Breadcrumb

Bio
My research interests are broad, but all revolve around the use of environmental stable isotope ratios.
I established and operated the Stable Isotope Laboratory for the analysis of stable isotope ratios of carbon, hydrogen, nitrogen, oxygen and sulfur. My specific areas of research include modeling the global carbon cycle using isotope ratios in atmospheric carbon dioxide and methane, development of techniques for measuring isotope ratios in atmospheric gases, reconstructions of paleo-environmental conditions using isotopes in ice cores, reconstructions of past environments from isotopes in organic materials, and tracing of ground water flow and recharge. I have been a member of several deep ice coring projects in Greenland (GISP2, NorthGRIP, and NEEM) and Antarctica (Siple Dome and Inland WAIS). I am also an affiliate of NOAA and work closely with the Carbon Cycle Group there.
Starting in the late 1980s, my ice core research has helped to show that large climate changes tend to occur in the natural system as abrupt and rapid shifts in mode probably driven by internal adjustments in the Earth climate system, rather than slow and gradual adjustments to changing external conditions, such as the amount of energy received from the sun. Shifts of more than 10˚C in mean temperature in less than a human lifetime are common in the paleoclimate record, and serve as a warning that adaptation to future climate changes may not be easy. My research in isotopes in the carbon cycle has also helped to show that land plants are capable of removing large amounts of carbon dioxide from the atmosphere, amounts that equal our input of CO2 from fossil fuel burning on short time scales. Such large changes in the uptake of CO2 by plants is a key piece in the puzzle we must solve to formulate workable policy on CO2 levels and climate change.
Education
- PhD: Columbia University, 1983
Awards
- Highly Cited Researcher (2016-2019), Web of Science Group, 2019
- Robert L. Stearns Award, CU Boulder Alumni Association, 2016
- Highly Cited Researcher, Thomson Reuters, 2014
- Fellow, American Association for the Advancement of Science, 2014
- Highly Cited Researcher, ISI, 2001
Research
Research interests: global scale climate and environmental dynamics; carbon dioxide concentrations and climate from stable hydrogen isotopes, peats and other organics; climate from deuterium excess and hydrogen isotopes in ice cores; isotopes in general circulation models; modern carbon cycle dynamics via isotopes of carbon dioxide and methane.
Publications
Recent publications
Land use effects on atmospheric C-13 imply a sizable terrestrial CO2 sink in tropical latitudes
Publication Date: 2002-05-15
Type: Journal Article
Simulation of stable water isotope variations by the GENESIS GCM for modern conditions
Publication Date: 2002-02-27
Type: Journal Article
Inter-annual variability of summertime CO concentrations in the Northern Hemisphere explained by boreal forest fires in North America and Russia
Publication Date: 2001-12-15
Type: Journal Article
NOAA/CSIRO Flask Air Intercomparison Experiment: A strategy for directly assessing consistency among atmospheric measurements made by independent laboratories
Masarie KA; Langenfelds RL; Allison CE; Conway TJ; Dlugokencky EJ; Francey RJ; Novelli PC; Steele LP; Tans PP; Vaughn B...
- Masarie KA
- Langenfelds RL
- Allison CE
- Conway TJ
- Dlugokencky EJ
- Francey RJ
- Novelli PC
- Steele LP
- Tans PP
- Vaughn B
Publication Date: 2001-09-16
Type: Journal Article
Oxygen isotope and palaeotemperature records from six Greenland ice-core stations: Camp Century, Dye-3, GRIP, GISP2, Renland and NorthGRIP
Johnsen SJ; DahlJensen D; Gundestrup N; Steffensen JP; Clausen HB; Miller H; Masson-Delmotte V; Sveinbjornsdottir AE; Wh...
