Adds mass to a quantity of air, more mass means that quantity of air can absorb more heat and hold on to that heat longer.
Ice crystals, like Palacegalleryration pointed out, work like tin foil in an oven. The crystals work like a blanket that reflects some parts of sunlight back to Earth instead of continuing out to space.
Because unlike water vapour in air, the ice crystals in the contrail reflect light (which is why we can see them) which causes a radiative forcing effect preventing infrared radiation leaving the earth, causing heating.
How does the water vapor affect the climate?
Adds mass to a quantity of air, more mass means that quantity of air can absorb more heat and hold on to that heat longer.
Ice crystals, like Palacegalleryration pointed out, work like tin foil in an oven. The crystals work like a blanket that reflects some parts of sunlight back to Earth instead of continuing out to space.
Because unlike water vapour in air, the ice crystals in the contrail reflect light (which is why we can see them) which causes a radiative forcing effect preventing infrared radiation leaving the earth, causing heating.
loads more information