Research Topic Summaries

The Challenge of Climate Change

The climate challenge threads through every aspect of our lives, from energy policy to changing precipitation patterns, from the spread of disease vectors to higher sea level, from shifts in ecosystem structure to diminished snowpack.

Addressing the challenge requires basic and applied research to:

  • Quantify the sinks and sources of atmospheric carbon (carbon dioxide and methane are important greenhouse gases).
  • Improve our understanding of climate processes.
  • Identify the intensity, duration, location and timing of anticipated impacts.
  • Evaluate strategies to mitigate climate change by reducing atmospheric concentrations of greenhouse gases.
  • Understand the factors that determine how humans make decisions about the environment.
  • Develop and analyze policy instruments and options.

Check out the links below for highlights of research being conducted at Columbia in these areas. We will update these pages with new research results periodically. Also see our Climate Matters Blog and News & Events for exciting new research.

Research Topics

Quantifying the Oceanic Sink of Carbon Dioxide:

What is the role of the ocean in regulating atmospheric carbon?

The radiative balance (i.e. heat balance) of our planet depends on the atmospheric concentration of greenhouse gases (GHGs), especially carbon dioxide. As we drive our cars and heat and cool our homes, carbon dioxide is emitted into the atmosphere. Increasing levels of greenhouse gases result in higher temperatures and a changing climate. About half of the anthropogenic CO2 that is emitted due to human activities remains in the atmosphere, while the rest is taken up by the ocean and by land plants.

Under the Kyoto Protocol it will be necessary to monitor the fate of atmospheric carbon dioxide. A key component to this monitoring is to quantify the patterns of exchange of carbon dioxide between the land, ocean and atmosphere. Taro Takahashi of the Lamont-Doherty Earth Observatory has made significant contributions to our understanding of the distribution of oceanic carbon and the exchange of carbon dioxide between the ocean and the atmosphere.

How do we estimate the exchange between the ocean and the atmosphere?

The exchange, or flux, of CO2 between the ocean and the atmosphere depends on the difference between the partial pressure of carbon dioxide in the ocean and the atmosphere and an exchange factor. The exchange factor is usually estimated from wind speed because it is easy to measure and we have global maps of wind. By contrast, it is difficult to measure the difference between the partial pressure in the atmosphere and ocean, so such observations are relatively scarce, especially in remote locations. Taro Takahashi has compiled 940,000 measurements of the difference in the air-sea partial pressure of CO2 made between 1958 and 2000.

What do the patterns of air-sea exchange look like?

The global net uptake of the ocean is 2.3 x 1015 grams of carbon a year for the reference year of 1995. (Since carbon dioxide has increased steadily in the ocean due to increases in the atmosphere as a result of anthropogenic emissions, all measurements are corrected to the reference year of 1995). Regions that absorb atmospheric carbon are known as sinks, and regions that release it to the atmosphere are known as sources. The equatorial Pacific and Arabian Sea are the strongest source areas (Figure), as deep carbon-rich water rises to the surface due to upwelling. The regions between 40 and 60o latitude in both hemispheres are strong sink areas. In these areas, the cooling of warm waters as they travel north and the active growth of microscopic plants combine with high wind speeds to produce large fluxes of CO2 into the ocean. During El Nino the equatorial Pacific is a much weaker source because upwelling is reduced, so El Nino years have not been included to obtain this global estimate.

Does the increasing concentration of carbon dioxide in the surface ocean mirror the atmospheric increase?

In the north and equatorial Pacific there are enough measurements to allow us to quantify changes over time.

  • The average partial pressure of CO2 in the open ocean increased in the north Pacific between 1970 and 2004 at about the same rate as it did in the atmosphere. However, oceanic partial pressure of carbon dioxide decreased near the southern Bering Sea and the Okhotsk Sea. Takahashi and colleagues believe this is because of increased photosynthesis and changes in the rates of lateral and vertical mixing over the study period.
  • In the equatorial Pacific, the partial pressure of carbon dioxide in the surface ocean from 1981 and 2004 has increased on average the same as it has in the atmosphere. However, the partial pressure of CO2 decreased or remained constant before 1990, while after 1990 it increased as fast or faster than CO2 increased in the atmosphere. This change is likely due to oceanographic conditions such as the rate of upwelling or lateral transport.

Where can I get the data?

Takahashi has made his updated database of carbon dioxide available to the public.  It includes more than three million quality-controlled measurements made from 1986 to 2006 throughout the global ocean, from both open ocean and coastal locations.


