Sea level the warmer water expands. For at least the last 100 years, sea level has been rising at an average rate of about per year. Most of this rise can be attributed to the increase in temperature of the sea and the resulting slight thermal expansion of the upper of sea water. Additional contributions, as much as one-quarter of the total, come from water sources on land, such as melting snow and glaciers and extraction of groundwater for irrigation and other agricultural and human uses. Pilots can estimate height above sea level with an altimeter set to a defined barometric pressure.
Armstrong limit Armstrong limit The Armstrong limit or Armstrong's line is a measure of altitude above which atmospheric pressure is sufficiently low that water boils at the normal temperature of the human body. Humans absolutely cannot survive above this limit in an unpressurized environment. Above Earth, this begins at above sea level. The term is named after United States Air Force General Harry George Armstrong, who was the first to recognize this phenomenon. The relevant external pressure on the human body is 0.0618 atm, 6.3 kPa, 47 mmHg, or about 1 psi. At or above the Armstrong limit, exposed body fluids such