Originally trained in Quaternary and glacial geology, my interests turned to oceanography after noting the profound influence of ocean heat transport on ice sheet growth and retreat in the Arctic. I was amongst the first to show that the timing and speed of changes in the large scale overturning circulation of the oceans matched that predicted by paleo-temperature records from Greenland ice cores and (the then) nascent numerical models of ocean circulation. In the run-up to the 1992 Rio Earth Summit (at which the United Nations Framework Convention on Climate Change was opened for signing) I gave testimony to the U.S. Senate warning that unmitigated warming could lead to changes in the overturning circulation of the northern North Atlantic—a phenomenon now clearly visible in regional air and sea temperatures 25 years later. For the last two decades my work has focused on studies of the ocean’s role in determining Ice Age (natural) CO2 variations and on the use of 14C as a tracer in the contemporary carbon cycle and for direct quantification of anthropogenic CO2 emissions.
- PhD: University of Colorado, 1989
- Postdoctoral Scholar: Woods Hole Oceanographic Inst/MIT Joint Program in Oceanography, 1987
The role of the oceans in climate change; cycling of heat, fresh water, and carbon by the oceans; dynamics and consequences of abrupt climate change; radiocarbon dating; 14C as a tracer in the carbon cycle.
Watch a 19-min video presentation on estimating US CO2 emissions
(CU-NOAA 14C-based Inverse Estimation of US CO2 emissions, EGU 2021)
2020: Basu, S., Lehman, S. J., Miller, J. B., Andrews, A. E., Sweeney, C., Gurney, K., Xu, X., Southon, J., Tans, P. P. Estimating US fossil fuel CO2 emissions from measurements of 14C in atmospheric CO2. Proceedings of the National Academy of Sciences, 117(24). doi 10.1073/pnas.1919032117
2016: Basu, S., Miller, J. B., Lehman, S. J. Separation of biospheric and fossil fuel fluxes of CO2 by atmospheric inversion of CO2 and 14CO2 measurements: Observation System Simulations. Atmospheric Chemistry and Physics, 16: 5665-5683. doi 10.5194/acp-16-5665-2016
2012: Miller, J. B., Lehman, S. J., Montzka, S. A., Sweeney, C., Miller, B. R., Karion, A., Wolak, C., Dlugokencky, E. J., Southon, J., Turnbull, J. C., Tans, P. P. Linking emissions of fossil fuel CO2 and other anthropogenic trace gases using atmospheric 14CO2. Journal of Geophysical Research—Atmospheres, 117(D8). doi 10.1029/2011JD017048
2007: Marchitto, T. M., Lehman, S. J., Ortiz, J. D., Flueckiger, J., van Geen, A. Marine radiocarbon evidence for the mechanism of deglacial atmospheric CO2 rise. Science, 316(5830): 1456-1459. doi 10.1126/science.1138679
2007: Turnbull, J. C., Lehman, S. J., Miller, J. B., Sparks, R. J., Southon, J. R., Tans P. P. A new high precision 14CO2 time series for North American continental air. Journal of Geophysical Research—Atmospheres, 112(D11). doi 10.1029/2006JD008184
2004: Hughen, K., Lehman, S., Southon, J., Overpeck, J., Marchal, O., Herring, C., Turnbull, J. C-14 activity and global carbon cycle changes over the past 50,000 years. Science, 303(5655) 202-207. doi 10.1126/science.1090300
2000: Hughen, K. A., Southon, J. R., Lehman, S. J., Overpeck, J. T. Synchronous radiocarbon and climate shifts during the last deglaciation. Science, 290(5498): 1951-1954. doi 10.1126/science.290.5498.1951
1993: Oppo, D. W., Lehman, S. J. Mid-depth circulation of the subpolar North Atlantic during the last glacial maximum. Science, 259(5098): 1148-1152. doi 10.1126/science.259.5098.1148
1992: Lehman, S. J., Keigwin, L. D. Sudden changes in North Atlantic circulation during the last deglaciation. Nature, 356(6372): 757-762. doi 10.1038/356757a0
For a full list of Scott's publications, see his Google Scholar profile.
- GEOL 5420: Quaternary Dating Methods
- GEOL 5700-011: Super-Problems in Quaternary Climate
- GEOL 5845-900: Independent Study, Geochemistry
- GEOL/ENVS 352: Environmental Issues in the Geosciences