Orbital decay
The decay in the height of an object's orbit over time due to the drag of the atmosphere on the object.  This drag increases during periods of high solar activity, due to more frequent collisions between the object and surrounding air molecules.

Osmotically active solutes
Polar solutes that associate with water through hydrogen bond formation.  The presence of such solutes effectively reduces the amount of free water in any system, thereby lowering its water potential.  As water moves along an increasingly negative water potential gradient, the presence of these solutes in cells can actually draw water into them.

Oxygen isotope analysis
A technique for inferring past temperatures of mediums, such as water, from the isotopic composition of oxygen incorporated into some type of fossil remains by a biological process in some organism, such as a diatom, in which the different isotopes of oxygen are utilized in different proportions at different temperatures.