Theme II research objectives involve the development, collection, analysis, and archiving of instrumental and paleoclimate data. Based on these observations, scientists expect to better understand the Earth’s climate history, sensitivity to changes in internal and external forcings and processes, and to develop scenarios that can be tested using climate models. The goals include efforts to refine model predictive skills of important climate phenomena through model data comparisons and to improve the documentation of the state of the oceans. Research under this theme is therefore closely connected with research under Theme I: Earth System Modeling. An example of one such link is the multidisciplinary LDEO project ARCHES (AbRupt Climate ChangE Studies) in which LDEO scientists engage in research to understand the phenomenon of abrupt climate change and assess the possibility of such changes in the future.

Modern Observations: The Lamont-Doherty Earth Observatory (LDEO) and Ocean and Climate Physics (OCP) scientists use existing observations and plan and execute new observations to advance the knowledge of the state of the ocean and monitor its variability. These data are used to assess the mass, heat, and fresh water transport through the ocean circulation system and provide benchmarks for model evaluation. Modern observational data contributes to the formulation of model parameterizations that help address model sub-grid-space processes. In this context, LDEO OCP research is pursuing the collection and interpretation of modern hydrographic and tracer observations in ocean areas such as the Southern Ocean, the North Atlantic, and the boundary between the Indian and Pacific Oceans (Indonesian Throughflow region). LDEO ocean research has a long history of pursuing an approach that is well balanced between observations and modeling.


Modern observations at LDEO are not limited exclusively to hydrographic observations. Within the Geochemistry Division (GD) extensive tracer work is carried out to address issues related to the physical climate system and the environment. Using in-situ observations and remote sensing from space, scientists are observing and studying the uptake of carbon dioxide by the world ocean, a crucial issue in the study of the global carbon cycle, and possible future anthropogenic forcing of climate change. This work has been going on for several decades and involves collaboration with many other national institutions including NOAA laboratories (AOML and PMEL). Another key area where tracer observations are being studied at LDEO is the formation and circulation of Atlantic deep-water masses. Elements of this work are performed in collaboration with the NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML).

Paleoclimate Observations: In the field of paleoclimate observations, LDEO scientists study the climate history of the Earth over a broad range of time scales and epochs. The LDEO involvement in this area of research is extremely diverse. The study of the pre-instrumental history of the Earth’s climate is critical for evaluating our ability to understand the modern climate system response to a variety of forcing scenarios and internal dynamical mechanisms. It is also a test of our ability to simulate the climate system under different external radiative forcing and the development of reliable climate models. Under CICAR, special efforts are made to emphasize a robust collaboration between the strong numerical modeling elements of GFDL and LDEO and the expertise in proxy data collection and analysis at LDEO.

The collection, archiving, and analysis of paleoclimate data at LDEO are carried out in two of the Observatory divisions: the Geochemistry Division (GD) and the Biology and Paleo Environment (B&PE) Division. Scientists use geochemical measurements of deep-sea sediments to study the geological history of the ocean circulation, particularly fluctuations in the strength of the global thermohaline circulation. Much of this work is done by studying sediment cores (stored at the LDEO Core Laboratory) in key ocean areas such as the Cape Basin in the South Atlantic, the tropical regions, and the polar oceans. Particular emphasis is placed on understanding the ocean and climate signature of the last deglaciation and climate instabilities during subsequent millennia of the current, warm, Holocene period. Lamont scientists are very active in developing paleoclimate records that document amplitudes and timing of abrupt climate changes in the recent geological past. These records provide the most compelling evidence of how dramatically Earth’s climate can respond to modest changes in climate forcing. Some of these climate shifts have been linked to junctures in early human evolution and collapses of ancient urban civilizations. Additionally, Lamont scientists are developing new paleo proxies of ocean and climate processes and examining new geographical locations in order to add new information to the emerging discoveries in this area.


In the B&PE Division paleoclimate observationalists emphasize, but do not limit themselves to, the use of biological indicators to study the Earth’s climate history. Here too, scientists study deep-sea sediments to uncover climate variations on paleo time scales while others use trees, corals, pollen stored in lake sediments, and sea shells to reconstruct the past. Some of the records studied here have excellent temporal resolution, thus allowing a closer look at the history of phenomena such as El Niño or decadal climate variation, which can be found in the North Atlantic and North Pacific (NAO and PDO, respectively). Key projects are the uncovering of the recent history of centennial timescale variability in the North Atlantic and linking it to variations in solar irradiance during the Holocene.


Tree rings are studied intensively at the Lamont Tree Ring Laboratory (TRL) to provide a high-resolution climate history of the last few millennia. The climate information in long annual tree-ring records helps put climate variations and trend found in short instrumental records in a broader temporal perspective, especially related to the temperature variability over the past millennium. Long tree-ring records have been used to develop the first strongly verified multi-proxy reconstruction of the NAO covering the past 600 years and of long-term ENSO decadal variability. Reconstructions of past hydro-climatic variability in North America add important contributions on local to continental scales as well.