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Seeing Green

Who Are NASA's Earth Explorers?

The elementary school student wondering how El Niño will affect tomorrow's weather. The scientist studying connections between ozone and climate change. And the farmer using satellite pictures to keep track of crops. All of these people are Earth Explorers -- they are all curious about the Earth system. This series will introduce you to NASA Earth Explorers, young and old, with many backgrounds and interests.

A fear of heights may be a problem for gardeners of the future. Scientists and students are studying the benefits of green roofs on buildings high and low. A green roof is a roof covered with plants and other vegetation.

The hypothesis is that green roofs could cool urban heat islands. These are places where the temperature is often warmer than surrounding areas. Most major cities are urban heat islands because they have a lot of asphalt and cement. These materials absorb more heat than grass and trees.

NASA scientists want to know the pros and cons of green roofs. They are working with community groups in the New York City area to build green roofs and study them. New York City has a lot of buildings and a lot of roofs.

"We're trying to be like the Johnny Appleseed of New York for green roofs," said Stuart Gaffin, a NASA scientist. "We're just trying to get them going here and there."

Jason stands in front of a statue that looks like a crab
Image to right: Jason records temperatures in New York City. Credit: NASA GISS

Jason, 16, is helping out with the project this summer. He's been all over the Big Apple. His job has been to measure the temperature of different kinds of surfaces. These surfaces include roofs and walls, streets and sidewalks, and grass and leaves.

"I've had to take scientific data before, just not like a scale so intense and detailed," Jason said.

The temperature and other weather data go into a climate model. Adam Greenbaum is running the model this summer. He's a student at Brown University. The model simulates how energy moves in and out of a roof and other surfaces. It's the kind of thing that has interested Greenbaum since he was a kid, thanks in part to his physicist dad.

"Ever since I was really little, he was explaining things to me," Greenbaum said. "It kind of instilled a curiosity in me."

Gaffin hopes the model results will answer some questions about green roofs. Building owners and other people want to know if green roofs are worth their higher price. They can cost as much as double a normal roof.

One study has already shown that green roofs can be more than 50 degrees cooler than dark roofs. What makes green roofs so much cooler? For one thing, they are lighter in color. This lighter color reflects more sunlight than other roofs. Also, plants use nearby heat to evaporate water. This goes toward cooling the roof as well.

Green roof supporters say the benefits could go beyond cooling, though. Other perks may include lower heating and cooling costs and roofs that last longer. Green roofs may also improve air quality. And they may reduce the amount of pollution in water.

"The benefits are both public and private," Gaffin said.

Adam Greenbaum sitting at a computer
Image to left: Adam Greenbaum runs a computer model. It's the kind of thing he has always been interested in. Credit: NASA GISS

Jason and Greenbaum are taking part in the green roofs study through a special program. It's called the New York City Research Initiative and is sponsored by NASA. The program teams students and scientists together to work on NASA projects. Besides doing research, students go to meetings and lectures. And they present oral reports and visit science labs and museums.

Gaffin has the help of Jason and Greenbaum only through the end of the summer. But he plans to make use of their work long after they head back to school in the fall. There are still many research questions to be answered. Gaffin wants to know how green roofs can be designed to produce optimal cooling. And he wants to figure out what kind of insulation value they have.

It's the kind of work that makes becoming a scientist worth the hard challenges. At least that's what Greenbaum says.

"If you find science fulfilling and you're really interested in it, then going through the hardship of learning the math and the concepts isn't that difficult," he said. "There's something at the end that's worth getting to."

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New York City Research Initiative
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Dan Stillman, Institute for Global Environmental Strategies