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Studying clouds may seem like an idle pastime, but the practice has gained a new sense of urgency in the era of global warming.

That is because some types of clouds act to cool the planet while others help to warm it. So, scientists are having trouble making accurate predictions of human-induced climate change while taking into account effects of natural cloud formations.

Today, however, scientists hope to gain a better understanding of global cloud patterns with the launch of two new U.S. research satellites: CloudSat and Calipso.

They were to be blasted into orbit early this morning from Vandenberg Air Force Base on California's central coast.

CloudSat is packed with Canadian-built scientific instruments, which will provide unprecedented radar images of the interior of clouds.

"We want to be able to develop better representations of cloud in models . . . for predicting climate change," said Réjean Michaud, director of atmospheric sciences at the Canadian Space Agency, a joint partner in the U.S.-led mission.

He noted that existing satellites show just the tops of clouds, while ground-based observations primarily focus on the bottoms.

CloudSat, on the other hand, should provide the first 3-D images of clouds on a global scale. The satellite is equipped with special radar to "see" inside clouds, providing data on their overall size and how much water and ice they contain. Essentially, the satellite will create "vertical profiles" of clouds as it orbits 705 kilometres above Earth.

Dr. Michaud said the mission would not be possible without the highly specialized instruments designed and built in Canada. A device that amplifies the radar signals was developed by CPI Canada Inc. in Georgetown, Ont. And a part that will receive the returning signals was produced by COM DEV International Ltd. in Cambridge, Ont.

He added that Canada has much to gain from its $17.5-million contribution, which is roughly 10 per cent of the total cost of CloudSat. "With improved climate models we stand a chance to have improved weather forecasts," he said, noting that northern regions have unique cloud patterns that are not well understood.

Calipso will gather data on aerosols, tiny particles around which moisture collects to form clouds.

The two satellites will fly just 93 kilometres apart, which works out to a time delay of 12.5 seconds. That means they will be observing the same clouds at almost the same time and their data can be combined to help answer questions about how clouds affect climate.

The new probes will be joining three existing satellites that are studying Earth's atmosphere and water resources. Together, they will form a string of satellites, nicknamed the A-Train. (The first satellite in the chain in called Aura; the last is Aqua.)

Researchers estimate that by the middle of this century, the amount of carbon dioxide in the atmosphere will have doubled since the beginning of the industrial revolution. Carbon dioxide acts as a greenhouse gas, trapping the sun's energy and warming the planet.

As the temperature rises, the atmosphere should be able to hold more moisture, thereby leading to additional cloud cover. The water vapour in clouds can also act as a greenhouse gas and further drive up the planetary thermostat.

But different types of clouds can have opposite climatic effects. High-altitude clouds tend allow in the sun's rays, but prevent this energy from radiating back. As a general rule, they form an insulating blanket. Low-altitude clouds block a significant portion of the sun's incoming radiation. Their overall impact is to cool the planet.