Tag Archives: UHI

Lead IPCC Author Warns of Extreme Heat Waves

National Public Radio’s Rachel Martin spoke recently with Michael Oppenheimer, the coordinating lead author of the synthesis report of the IPCC’s Fifth Climate Assessment.  During the interview, Oppenheimer noted that the urban heat island effect will become more of a threat in the years to come, warning that heat waves will become more frequent and more extreme…

MARTIN:  Up to this point, it’s been hard to pin down where the effects of climate change are going to be most profound.  Does this report tell us anything about specific places in the world that are especially at risk?

OPPENHEIMER: Well, I would first point to three types of places…

The third area I point to which effects people particularly in cities anywhere in the United States, which already have an urban heat island effect – well, I’d point to the extra frequency with which we’re getting already and are going to get more in the future – heat waves.  In Europe in 2003, about 40,000 people died in the heat wave.  We just can’t afford to have that risk increasing over time.  We’ve got to get on top of our missions or else it’s going to get out of control.

Oppenheimer closed by noting that we’re making progress in reducing greenhouse gas emissions, but that we’re not moving fast enough.  He described this report as a wake-up call to governments, noting that the opportunity to avoid a dangerous warming is disappearing.   The time to act is now.

You can listen to the full interview here.

Cool Roofs Are Cooling Homes in India

Climate change is driving up temperatures in cities around the world.  When things heat up, many of us simply reach for the thermostat and the air conditioner does its job.  In many parts of the world however, air conditioning isn’t an option and the rising temperatures mean homes become uninhabitable.   But there is a simple and affordable solution – a cool roof can bring down the temperature indoors by a few degrees, which is enough to allow people to sleep in their beds at night.

That’s where programs like the Cool Roof Project – through the Asian Cities Climate Change Resilience Network, and the Rockefeller Foundation – can help.  This program is installing cool roofs in Indore city, India, and residents are already getting relief from the urban heat.  From the Rockefeller Foundation

At Mamta Chouhan’s house, located in one of the 50 locations where cool roof technology has been implemented, a perceptible difference in indoor temperature is seen during high heat days.  The 200 families who have participated in this project have felt similar impacts as well.

Vijay Bhargava, a resident of Indore, reports that TARU came to him and others with an idea to reduce the temperature in their homes. “I didn’t believe it at first,” he admits, “but then they shared the details, including the potential benefits, and I changed my mind.  Afterwards, we felt a five or six degree change.  Incredible!”

He adds that he and his family couldn’t even sit upstairs in the summer before.  “Now, we can sit anywhere in the house, not feeling a difference whether we’re upstairs or downstairs.  It’s meant that we’ve been able to reduce our air conditioning usage substantially.”

They’re collecting data to document the many benefits of this program, and hope to convince local government, real estate developers and other interested parties to include cool roofs in future projects.   Stay tuned!

GCCA Executive Director Speaks at GreenBuild Conference

Thousands of people gathered in New Orleans, LA earlier this week for the annual Greenbuild conference, to share ideas, network, tour local green buildings and hear from many terrific speakers.  From the conference website:

Greenbuild is the world’s largest conference and expo dedicated to green building.  The green building community gathers to share ideals and mutual passion at Greenbuild, sparking a contagious buzz throughout the week.

When industry leaders, experts and frontline professionals dedicated to sustainable building in their everyday work come together, the result is a unique and palpable energy. Participants are invigorated and inspired.  They find themselves equipped to return to their jobs with a renewed sense of purpose.

GCCA Executive Director, Kurt Shickman spoke at this event about the many problems caused by the urban heat island effect, and the ways reflective surfaces can help bring relief to overheated city dwellers, reduce energy consumption, and reduce carbon emissions.  Take a look…

Los Angeles White Roofs Building Code is Online

Speaking of useful resources…

Last December, the Los Angeles City Council updated the city’s building code – which required the installation of white roofs on commercial structures – to require the installation of white roofs on new and rebuilt residential structures.  The city has put all the documents and discussion on line in their docket – including the City Attorney’s report.

Since then, several other cities (Pasadena and Hermosa Beach, CA) have enacted similar updates.  We thought it might be useful for other cities to have access to the relevant documents and reports, so we’ve added information on Los Angeles to our ToolKit Knowledge Base, which you can find HERE.

Study Shows How Increased Reflectivity Can Save Lives

Researchers at the Georgia Institute of Technology recently published a report, in which they took a look at past heat waves in Phoenix, AZ, Philadelphia, PA and Atlanta, GA.

This study shows that by adding white roofs, reflective pavement and trees, cities can counteract temperature increases in urban areas and save lives. From an article byClimateWire

[T]he researchers modeled how the three cities would respond to a minimum green space ratio on land parcels, setting a floor for areas covered with grass, gardens or trees. Vegetation tends to have a cooling effect by circulating moisture in the air that draws away heat during evaporation. Tree canopies also provide cooling shade.

The team also modeled how Phoenix, Philadelphia and Atlanta would behave with more reflective streets, sidewalks, parking lots and rooftops. Higher reflectivity, or albedo, means the area absorbs less sunlight, thereby lowering the temperature.

