No, they're not. Otherwise they would always be seen.
According to the ICAO . . .
The International Standard Atmosphere at mean sea level is a temperature of +15ºC (59ºF) at a Pressure of 1013.2mb (29.92 InHg) decreasing by 1.98ºC (35.564ºF) per 1000 feet of increased altitude.
However, at the tropopause, the temperature remains constant at -56.5ºC (-69.7ºF). The height of the tropopause varies all the time but it is USUALLY around the 36,000 ft mark - depending on time of year and the latitude (higher near the equator than the poles).
I love it when I see one plane doing a contrail and another doing a chemtrail at roughly the same altitude. Also love it when they run out of aerosol and then turn around and go home and the trail stops dead.
No, they're not. Otherwise they would always be seen.
According to the ICAO . . .
The International Standard Atmosphere at mean sea level is a temperature of +15ºC (59ºF) at a Pressure of 1013.2mb (29.92 InHg) decreasing by 1.98ºC (35.564ºF) per 1000 feet of increased altitude.
However, at the tropopause, the temperature remains constant at -56.5ºC (-69.7ºF). The height of the tropopause varies all the time but it is USUALLY around the 36,000 ft mark - depending on time of year and the latitude (higher near the equator than the poles).
I love it when I see one plane doing a contrail and another doing a chemtrail at roughly the same altitude. Also love it when they run out of aerosol and then turn around and go home and the trail stops dead.