1. Earth Systems Ecology & Biogeochemistry Global Observations Ecosystem Evolution Gradients Global Change Experiments Biogeochemical Models

2. Postdoc: Dr. Edith Bai Graduate Student: Scott Morford Postdoc: 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

3. How will nutrient limitation affect global warming? CO 2 Sink CO 2 Source IPCC 4 th Assessment Report

4. N 2 fixation rate (g N m -2 year -1 ) under the present climate condition Houlton et al., Nature, 2008

5. Nutrient limitation of CO 2 uptake Wang and Houlton, manuscript in preparation

6. The excess carbon in models used by the IPCC by year 2100 Model Wang and Houlton, manuscript in preparation

7. N limitation increases warming 2100-1900: 0.66 o C (C4MIP), 1.02 to 1.16 o C (N limiting) Black: C4MIP results (no nitrogen limitation) Red: N limitation (low N requirements) Green: N limitation (high N requirements) Wang and Houlton, manuscript in preparation

8. Conclusion Nutrient limitation of CO 2 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 CO 2 (by > 1 °C; ~ 2°F). IPCC must consider nutrient limitation in their next assessment.