb rather than reflect incoming heat from the sun, causing overall urban temperatures to rise. During hot weather spells, the heat island effect can raise urban temperatures by two to ten degrees Fahrenheit over those in nearby rural areas.

Viewer Tip: Older individuals are especially vulnerable to heat-related illnesses. The body’s cooling mechanism doesn’t work as efficiently as we age and living alone or being confined to a bed can further increase vulnerability to high temperatures. Keep these tips in mind to help older family members and friends stay healthy:

Seek out A/C – Just a few hours per day in an air-conditioned building can reduce risk of illness. If your home does not have A/C, visit a senior center, movie theater, library, mall or designated community cooling center. A fan may provide some relief, but when temperatures reach the high 90’s, electric fans do not prevent heat-related illness.
Dress the Part – Wear light-weight, loose clothing that is light in color. Drink plenty of fluids and avoid drinks with caffeine, alcohol or lots of sugar, which can cause dehydration.
Check Up – If you have a family member, friend or neighbor who is at risk, visit them regularly. If you see signs of heat-related illness – confusion, hot and dry skin, hallucinations, or aggression – seek help immediately.

Season: Summer

(Sources: Weather and Health, an online course developed by NEEF and the COMET Program. Access it free online: www.meted.ucar.edu/bmet_training.php; US EPA. October 2007. “It’s Too Darn Hot – Planning for Excessive Heat Events.” Publication number: EPA 100-F-07-025, www.epa.gov/aging)

Cool Roofs

administrator — Thu, 19 Feb 2009 15:28:40 +0000

Did you know that more than 90 percent of roofs in the U.S. are dark-colored? Dark colors absorb and hold on to heat from the sun, rather than reflecting it. This means that at midday during the summer, dark roofing materials can warm up to between 150 and 190 degrees Fahrenheit! A hot roof can contribute to increased energy use for air conditioning, higher demand for electricity, and reduced comfort indoors.

Viewer Tip: According to EPA, reflective “cool” roofing materials are often comparable, or even less expensive, that traditional roofing materials. And, when energy savings are factored in over the life of a cool roof, they can actually pay for themselves! Cool roofing materials can be used in new construction or when replacing a roof on older buildings. Homeowners have a couple options:

Reflective tiles are usually made of clay or concrete, and reflect between 10-30 percent of the sun’s energy. Some manufacturers are now able to produce tiles that reflect up to 70 percent of the sun’s energy, but still have traditional colors – brown, green, terra cotta – to eliminate the tradeoff between aesthetics and performance.
Metal roof products, which reflect radiation from the sun, are also available for residential use. Some manufacturers have developed metal roofs that reflect infrared radiation, keeping the materials even cooler!

Learn more about cool roofing materials at EPA’s Cool Roof Product Information website: www.epa.gov/hiri/strategies/level3_roofproducts.html.

Seasons: Summer, Fall

(Sources:US EPA, Heat Island Reduction Initiative. “Cool Roofs,” http://www.epa.gov/hiri/strategies/coolroofs.html, and “Cool Roof Product Information,” http://www.epa.gov/hiri/strategies/level3_roofproducts.html.)

Shade – A Savior!

administrator — Thu, 19 Feb 2009 13:38:51 +0000

During the heat of summer, shade from trees helps cool us and our homes. Trees can also pay dividends by shading our streets, which keeps pavement in better condition. Shaded streets require less maintenance and can save up to 60 percent on repaving costs over a 30-year period! Shade from trees also cools pavements, lessening the urban heat island effect that makes metropolitan areas considerably warmer than nearby rural areas.

Viewer Tip: Consider planting a tree near the edge of your property to shade your street and sidewalk. Make sure to choose a tree that will work well with the features of your property. Choose smaller trees for planting near power lines, and avoid using shallow-rooted species, which can heave sidewalks. As a general rule-of-thumb, plant trees at least three-feet from paved areas. Your local University Cooperative Extension office, garden center, or home improvement center can help you choose the right tree for your yard. You can also contact American Forests at www.americanforests.org for more information on how to get involved in urban tree plantings.

This Earth Gauge message was developed by American Forests, the nation’s oldest citizens’ conservation non-profit organization. American Forests is devoted to building a healthier world with trees.

Season: Summer

(Source: Alliance for Community Trees. “Why Shade TreesThe Unexpected Benefit.” http://actrees.org/site/stories/why_shade_streets_the_unexpected_benefit.php?tag=news.)

Heat and Health

administrator — Thu, 07 Aug 2008 15:30:00 +0000

In an average summer in the U.S., about 1500 people die from excesssive heat events. Excessive heat may disproportionately affect people in cities, where paved roads, buildings, and other “hard” surfaces absorb and trap heat from the sun. This “urban heat island effect” means that cities do not cool down at night like rural areas do, offering less relief from high temperatures during the nighttime hours.

