Getting to the Bottom of Global Warming — From Space

By Grace V. Jean
The first of several satellites designed to monitor Earth’s greenhouse gases has reached orbit and will begin collecting data in the coming months.

If all goes as planned, the Greenhouse Gases Observing Satellite for the next five years will track the amount of carbon dioxide and methane found in the planet’s atmosphere and record the behavior and distribution of those gases in certain geographical regions. 

The hope is that the data will illuminate how greenhouse gases are being emitted and absorbed by the Earth, which ought to help scientists determine what can be done to prevent global warming, says Takashi Hamazaki, the satellite’s project manager at the Japan Aerospace Exploration Agency.

Increasing levels of carbon dioxide have been blamed for causing climate change. The gas, which occurs naturally and also is produced by man-made technologies, surrounds the Earth like a blanket and prevents reflected sunlight energy from escaping into outer space. The trapped infrared light heats up the planet. 

Scientists believe that the world’s oceans, vegetation and soil absorb about half of the emitted carbon dioxide. But so far, they don’t have much empirical proof of this phenomenon because of limited data.

Greenhouse gas data is routinely collected by 280 ground observation stations scattered worldwide, but they are concentrated mostly around Europe, Japan and the United States. Airplanes also carry sensors into the skies to collect additional data. With so few collection points, the information is not as accurate as scientists would like.

The atmosphere’s carbon dioxide density dynamically changes, like a person’s respiration, and it varies in different parts of the globe. The ideal way to monitor these variations holistically is via observation from space, scientists say.

The 18 billion yen GOSAT, as the satellite is nicknamed, will orbit the planet every 100 minutes using sophisticated sensors to measure greenhouse gases over the planet’s entire surface at some 56,000 observation points. It can scan the entire globe in three days, Hamazaki says.

“I really hope to see the breathing of the Earth,” he writes from Japan in response to emailed questions from National Defense.

Two onboard sensors, the Thermal and Near-infrared Sensor for Carbon Observation-Fourier Transform Spectrometer and the Cloud and Aerosol Imager, will work in tandem to evaluate the density of greenhouse gases. They will measure the infrared light that is reflected at the surface. As the light passes through carbon dioxide and methane, specific wavelengths are absorbed. That absorption is directly proportional to the gases’ densities.

The average density of carbon dioxide in the Earth’s atmosphere is around 380 parts per million. With its sensors, GOSAT can detect minute changes, including shifts as small as one part per million — a difference of one one-millionth. That sensitivity is similar to the ability to discern four drops of solution in a bathtub filled with water.

Detecting changes in the density over the world’s oceans will help scientists better understand where and how much carbon dioxide is emitted and absorbed in the maritime environment. The team also hopes to attain better data on methane gas absorption and emission in areas with permafrost such as Siberia, and in rainforests such as the Amazon, says Hamazaki. 

During these first three months, the Japanese space agency plans to test the satellite hardware’s function. In the next three months, the team will calibrate the sensors and validate observation data, which will be compared with ground-based information. Engineers and scientists from a variety of agencies and countries in six months’ time will evaluate the satellite for performance and effectiveness. In the fall, basic observation findings will be released to the world’s scientists.

The team early next year plans to begin sharing the carbon dioxide and methane density data with the public.

GOSAT is designed to operate for five years. But Hamazaki says that the satellite has potential for a longer lifespan. It is carrying enough onboard fuel and component redundancies to last more than 10 years. The agency already has initiated a study for a follow-on mission, which is expected to start in 2014.

NASA late last month also was planning to launch its own carbon dioxide monitoring satellite, the Orbiting Carbon Observatory. Japan has agreed to exchange its satellite data with the agency’s scientists for mutual collaboration.

“We hope to extend cooperation with other agencies as much as possible,” says Hamazaki.
The European Space Agency plans to distribute both satellites’ data from an archive site. It is studying a future observation satellite of its own, named A-SCOPE.

Topics: Energy, Climate Change, Space

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