"Bulb temperature" refers to the temperature at which condensation occurs when air is cooled down. It is the temperature where the air becomes saturated with moisture and water droplets start to form. Full definition
How long can we survive a wet bulb temperature of 35 C? (rabett.blogspot.ru)
A sedentary person who is naked and in the shade will run into the same problem at a wet - bulb temperature of 92 degrees. (realclimate.org)
If so that would leave the albedo effect to push the wet bulb temperature up, and the carbon storage effect to provide long term cooling. (realclimate.org)