- Johnsen SJ
- DahlJensen D
- Gundestrup N
- Steffensen JP
- Clausen HB
- Miller H
- Masson-Delmotte V
- Sveinbjornsdottir AE
- White J
Publication Date: 2001-05-01
Type: Journal Article
Holocene hydrological cycle changes in the Southern Hemisphere documented in East Antarctic deuterium excess records
Publication Date: 2001-04-01
Type: Journal Article
Multiproxy record of late Pleistocene-Holocene climate and vegetation changes from a peat bog in Patagonia
Publication Date: 2001-03-01
Type: Journal Article
ECMWF analyses and reanalyses depiction of ENSO signal in antarctic precipitation
Publication Date: 2000-04-15
Type: Journal Article
Entrainment at cold glacier beds
Publication Date: 2000-04-01
Type: Journal Article
Global carbon sinks and their variability inferred from atmospheric O-2 and delta C-13
Publication Date: 2000-03-31
Type: Journal Article
Measurement of O-18/O-16 in the soil-atmosphere CO2 flux
Publication Date: 1999-09-01
Type: Journal Article
A 3-dimensional study of delta O-18 in atmospheric CO2: contribution of different land ecosystems
Publication Date: 1999-07-01
Type: Journal Article
Determination of the isotopic (C-13/C-12) discrimination by terrestrial biology from a global network of observations (vol 12, pg 555, 1998)
Publication Date: 1999-03-01
Type: Journal Article
Seasonal variations of glaciochemical, isotopic and stratigraphic properties in Siple Dome (Antarctica) surface snow
Kreutz KJ; Mayewski PA; Twickler MS; Whitlow SI; White JWC; Shuman CA; Raymond CF; Conway H; McConnell JR...
- Kreutz KJ
- Mayewski PA
- Twickler MS
- Whitlow SI
- White JWC
- Shuman CA
- Raymond CF
- Conway H
- McConnell JR
Publication Date: 1999-01-01
Type: Journal Article
Palaeotemperature estimates from the last 14,000 (radiocarbon) years BP from D/H isotopes in peat in southern South America
Publication Date: 1999-01-01
Type: Journal Article
An automated system for hydrogen isotope analysis of water
Publication Date: 1998-11-16
Type: Journal Article
Synchronous climate changes in Antarctica and the North Atlantic
Publication Date: 1998-10-02
Type: Journal Article
Determination of the isotopic (C-13/C-12) discrimination by terrestrial biology from a global network of observations
Publication Date: 1998-09-01
Type: Journal Article
Timing is everything in a game of two hemispheres
Publication Date: 1998-08-20
Type: Journal Article
The global carbon cycle - In balance, with a little help from the plants
Publication Date: 1998-07-10
Type: Journal Article
Deuterium excess record from central Greenland
Type: Chapter
Changes in climate, ocean and ice-sheet conditions in the Ross embayment, Antarctica at 6 ka
Publication Date: 1998-01-01
Type: Journal Article
Temperature history and accumulation timing for the snowpack at GISP2, central Greenland
Publication Date: 1998-01-01
Type: Journal Article
Stable isotope records from Greenland deep ice cores: the climate signal and the role of diffusion
Type: Chapter
Changes in climate, ocean and ice-sheet conditions in the Ross embayment, Antarctica, at 6 ka
Publication Date: 1998-01-01
Type: Journal Article
Pages
Teaching
My teaching interests at the undergraduate level focus on human interactions with the environment, as well as general geosciences. I have a strong commitment to undergraduate education in this area, as I believe that an educated citizenry is important in ensuring that reasonable environmental policy is made and implemented. I teach and helped to develop a large lecture class, Introduction to Environmental Studies (ENVS 1000). This course covers the broad spectrum of environmental studies, from the social to the natural sciences. In addition, I developed and teach a large upper level undergraduate course, GEOL 3520, Environmental Issues. This course addresses our present and future energy sources, and how those energy sources affect the Earth’s systems, including climate and biogeochemistry. At the graduate level, I teach courses in my research specialty, stable isotope geochemistry and biogeochemistry. I have also taught the ENVS Honor’s course, and supervised the ENVS Internship Program. I have also been relatively successful in securing funding for education at CU. With a number of other faculty at CU, I have had grants funded by NASA (Earth System Science Education), as well as a multi-million dollar NSF-IGERT graduate training grant. This grant supported 13 graduate students per year for five years in an experiment in team building, disciplinary silo breaking, and co-educating social science, natural science, and journalism graduate students in carbon cycle dynamics, economics and policy.
Past Courses
- ENVS 1000: Introduction to Environmental Studies
- ENVS 3930: Internship in Environmental Studies
- ENVS 4990: Senior Thesis in Environmental Studies
- ENVS 5900: Carbon, Climate, and Society
- ENVS/GEOL 3520: Environmental Issues in Geosciences
- GEOL 1070: Global Change
- GEOL 1110: Global Change Lab
- GEOL 5700: Environmental Isotopes
- GEOL 5700: Current Literature in Global Change Research
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Outreach
Videos about climate change
- Abrupt Impacts of Climate Change: Anticipating surprises
- 120 Seconds of Science with Doc Ryan
- Climate Change Impacts are Happening Faster and Faster