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Earth Systems Ecology&Biogeochemistry
Global Observations
Ecosystem Evolution Gradients
Global Change Experiments
Biogeochemical Models
Postdoc: Dr. Edith Bai
Graduate Student: Scott MorfordPostdoc: Dr. Tiffany van Huysen
Graduate Student: Alison Marklein
Colleague: Dr. YingPing Wang(CSIRO)
The Group
Not pictured: Undergraduates, Kim Mayfield, Ida Fischer, and Cheryl Higgins
How will nutrient limitation affect global warming?
CO2 Sink
CO2 Source
IPCC 4th Assessment Report
N2 fixation rate (g N m-2 year-1)
under the present climate condition
-150 -100 -50 0 50 100 150
Longitude (degree)
-50
0
50
Latit
ude
(deg
ree)
-1
1
3
5
7
9
11
Houlton et al., Nature, 2008
Nutrient limitation of CO2 uptake
-150 -100 -50 0 50 100 150
N (b lue) or P (red) lim iting for N PP
-50
0
50
Latit
ude
-0.0
5
-0.0
3
-0.0
1
0.01
0.03
0.05
Wang and Houlton, manuscript in preparation
The excess carbon in models used by the IPCC by year
2100
1 2 3 4 5 6 7 8
C p
ool i
ncre
ase
(Gt C
)
0
300
600
900
0
300
600
900
Model
Wang and Houlton, manuscript in preparation
N limitation increases warming
2100-1900: 0.66oC (C4MIP), 1.02 to 1.16oC (N limiting)
2100-1900
Model1 2 3 4 5 6 7 8
Add
ition
al w
arm
ing
(oC
)
0.0
0.5
1.0
1.5
2.0
2.5 Black: C4MIP results (no nitrogen limitation)
Red: N limitation (low N requirements)
Green: N limitation (high N requirements)
Wang and Houlton, manuscript in preparation
Conclusion
• Nutrient limitation of CO2 uptake is likely to play a major role in regulating earth’s future climate.
• The models used by the IPCC seem to underestimate global warming associated with elevated CO2 (by > 1 °C; ~ 2°F).
• IPCC must consider nutrient limitation in their next assessment.