Viewer Tip: Older adults are at increased risk for developing heat-related illnesses. As we age, our body’s cooling mechanism doesn’t work as efficiently, and living alone or being confined to a bed can further increase vulnerability to high temperatures. Individuals without air conditioning who live on top floors of buildings are likely to be exposed to excessive heat, and certain medications and medical conditions can increase risk. Keep these simple tips in mind to cope with the heat:

Air conditioning is one of the best protectors against heat-related illnesses – just a few hours per day in A/C can reduce risk of illness. If your home does not have air conditioning, visit a senior center, movie theater, library, mall, or a designated community cooling center.
A fan may provide some relief, but when temperatures reach the high 90’s, electric fans do not prevent heat-related illness.
Wear light-weight, loose clothing that is light in color. Drink plenty of fluids, and avoid drinks with caffeine, alcohol, or lots of sugar, which can cause dehydration.
If you have a family member, friend, or neighbor who is at risk, visit them at least twice per day. If you see signs of heat-related illness – confusion, hot and dry skin, hallucinations, or aggression – seek help immediately.

Season: Summer

(Sources: US EPA. October 2007. “It’s Too Darn Hot – Planning for Excessive Heat Events.” Publication number: EPA 100-F-07-025, www.epa.gov/aging)

Hot Dogs

administrator — Wed, 06 Aug 2008 18:49:22 +0000

Did you know that the temperature inside a car can rise by up to 40 degrees in one hour, even when outdoor temperatures are as low as 72 degrees Fahrenheit? When the sun shines on car windows, they collect light and trap heat inside the vehicle, raising temperature quickly. And, as the outdoor temperature rises, the effect becomes more pronounced. The inside temperature of a car can reach 102 degrees in ten minutes on an 85 degree day, and on hot and humid days, cars parked in direct sunlight can warm up by 30 degrees per minute.

Viewer Tip: Pets are even more susceptible to overheating than humans are – dogs’ sweat glands, which are located on their noses and pads of their feet, are inadequate for cooling off on hot days. And, just like humans, certain pets are more sensitive to heat: short-nosed breeds, older or very young pets, and animals with weight, respiratory, or heart problems. Many people are inclined to take pets along on summer travel or errands, but summer heat can be deadly for companion animals. If you’re headed to a place where pets may not be allowed, leave them at home with plenty of water and shade, instead of leaving them in the car.

Season: Summer

(Stanford School of Medicine, July 2005. “Parked Cars Get Dangerously Hot, Even on Cool Days, Stanford Study Finds.” med.stanford.edu/news_releases/2005/july/hot-cars.htm; Humane Society of the United States. “Cool It! Summer’s Heat can be Deadly for Your Pet.” www.hsus.org/pets/pet_care/cool_it_summers_heat_can_be_deadly_for_your_pet.html)

Shade – A Savior!

administrator — Wed, 06 Aug 2008 18:39:57 +0000

You can also contact American Forests at www.americanforests.org/ for more information on how to get involved in urban tree plantings.

(Source: Alliance for Community Trees. “Why Shade TreesThe Unexpected Benefit.” http://actrees.org/site/stories/why_shade_streets_the_unexpected_benefit.php?tag=news.)

The Heat is On

administrator — Thu, 24 Jul 2008 14:50:09 +0000

Did you know that the human body has about three million sweat glandsSweating cools your body when water on the skin is removed by evaporation. Unfortunately, when hot weather is coupled with high relative humidity, your body’s cooling system doesn’t work as well because humidity slows evaporation. Other factors also impact your body’s ability to cool, including sunburn, weight, age, dehydration, heart disease, poor circulation, and the effects of certain medications.

Viewer Tip: Hot weather can put extra stress on your body. When the temperature rises, keep these simple tips in mind to beat the heat:

Take it Slow: Reschedule outdoor exercise and other strenuous activities for the coolest times of day - early morning or evening – and spend time in air-conditioned buildings.
Dress Appropriately: Light colors and lightweight fabrics reflect heat and sunlight, helping to keep you cool.
Drink Plenty of Water: Water helps keep your body cool.
Lend a Hand: Infants and young children (up to four years old) are especially sensitive to heat. Older individuals (65 years and older) may not compensate for heat as efficiently as younger people, and are not as likely to sense or respond to changes in temperature. Check on family members and friends frequently to make sure they stay safe and healthy.

