<s>
A	O
transient	B-Application
climate	I-Application
simulation	I-Application
is	O
a	O
mode	O
of	O
running	O
a	O
global	B-Application
climate	I-Application
model	I-Application
(	O
GCM	O
)	O
in	O
which	O
a	O
period	O
of	O
time	O
(	O
typically	O
18502100	O
)	O
is	O
simulated	O
with	O
continuously-varying	O
concentrations	O
of	O
greenhouse	O
gases	O
so	O
that	O
the	O
climate	O
of	O
the	O
model	O
represents	O
a	O
realistic	O
mode	O
of	O
possible	O
change	O
in	O
the	O
real	O
world	O
.	O
</s>
<s>
This	O
may	O
be	O
contrasted	O
with	O
an	O
equilibrium	B-Application
climate	I-Application
simulation	I-Application
in	O
which	O
greenhouse	O
gas	O
concentrations	O
are	O
suddenly	O
changed	O
(	O
typically	O
from	O
pre-industrial	O
values	O
to	O
twice	O
pre-industrial	O
values	O
)	O
and	O
the	O
model	O
allowed	O
to	O
come	O
into	O
equilibrium	O
with	O
the	O
new	O
forcing	O
.	O
</s>
<s>
Early	O
GCMs	B-Application
used	O
"	O
swamp	O
"	O
or	O
"	O
slab	O
"	O
ocean	O
models	O
for	O
reasons	O
of	O
computational	O
simplicity	O
.	O
</s>
