What is the main topic of this news? [originaltext] Scientists say that night

Scientists say that nighttime flights are much more damaging to the environment than daytime air travel. In new research published in journal Nature, they say vapor trails produced by aircrafts do far more damage during the night. The reason is condensation water vapor emitted from hot engine of aircraft condensing into trailing clouds. Our science reporter M. G. has more. "The scientists say that in daylight the trails act like mini-clouds. They are good for the environment because the white color deflects the Sun’s rays and reduce temperature. At night from the sun goes down this positive benefit is lost. The impact of night travel is surprisingly large. In the United Kingdom only a quarter of flight takes place in darkness. But this accounts for up to 80% of greenhouse effect from condensation."