Norman Loeb studies clouds’ effect on Earth’s climate

Norman Loeb: We really don’t have a long enough reliable global data set to say what clouds are doing to the climate system.

Physical scientist Norman Loeb is a principal investigator of the NASA instrument called CERES, short for Clouds and the Earth’s Radiant Energy System, on board the Aqua and Terra satellites. Since 1999, CERES instruments have orbited the Earth via satellite.

Norman Loeb: They really are geared to capture all of the radiation that’s reflected or emitted from the planet.

That radiation is sunlight, said Loeb, reflected into space from the tops of clouds, the Earth’s surface, and atmospheric particles. The radiation also includes heat emitted from the Earth’s surface and atmosphere. Knowing how much energy leaves the Earth tells scientists a lot about global climate.

Norman Loeb: Earth’s climate is really driven by a delicate balance between how much of the sun’s energy is absorbed by the Earth as visible light, and how much the Earth emits to space in the form of infrared radiation.

The role of clouds in climate is complex and not well understood, said Loeb, because they both cool the planet by reflecting sunlight and keep it warm by trapping heat. So what will be the role of clouds as our climate warms?

Norman Loeb: Will a warmer climate reduce global cloud cover? Will it increase the height of clouds? Will it change the thickness of clouds? So all of these are important scientific questions that we’ll need to address.

Dr. Loeb talked more about the goals of the CERES mission.

Norman Loeb:The objective is to observe the Earth’s radiation budget, together with the clouds, and also, we have’t mentioned, the aerosols as well, which are important in this issue. Observing these and other atmospheric and surface properties over several years, and preferably over several decades, enables us to improve our understanding of how the climate system is changing and really provides an invaluable resource for testing climate models that are used to simulate future climate change.

Loeb spoke of some of the challenges of studying the effects of clouds on climate.

Norman Loeb: In terms of what evidence, in terms of the clouds and what they’re doing to climate right now, we really don’t have a long enough reliable global data set to say what clouds are doing to the climate system. There’s a lot of natural variability to the system, and to be able to tease out a significant change in clouds in such a short period is very difficult. So I think we need to keep measuring over long time scales and have the accuracy that’s needed as well, that’s the important thing.

Our thanks today to NASA’s Aqua Mission, improving our knowledge of our home planet through satellite observations.

November 30, 2009

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