Takahashi, T.,  S.C. Sutherland, C. Sweeney, A. Poisson, N. Metzl, B. Tilbrook, N. Bates, R. Wanninkhof, R. A. Feely, C. Sabine, J. Olafsson and Y. Nojiri. 2002. Global sea–air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects. Deep Sea Research Part II, 49 ( 9-1) 1601-1622. [download]

Feely, R. A., T. Takahashi, R. Wanninkhof, M. J. McPhaden, C. E. Cosca, S. C. Sutherland, and M.-E. Carr. 2006. Decadal variability of the air-sea CO2 fluxes in the equatorial Pacific Ocean. Journal of Geophysical Research, doi: 10.1029/2005JC003129. [download]

Takahashi, T, S.C. Sutherland, R.A. Feely and R. Wanninkhof. 2006. Decadal change of the surface water pCO2 in the North Pacific: A synthesis of 35 years of observations. Journal of Geophysical Research, 111 (C7), doi:10.1029/2005JC003074. [download]

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North American Drought Atlas

Will climate change bring more droughts?

It is expected that increased greenhouse gas concentrations will modify the patterns of rainfall throughout the world, with decreased total precipitation in the subtropics (between 20 and 35o latitude in both hemispheres) and to the north of the subtropics. Regions such as the Mediterranean, northern Africa and the Middle East, southwestern North America and Southeast Asia will likely experience more frequent and longer droughts, with less frequent but more intense rain events. When confronted with droughts such as that observed in summer of 2002 in the central and western U.S. and or the one experienced from 2007 to 2008 in the southeastern U.S., much can be learned from the historical record.

What are tree rings and what do they tell us?

Each year, as trees or woody shrubs grow, they produce wood cells that form a ring around the circumference of the trunk. The width of a tree ring and other factors (like the density of the cells) reflect environmental conditions (such as moisture and temperature) experienced during the growing season. Information on annual tree rings is compiled into chronologies of standardized growth rates for each year. These chronologies provide a record of environmental conditions observed at that location; when combined together, they tell us about past climate.

Researchers from the Tree-Ring Lab at the Lamont-Doherty Earth Observatory use tree-ring chronologies from Asia, the Americas and Siberia to improve our understanding of past environmental conditions. These chronologies provide information about regional weather patterns, teleconnections between climate conditions at distant locations, and human impacts on forest growth.

What is the North American Drought Atlas?

The North American Drought Atlas is a collection of 835 annual tree-ring chronologies from across North America. Most of the chronologies begin before 1700, all extend to at least 1979, and many of them are 400 to 1000 years long.  Each location in the atlas has a temporal record of an index that provides a measure of the conditions of raininess or drought. The index, known as the Palmer Drought Severity Index or PDSI, is standardized to reflect local climate.

What do we learn from the history of droughts?

The Drought Atlas provides information about the extent and intensity of drought conditions in the past. Although 80 percent of the contiguous United States was under conditions of moderate to severe drought in 1934 during the Dust Bowl, twentieth century droughts pale in comparison to the “mega drought” of the 16th century. It started in Mexico before spreading northwest and east. The mega drought coincides with historical accounts of increased conflict, such as the Chichimeca War in Zacateca (Mexico) in 1550, and with non-conflict related social collapses, such as the abandonment of pueblos in New Mexico. On the east coast, a colony on Roanoke Island mysteriously disappeared shortly after being established in 1587 and settlers at Jamestown reported “an appalling death rate” between 1609 and 1610.

This image from the Library of Congress, Prints & Photographs Division, FSA/OWI Collection, LC-USF34-004073-E, taken by Arthur Rothstein for the Farm Security Administration, shows an orchard covered by dust in Cimarron County (Oklahoma) during the Dust Bowl.

What additional resources help us understand droughts?

Drought conditions worldwide appear to be related to ocean temperatures in the equatorial Pacific. Numerical modeling of ocean conditions and climate can be supported by extending tree-ring chronologies further back in time with chronologies from corals and sediments from the equatorial region.


Cook, E.R., C.A. Woodhouse, C.M. Eakin, D.M. Meko and D.W. Stahle, 2004. Long-term aridity changes in the western United States. Science. 306(5698): 1015-1018.

Cook, E.R., R. Seager, M.A. Cane and D.W. Stahle, 2007. North American Drought: Reconstructions, Causes, and Consequences. Earth Science Reviews. 81, 93-134.

