Vapour trails

Larry Dighera wrote:

Would that "opposite" be during the day or night? It also says: "...
nights warmer by trapping the Earth's heat."

Clouds reflect radiation wich results in cooler days and warmer nights.
The question is, what is the total effect (i.e. integrated over 24
hours). The article you cited says, the total effect will be a warmer
climate.

This said, and not having read the original paper, the weak point of
that paper is that it is the result of a singular event and as such, the
results cannot be reproduced. (Actually, they could...)

In general, the impact of clouds to the climate is mathematically very
difficult to model and is one of the last unresolved factors in climatology.

Stefan