A、Ship traffic in the Atlantic. B、Warm currents in the ocean. C、Exhaust from cars in Europe. D、Particles emitted by power plants

A NASA satellite orbiting over Portugal took photographs that reveal the effects of pollution from ships. One of the photos shows a thin film of clouds above the brilliant blue of the North Atlantic, cut by white lines of thicker clouds that look like scars. NASA officials explained those thicker clouds are signs of ship traffic below. When ships power their way through the ocean, they pump exhaust into the atmosphere, just as cars do. And those massive amounts of particles can cause clouds to form. Get enough of those particles in one place, as from the exhaust of a ship, and they can lead to the creation of new clouds easily visible from space. "These clouds can be huge. Some of them stretch hundreds of kilometres from end to end," NASA officials said. It’s likely that these sorts of clouds are having some effect on the global climate, according to NASA officials. But scientists aren’t yet sure what effect it has.
1.  What has caused the thick clouds in the photos taken by a NASA satellite?
2.   What do NASA officials think about the thick clouds?