Stone and his collaborators then overlaid a health impact model.  They found that combinations of increased vegetation and albedo could cut into projected increases in heat deaths, reducing them between 40 and 99 percent. “On average, we reduced the rate of increase by about 60 percent,” Stone said.

Groups like the Global Cool Cities Alliance are now trying to get cities to adopt these adaptation strategies, pitching them as a way to protect public health. However, it’s slow going, given that cities around the country address heat vulnerability differently, if at all.

You can find the full study HERE.

This report parallels a recent GCCA report, which looks at Baltimore MD, New York, NY, and Los Angeles, CA, and shows how reflective roofs and vegetation can cool air temperatures and save lives.

Note: Access to the ClimateWire articles is limited to subscribers.

LBNL Develops New Interactive Rooftop Reflectance Map

Scientists at the Lawrence Berkeley National Laboratory (LBNL) have created an interactive map that displays the solar reflectance (or albedo) of individual roofs in five major California cities – Bakersfield, Long Beach, Los Angeles, San Francisco, and San Jose.   This is the first time scientists have attempted to map the reflectivity of entire cities.

A white / high-albedo cool roof reflects 80% of the sun’s heat, decreasing solar heating of the building. This reduces the need for air conditioning and lowers energy bills. Cool roofs could also partially counter increased urban temperatures brought on by climate change.

This map allows users to zoom in on a specific rooftop to see how it compares to the albedo of a white roof, or other roofs in the city, and is designed to help cities develop policies that could lead to cooler cities.

Ronnen Levinson, head of LBNL’s Heat Island Group and Board Member of the Global Cool Cities Alliance says this new map can be a useful tool for cities:

To assess these potential benefits for a particular city, we need to measure the reflectance of its roofs with good spatial and spectral resolution.  Our map helps bring this into focus.

You can explore LBNL’s new interactive map HERE.

Cool Roofs and Energy Efficiency in China

The Lawrence Berkeley National Laboratory (LBNL) has conducted the first comprehensive study of cool roofs in China and concluded that they would be an effective way to reduce energy use and greenhouse gas emissions.

Researchers ran simulations on residential and commercial buildings in seven cities in five climate zones, and found that light colored roofs reduced the need for air conditioning and energy consumption, and lowered the output of greenhouse gas trapping carbon dioxide.

LBNL scientist and lead author, Ronnen Levinson (member of GCCA’s Board) had this to say:

“Cool roofs have been well demonstrated in the United States, Europe, and elsewhere,” said lead author and Berkeley Lab scientist Ronnen Levinson. “While the concept is the same everywhere, we wanted to show that cool roofs would also be effective for Chinese construction, in Chinese climates, and with Chinese building operation practices.”

You can find the full study in the Toolkit’s Knowledge Base.

Cities Now Contain Over Half the World’s Population

Hot summer days can often be sticky and miserable in an urban heat island.  Dark surfaces, lack of shade trees and climate-driven heat events mean higher summer temperatures and prolonged heat waves.  Add to that the growing population in many of the world’s mega-cities, and winter weather is looking better and better!

The United Nations Department of Economic and Social Affairs Population Division just released their World Urbanization Prospects report for 2014.  Over half the world’s population are now living in urban settings.  Some of the reports key facts:

Globally, more people live in urban areas than in rural areas, with 54 per cent of the world’s population residing in urban areas in 2014. In 1950, 30 per cent of the world’s population was urban, and by 2050, 66 per cent of the world’s population is projected to be urban.

Today, the most urbanized regions include Northern America (82 per cent living in urban areas in 2014), Latin America and the Caribbean (80 per cent), and Europe (73 per cent). In contrast, Africa and Asia remain mostly rural, with 40 and 48 percent of their respective populations living in urban areas. All regions are expected to urbanize further over the coming decades. Africa and Asia are urbanizing faster than the other regions and are projected to become 56 and 64 per cent urban, respectively, by 2050.

Close to half of the world’s urban dwellers reside in relatively small settlements of less than 500,000 inhabitants, while only around one in eight live in the 28 mega-cities with more than 10 million inhabitants.

Combine these population trends with rising world temperatures, and it’s clear that urban heat island mitigation is becoming more and more urgent.

Projections of Increased Urban Heat May Have Been Underestimated

They say that location is everything in real estate, and when it comes to measuring urban heat, where you collect your data will have an impact on the accuracy of your results.

A new study out of London illustrates just how important it is to take certain variables into account if you want to get an accurate measurement of urban heat.  In this case, tracking night time urban heat in a park full of trees means that previous measurements may have underestimated the urban heat island effect by as much as 45 percent.

From Pys.orgLondon heat boost underestimated:

Until now, the effect has been measured by calculating the difference between temperatures in St James’ Park in the city, and Wisley – a rural site just outside the M25.

But new research, published in the journalScience of the Total Environment, found night time temperatures in parks can be up to 4°C cooler than in the streets nearby.  So the St James’ Park measurements might have dramatically underestimated the urban heat island in the capital.

‘In the summer time, built-up areas effectively act like a storage heater,’ says Dr Kieron Doick of Forest Research, the research agency for the UK Forestry Commission, who led the research. ‘They store up heat during the day and release it at night.’

‘The extra heat can pose a real health risk, so it’s important to understand the impact that planning decisions have on temperatures in our cities.’

The study mentioned in this article can be found at: