1 High latitude, deep, and thermohaline circulation October 15.
Impact of a thermohaline circulation slowdown
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Transcript of Impact of a thermohaline circulation slowdown
Shutting down the thermohaline circulation
David AnthoffUniversity of California, Berkeley
Francisco EstradaUniversidad Nacional Autónoma de Mexico
Richard S.J. TolUniversity of Sussex, Vrije Universiteit
Amsterdam, Tinbergen Institute, CESifo
Key concern• Climate change could lead to• More rain over the North Atlantic• Melting of the Greenland Ice Sheet
• This would lead to a drop in salinity and may slow-down – or even shut-down – the thermohaline circulation
WE FEAR THE COLD
-25.0
-22.5
-20.0
-17.5
-15.0
-12.5
-10.0
-7.5
-5.0
-2.5
0.0
2.5
5.0
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
Wel
fare
-equ
ival
ent i
ncom
e ch
ange
(in
perc
ent)
Global warming (in degrees centrigrade)
-20
-15
-10
-5
0
5
10
100 1,000 10,000 100,000
Wel
fare
-equ
ival
ent i
ncom
e ch
ange
(in
perc
ent)
Income (in 2005 dollar per person per year)
-25.0
-22.5
-20.0
-17.5
-15.0
-12.5
-10.0
-7.5
-5.0
-2.5
0.0
2.5
5.0
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
Wel
fare
-equ
ival
ent i
ncom
e ch
ange
(in
perc
ent)
Global warming (in degrees centrigrade)
Fit same function per country:
Optimum temperature:0.3K, range -3 - +7K above today
Slopes vary from zero to 28%Y/K
Hosing• Coupled atmosphere-ocean general
circulation models project a slight weakening of the thermohaline circulation• The impact of a more drastic weakening
are studied using so-calling hosing experiments, in which a Death Star suddenly appears to spout freshwater into the North Atlantic
-6
-5
-4
-3
-2
-1
0
1te
mper
atur
e cha
nge (
degr
ee ce
ntigr
ade)
Hadley 0.3Hadley 0.1BCM 0.1IPSL 0.1
-7
-6
-5
-4
-3
-2
-1
0
1
-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
Welf
are ga
in (%
incom
e)
Warming (degree centigrade)
Modest warming dueto greenhouse gases,severe cooling duetothermohaline circulationshutdown
Severe warming dueto greenhouse gases,modest cooling duetothermohaline circulationshutdown
-4
-2
0
2
4
6
8w
elfa
re im
pact
(per
cen
t inc
ome)
Hadley 0.3Hadley 0.1BCM 0.1IPSL 0.1
-10
-8
-6
-4
-2
0
2
4
6
8we
lfare
impa
ct (p
er ce
nt in
come
)
Hadley 0.3Hadley 0.1BCM 0.1IPSL 0.1
Wrap-up• Warming is bad, cooling is worse• The cooling due to a shut- or slowdown of
the thermohaline circulation is modest relative to the warming that would induce that.• Reduced warming would lead to a welfare
gain in most countries