Season: Summer

(Sources: USA Today. “Sweating is one way to keep your cool.” May 20, 2005. http://www.usatoday.com/weather/resources/basics/sweating-cools.htm; NOAA National Weather Service. “Heat Wave: A Major Summer Killer.” Available from: http://www.weather.gov/os/heat/heat_wave.shtml; Centers for Disease Control: Extreme Heat. http://www.bt.cdc.gov/disasters/extremeheat/heat_guide.asp)

Buddy System Benefits (St. Louis, MO)

administrator — Thu, 30 Aug 2007 14:32:43 +0000

According to estimates based on the 1990 population, extreme heat events cause close to 2,000 deaths in the U.S. every year, and 79 of these deaths occur in the St. Louis Metropolitan Area. The elderly, infants, and people with disabilities or chronic illnesses, particularly those lacking air conditioning and transportation, and living alone, account for the vast majority of these deaths.

Viewer Tip: Help reduce heat-related deaths by lending a hand to neighbors and friends:

Identify high risk individuals (i.e. the elderly, disabled, chronically ill, and those with small children) in your neighborhood that may need assistance during a heat event.
Pay attention to your weather forecast. Warnings about extreme heat will be issued.
When extreme heat warnings are issued, check on high risk friends and neighbors and encourage them to seek shelter in air conditioned environments. Public shelters are available for this purpose, and many communities open cooling centers during heat waves. The United Way of Greater St. Louis Information & Referral Services (1-800-427-4626) can help find a shelter near you.

Season: Summer

(Sources: United States Environmental Protection Agency: Office of Atmospheric Programs. “Excessive Heat Events Guidebook.” Washington, DC. 2006 and Kalkstein, LS and Greene, JS. “An Evaluation of Climate/Mortality Relationships in Large U.S. Cities and the Possible Impacts of a Climate Change.” Environmental Health Perspectives Volume 105, Number 1, January 1997.)

Temperature Rising (Nashville, TN)

administrator — Thu, 30 Aug 2007 13:39:21 +0000

The National Weather Service uses the “Heat Index” to indicate how hot the weather feels to the body when temperature and humidity are taken into account. It is important to remember, however, that the values in the Heat Index are calculated for shady conditions – it can feel up to 15 degrees hotter in direct sunlight! Air pollution can also become a problem on hot days, when when pollutants from car exhaust, factories, and other sources react with heat and sunlight to create ground-level ozone pollution.

Viewer Tip: Nasvhille has experienced 20 consecutive days with temperatures 95 degrees or higher, beating the record of 19 days set in 1952! Pay attention to heat advisories and air quality reports in your area, and minimize the risks to your health during hot weather by following these tips:

Wear clothing that is both light in color and weight, but be careful not to wear clothing that can expose you to sunburn. Sunburned skin inhibits your body’s cooling abilities.
Drink plenty of water; avoid drinking alcohol and eating heavy meals.
Try to limit outdoor activities, or do these activities during the coolest parts of the day.
Seek shelter in an air conditioned environment, such as shopping malls and movie theaters. Doing so can reduce your risk of overheating.

Season: Summer

(Sources: National Weather Service. “JetStream: Heat Index.” http://www.srh.noaa.gov/jetstream/global/hi.htm; United States Environmental Protection Agency: Office of Atmospheric Programs. “Excessive Heat Events Guidebook.” Washington, DC. 2006 and Kalkstein, LS and Greene, JS. “An Evaluation of Climate/Mortality Relationships in Large U.S. Cities and the Possible Impacts of a Climate Change.” Environmental Health Perspectives Volume 105, Number 1, January 1997)

Handling Heat Stress (Louisville, KY)

administrator — Wed, 29 Aug 2007 18:20:30 +0000

According to estimates based on the 1990 population, extreme heat events cause close to 2,000 deaths in the U.S. every year; 17 of these deaths happen in the Louisville Metropolitan Area. If you lack air conditioning and live in an upper floor of a building, especially a building with a dark roof that is surrounded by dark pavement, you may be especially vulnerable to heat related illnesses.

Viewer Tip: Minimize the risks to your health during hot weather by following these tips:

Wear clothing that is both light in color and weight, but be careful not to wear clothing that can expose you to sunburn. Sunburned skin inhibits your body’s cooling abilities.
Drink plenty of water; avoid drinking alcohol and eating heavy meals.
Try to limit outdoor activities, or do these activities during the coolest parts of the day.
Seek shelter in an air conditioned environment, such as shopping malls and movie theaters. Doing so can reduce your risk of overheating.