Seager, R., N. Graham, C. Herweijer, A.L. Gordon, Y. Kushnir and E. Cook, 2007. Blueprints for Medieval hydroclimate. Quaternary Science Review. doi:10.1016/j.quascirev.2007.04.020.

Stahle, D.W., E.R. Cook, M.K. Cleaveland, M.D. Therrell, D.M. Meko, H.D. Grissino-Mayer, E. Watson, and B.H., Luckman, 2000. Tree-ring data document 16th century megadrought over North America, Eos, Transactions of the American Geophysical Union 81(12): 212, 125. Reprinted by AGU in Earth in Space, March 2000.

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Climate Change and Public Health

How does climate affect health?

Climate has a direct impact on public health. Increased temperatures led to more than 20,000 deaths during the European heat wave in summer of 2003. As is true for most aspects of climate change, developing nations and the poor within developed nations will be disproportionately impacted by future public health impacts.

Rising temperatures and changes in patterns of rainfall are expected to result in:

  • Changes in the geographic distribution and transmission season for malaria.
  • Increased diarrheal disease.
  • Changes in the geographic and seasonal patterns of vectors of infectious disease.
  • Increased heat-related mortality.
  • Increased cardio respiratory diseases due to decreased air quality.

Can we predict future impacts?

Predicting the future health impacts of climate change is complex, as the impacts depend on many factors, such as the degree to which people and ecosystems will adapt. For example, changes in use of air-conditioning affect the likelihood of mortality associated with extreme heat events.

Likewise, changes in population and population density must also be taken into account. Projections of the future spread of malaria have stronger dependence on estimates of future population than on the different climate models.

The world is becoming more urban (by 2030, 60 percent of global population will be urban dwellers). This introduces additional elements for public health. Although increased urbanization often improves access to safe water and healthcare, rapid economic growth and unplanned urbanization can increase the disease burden of malaria or dengue in places like India and Africa. Cities increase local temperature, in what is known as the heat island effect, and they modify precipitation patterns.

How will cities be affected?

Studies carried out at the Mailman School of Public Health show that heat-related mortality in New York City may double by 2050; the impact will be largest in city outskirts and for the poor living in multi-family dwellings without air-conditioning. Air quality in tomorrow’s cities is likely to be much worse. Days in which ozone levels will exceed maximum safety levels will be 68 percent more frequent in 2050 compared to 1990 for fifty cities in the northeastern U.S., leading to up to a five percent increase in asthma for people over 65.

How will vectors of infectious disease be affected?

As rainfall patterns change and temperature increases, conditions that support vectors of infectious disease will shift in space, potentially spreading into regions where human populations have low, or no, immunity. In urban centers of developing nations, high population density and poor sanitation practices can accelerate infection rates.

As temperatures increase, tropical disease vectors will likely extend to temperate regions as well. An outbreak of chinkungunya in Italy in 2007 was brought about by the entry of tiger mosquitoes (shown in this picture from the Centers for Disease Control), which are originally from Southeast Asia and are also potential carriers of dengue fever.

Can we predict the risk of disease?

Researchers at the International Research Institute for Climate and Society (IRI) have developed systems based on environmental indicators to predict the risk of diseases such as malaria (Malaria Early Warning System), meningitis and Loa loa.

The ability to predict likelihood of disease requires several steps.

  • Identify environmental conditions that are associated with the disease and can be measured or modeled (e.g. rainfall, temperature, dust and vegetation).
  • Design models that relate the likelihood of disease occurrence with the predictor environmental variables.
  • Generate maps of the likelihood of disease incidence based on the predictor environmental factors (observed or modeled).
  • Demonstrate the utility of this framework for decision makers.

Research into the environmental links to patterns of malaria had been underway for thirty years before the use of environmental predictors became routine, so the last step represents a significant challenge.


Cuevas, L.E., I. Jeanne, A. Molesworth, M. Bell, E.C. Savory, S.J. Connor and M.C. Thomson. 2007. Risk mapping and early warning systems for the control of meningitis in Africa. Vaccine 25, Supplement 1, A12-A17. [download]

Knowlton, K., B. Lynn, R.A. Goldberg, C. Rosenzweig, C. Hogrefe, J.K. Rosenthal and P.L. Kinney. 2007. Projecting heat-related mortality impacts under a changing climate in the New York City region. 2007. American Journal of Public Health. 97 (11), 2028-2034. doi: 10.2105/AJPH.2006.102947. [download]

Worrall, E., S.J. Connor and M. C. Thomson. 2007. A model to simulate the impact of timing, coverage and transmission intensity on the effectiveness of indoor residual spraying (IRS) for malaria control. Tropical Medicine and International Health. 12 (1), 75–88,  doi:10.1111/j.1365-3156.2006.01772. [download]

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The Carb-Fix Experiment

What is the advantage of mineral sequestration?

