Appendix VI  Units
SI (Systeme Internationale) Units:

Physical Quantity 
Name of Unit 
Symbol 

length 
metre 
m 
mass 
kilogram 
kg 
time 
second 
s 
thermodynamic temperature 
kelvin 
K 
amount of substance 
mole 
mol 


Fraction

Prefix

Symbol

Multiple

Prefix

Symbol


10^{1}

deci

d

10

deca

da

10^{2}

centi

c

10^{2}

hecto

h

10^{3}

milli

m

10^{3}

kilo

k

10^{6}

micro

µ

10^{6}

mega

M

10^{9}

nano

n

10^{9}

giga

G

10^{12}

pico

p

10^{12}

tera

T

10^{15}

femto

f

10^{15}

peta

P


Special Names and Symbols for Certain SIDerived Units:

Physical Quantity 
Name of SI Unit 
Symbol for SI Unit 
Definition of Unit 

force 
newton 
N 
kg m s^{2} 
pressure 
pascal 
Pa 
kg m^{1} s^{2} (=N m^{2}) 
energy 
joule 
J 
kg m^{2} s^{2} 
power 
watt 
W 
kg m^{2} s^{3} (=J s^{1}) 
frequency 
hertz 
Hz 
s^{1} (cycles per second) 

Decimal Fractions and Multiples of SI Units Having Special Names:

Physical Quantity 
Name of Unit 
Symbol for Unit 
Definition of Unit 

length 
Ångstrom 
Å 
10^{10 }m = 10^{8} cm 
length 
micron 
µm 
10^{6} m 
area 
hectare 
ha 
10^{4} m^{2} 
force 
dyne 
dyn 
10^{5} N 
pressure 
bar 
bar 
10^{5} N m^{2} = 10^{5} Pa 
pressure 
millibar 
mb 
10^{2} N m^{2} = 1 hPa 
mass 
tonne 
t 
10^{3} kg 
mass 
gram 
g 
10^{3} kg 
column density 
Dobson units 
DU 
2.687x10^{16} molecules cm^{2} 
streamfunction 
Sverdrup 
Sv 
10^{6} m^{3} s^{1} 


NonSI Units: 

°C 
degree Celsius (0 °C = 273 K approximately)
Temperature differences are also given in °C (=K) rather than the more
correct form of “Celsius degrees”. 
ppmv 
parts per million (10^{6}) by volume 
ppbv 
parts per billion (10^{9}) by volume 
pptv 
parts per trillion (10^{12}) by volume 
yr 
year 
ky 
thousands of years 
bp 
before present 


The units of mass adopted in this report are generally
those which have come into common usage and have deliberately not been harmonised,
e.g., 

GtC 
gigatonnes of carbon (1 GtC = 3.7 Gt carbon dioxide) 
PgC 
petagrams of carbon (1 PgC = 1 GtC) 
MtN 
megatonnes of nitrogen 
TgC 
teragrams of carbon (1 TgC = 1 MtC) 
Tg(CH_{4}) 
teragrams of methane 
TgN 
teragrams of nitrogen 
TgS 
teragrams of sulphur 