Season: Summer

Temperature Rising

administrator — Tue, 28 Aug 2007 14:48:08 +0000

Viewer Tip: Kids tend to spend more time outside and perform more vigorous activities, such as running and outdoor sports, which can expose them to health risks from heat and poor air quality. Pay attention to heat advisories and air quality reports in your area, and when conditions are poor, consider rescheduling sports games and other outdoor activities for another day. If you do go outside, aim for early morning or evening hours, when temperatures and air pollution levels are likely to be lower.

Season: Summer

(Sources: National Weather Service. “JetStream: Heat Index.” http://www.srh.noaa.gov/jetstream/global/hi.htm; Asthma and Allergy Foundation of America. “Asthma Facts and Figures.” http://www.aafa.org/print.cfm?id=8&sub=42))

Urban Islands

administrator — Tue, 28 Aug 2007 14:46:06 +0000

In many U.S. cities, summertime temperatures can be up to 10 degrees warmer than surrounding natural areas, creating “urban heat islands.” The structure of cities plays a major role in the development of heat islands – dark pavement and buildings absorb and trap heat, narrow streets with tall buildings can trap heat and reduce wind flow, and reduced tree cover results in less shading and natural cooling. As a matter of fact, increasing temperatures in cities over the past several decades means that between three- to eight-percent of energy is used to compensate for the heat island effect

Viewer Tip: Stay cool and save energy by keeping your home closed up during the day and putting off any heat-producing activities (such as running the dishwasher or dryer) until the cooler evening hours. If you don’t have a fan or air conditioner, try to get to a mall, library, or other community building to cool off. And, lend a hand — if you have an older or disabled relative, friend, or neighbor, check-in with them to make sure they are safely coping with the heat.

Season: Summer

(Sources: US EPA. “Cooling Summertime Temperatures: Strategies to Reduce Urban Heat Islands.” http://www.epa.gov/heatisland/resources/pdf/HIRIbrochure.pdf; National Institutes of Health. “Keep it Cool with Hot Weather Advice for Older People.” www.nih.gov/news/pr/jul2006/nia-24.htm)

Turning Up the Heat

administrator — Tue, 28 Aug 2007 14:43:40 +0000

Did you know that urban heat islands – where pavement and buildings absorb and trap heat, making cities feel warmer than surrounding natural areas – can actually affect Houston’s weather patterns? Scientists have found that urban heat islands cause warm air to rise, and when this air reacts with sea breezes, it creates more frequent, heavier rainfall in the city! As a matter of fact, analysis of Houston’s rain gauge data both before and during urbanization shows increased rainfall as more heat islands formed in the city.

Viewer Tip: Asphalt, tar, and other dark pavement and roof surfaces absorb and hold heat, even after the sun sets. If you are thinking about adding or replacing a walkway at your home, consider using materials that are less likely to absorb heat, such as gravel, grass, or mulch. Not only will these materials stay cool, but they’ll also allow rain water to soak into the ground instead of running off into the street.

Season: Summer

(Sources: NASA. 2003. “Coastal Cities Turn Up the Heat on Rainfall.” http://www.nasa.gov/centers/goddard/news/topstory/2003/0523urbanrainfall.html; US Department of Agriculture)

Nighttime Heat

administrator — Tue, 28 Aug 2007 14:42:33 +0000

Pavement and buildings in cities absorb and trap heat, and temperatures can be several degrees warmer in the city than surrounding natural areas. At night, these “hard” surfaces gradually release stored heat and raise night time temperatures, offering little relief during hot weather events.

Viewer Tip: Asphalt, tar, and other dark pavement and roof surfaces absorb and hold heat, even after the sun sets. Thinking about adding or replacing a walkway at your homeConsider using materials that are less likely to absorb heat, such as gravel, grass, or mulch. Not only will these materials stay cool, but they’ll also allow rain water to soak into the ground instead of running off into the street.

Season: Summer

(Sources: US EPA. “Cooling Summertime Temperatures: Strategies to Reduce Urban Heat Islands.” http://www.epa.gov/heatisland/resources/pdf/HIRIbrochure.pdf)

Urban Islands

administrator — Mon, 06 Aug 2007 19:28:20 +0000

Season: Summer

Urban Heat Islands: Trapped!

administrator — Mon, 23 Jul 2007 18:49:49 +0000

Urban heat islands, created when pavement, driveways, and other surfaces absorb and trap heat in cities, can intensify hot weather and increase the amount of ozone pollution in the air.

Viewer Tip: Gas-powered vehicles contribute to ozone pollution. On hot days, consider reducing your driving time by carpooling, using public transportation, or walking to your destination.

Seasons: Summer

(Source: United States Environmental Protection Agency. 2004. “Cooling Summertime Temperatures: Strategies to Reduce Urban Heat Islands.” Publication Number 430-F-02-014.)