J: joule. The energy of one watt of power flowing for one second

GJ: gigajoule, 109 joules

EJ : exajoule, 1018 joules

BTU: British thermal unit. The energy to raise the temperature of one pound of water one degree Fahrenheit.

quad: a quadrillion (a million-billion, or 1015 ) BTUs, equal to 1.055 × 1018 joules (1.055 EJ). A unit commonly used in discussing global and national energy budgets

W: watt, a unit of electric power (= 1 J of energy per second)

kW: kilowatt, a thousand (103 ) Watts

GW: gigawatt, a billion (109 )Watts

TW: terawatt, a trillion (1012) Watts

kWh: kilowatt-hour, or the amount of energy when one kW is used for one hour. Equivalent to about 3,400 BTU or 3,600,000 Joules

Metric ton (i.e., of CO2) is one thousand kilograms, or about 2,200 pounds

MMT: million metric tons of CO2

Mt: megaton, a million (106) metric tons

Gt: gigaton, a billion (109) metric tons

Tg: teragram, a billion (109)kilograms, or one million metric tons

ppm: parts per million, a measure of atmospheric concentration of some greenhouse gases

Barrel (oil): ~42 gallons. The United States uses about 20 million barrels of oil each day.

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