0 5 10 15 20 25 30 35 40 45 50 550.0

0.2

0.4

0.6

0.8

1.0

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.