Climate Change Report Calls for More Aerosol Data Gathering

SAN FRANCISCO
— A new report on global climate change calls for a concerted effort to gather data on microscopic particles suspended in the Earth’s atmosphere and highlights the importance of space-based sensors like the Aerosol Polarimetry Sensor scheduled for launch in June aboard the NASA Glory climate-monitoring satellite.

In the report, “Atmospheric Aerosol Properties and Climate Impacts,” published Jan. 16 by the U.S. Climate Change Science Program, the authors say a network of sophisticated satellite, ground and airborne sensors designed to measure the quantity of atmospheric particles being produced by human activity will provide critical data to improve climate change models.

Climate change studies already provide detailed information on how greenhouse gases contribute to global warming. There is great uncertainty, however, about the complicated role aerosols, or tiny solid or liquid particles suspended in air, play in climate change, according to the report whose authors included scientists from NASA, the National Oceanic and Atmospheric Administration and the Department of Energy.

While natural particles from dust, volcanoes, fires and sea salt are the most common aerosols, man-made aerosols produced by the burning of fossil fuels are prevalent near cities and industrial centers. Those aerosols have an important impact on climate because particles of various shapes and sizes may scatter, reflect or absorb sunlight. At the same time, aerosols play a role in atmospheric heating and cooling by changing the properties of clouds and altering precipitation patterns.

“Presently the impact of aerosols on the Earth’s climate is believed to be comparable to the impact posed by greenhouse gases,” Michael Mishchenko, Glory project scientist for NASA’s Goddard Institute for Space Studies in New York, said in written answers to questions. “Still, aerosols remain poorly measured and represent the largest uncertainty in our understanding of climate changes.”

In order to improve the scientific community’s understanding of aerosols, the climate change report cites the need for enhanced satellite sensors capable of measuring the global distribution of these particles and their properties, such as size and shape, to help researchers determine whether the particles are natural or man-made. Furthermore, the report’s authors say that to fully understand aerosols and their impact on climate, satellite-based sensors will need to monitor aerosols continuously for decades.

One sensor mentioned in the report, the Aerosol Polarimetry Sensor (APS) built by Raytheon Space and Airborne Systems of El Segundo, Calif., is scheduled for launch June 15 on the Glory satellite. The APS, a multiangle, multispectralpolarimeter, is the first satellite instrument specifically designed to address the complexity of aerosol measurements from space, Mishchenko said.

The measurement of aerosols is of critical importance to climate studies, yet NASA’s attempts to fly aerosol polarimeters have encountered numerous obstacles in the past. An aerosol polarimeter was originally included in the Earth Observing System (EOS), but that sensor was dropped from the program. NASA also scrapped plans to include an aerosol monitoring instrument on the National Polar-orbiting Operational Environment Satellite System scheduled for launch in 2012. Even the Glory mission, now heralded as an important step forward in climate research, was dropped from the NASA budget in 2005, before being reinstated months later due to congressional pressure.

Now, NASA and Raytheon are preparing for Glory’s launch. The APS has completed vibration and electromagnetic compatibility testing and is performing well in thermal vacuum tests. Raytheon officials anticipate shipping the sensor in late February to the project management team at the
Goddard
Space
Flight
Center
in
Greenbelt
,
Md.
, said Raytheon spokesman John Barksdale.

In addition to APS, the Glory satellite built by Orbital Sciences Corp. of
Dulles
,
Va.
, will carry the Total Irradiance Monitor, an instrument built by the Laboratory for Atmospheric and Space Physics in
Boulder
,
Colo.
, designed to measure the amount of energy radiating from the sun to the Earth, and a pair of cameras designed for cloud identification. The cameras were built by Ball Aerospace and Technologies of Boulder.

The climate change report notes that while the Glory mission will help scientists collect data on aerosols, additional space-based sensors are needed. The Moderate Resolution Imaging Spectro-radiometer flying on the EOS Terra and Aqua satellites, and Terra’s Multi-angle Imaging Spectral Radiometer, provide some information on aerosols. Those EOS satellites are approaching the end of their scheduled design lives.

“Timely follow-on missions to at least maintain these capabilities are important,” according to the report. The report adds that more sophisticated sensors like APS will be needed to distinguish natural aerosols from atmospheric particles created by human activity.

“Now we recognize that studying aerosols from space with requisite accuracy and specificity is much more difficult than it had been stated,” Mishchenko said.

To further climate research, Mishchenko advocates sending an aerosol polarimeter into orbit as part of the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission. CLARREO, a joint NASA-National Oceanic and Atmospheric Administration mission cited in NASA’s Earth science decadal survey, is being studied by the two agencies. A decision whether to formally embark on the mission is expected by the end of the year, according NASA’s CLARREO mission webpage.

“An APS-type instrument is an ideal climate-monitoring instrument providing uniquely accurate and detailed information on aerosol, cloud and land surface characteristics and changes,” Mishchenko said. “We believe that it should be an integral part of a small dedicated climate-monitoring program such as the CLARREO mission.”