The phrase "temperature differential" refers to the difference in temperature between two points or objects. It helps us understand how much the temperatures vary or how much one temperature is higher or lower than the other. Full definition
By preventing any persistent build up of temperature differential between air and water it also prevents any changes in air temperature affecting the temperature of the oceans and thereby changing the air temperature by indirect means. (newclimatemodel.com)
This develops a higher temperature differential across that gap, resulting in a hotter Earth's surface even though the radiating surface did not change temperature (in a suitably averaged sense). (judithcurry.com)
Even a small change in such a mechanism would dwarf by far any changes from most other sources and it appears that more warmth just accelerates it because of the increased temperature differential between surface and space. (newclimatemodel.com)