Mitigation of climate change involves the reduction of the emissions of greenhouse gases, primarily carbon dioxide. If CO2 is captured at point sources, such as power plants, that have large emissions, the challenge becomes finding a way in which to store the captured carbon dioxide. One strategy is to store it in geographic formations or in the deep ocean.

Another approach is mineral sequestration into basalts. Rocks containing magnesium or calcium silicate, such as basalt, are converted into carbonates of calcium, magnesium and iron in the presence of dissolved carbon dioxide. Mineral sequestration is a permanent and secure way to store carbon dioxide.

The Carb-Fix Experiment,

a collaboration between Reykjavik Energy, France CNRS, the University of Iceland and Columbia University, aims to demonstrate the feasibility of the mineral sequestration of carbon dioxide into basalts. This project represents a proof of concept. Extensive basalt shields worldwide hold the potential for stable mineral storage for thousands or millions of years, which might make “near zero emission”geothermal power plants a possibility.

An ideal study site:

The study site is the Hellisheidi Geothermal Plant in Iceland, where conditions are ideal for such a pilot project.

  • There is abundant fresh water and CO2 gas.
  • Dissolvable basalts make up 90 percent of the bedrock.
  • The exceptional infrastructure at the Hellisheidi plant and the on-site team of scientists, engineers and craftsmen contribute considerably to success of the project.

The process:

CO2 is taken from the geothermal wells, dissolved in fresh water and injected into the ground to depths from 400 to 800 meters. As the water travels horizontally along the depth of injection, basalt reacts naturally with the carbon dioxide, capturing it into carbonates. An initial tracer test in 2007/2008 evaluated the groundwater system, including patterns and rates of flow, and ensured that the site will not leak. Monitoring during the main project will be done via five wells at 60 meters, 1500 meters and 2700 meters downstream from the injection well and in the soil around the injection site and wells.

The need for regulatory frameworks:

Carbon capture and sequestration on a larger scale will require the development of various regulatory frameworks. Laws and regulations will be needed regarding the environmental impacts both at the surface (to avoid disturbing pristine areas) and subsurface (to prevent groundwater contamination). The potential for leakage of CO2 to the atmosphere must be carefully monitored, thus ongoing monitoring and verification of the site are an integral part of the project and will be part of any demonstration or pilot study.

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Decision Science

Do scientists communicate climate information effectively?

Communicating the risks and opportunities associated with climate change is a key challenge for climate scientists. Studies at the Center of Research on Environmental Decisions suggest that current modes of communication may not be appropriate.

Most climate forecasts are presented as numerical probabilities, based on the assumption that people process information analytically. However, research suggests that people receiving this type of information either tend to fail to act or they over-react.

How do people process information?

Humans reflect on current conditions using two different systems:

  • In experiential processing, people relate current situations to past experiences.
  • In analytical processing, people relate the current situation to the sum of all past experience.

Dust Bowl

Though thinking involves both kinds of processing, the emotional impact of personal experience tends to overwhelm abstract information. If extreme events are communicated on personal terms, they can become part of the emotional makeup of individuals or groups who were not involved themselves. Images such as this one of hitchhikers on their way to California in 1937, have made the Dust Bowl a reality for many Americans born after the 1940s (Library of Congress, Prints & Photographs Division, FSA/OWI Collection LC-DIG-ppmsc-00235, taken by Dorothea Lange for the Farm Security Administration).

For both individuals and groups making decisions, experience has greater impact than scientific description. Numerical information is generally interpreted through the lens of personal experience, including how recently a relevant experience occurred and the emotional charge associated with it.

What other factors play a role in how we respond to climate information?

There are two additional factors that can contribute to inadequate responses to climate information:

  • Individuals tend to have a finite pool of worry, which means that feeling concern for a stressful condition tends to reduce concern for other conditions.
  • People tend to explore a single solution and then stop, a tendency known as the single action bias.

How can we use these findings to communicate better?

Relating numerical information to conditions in recent memory or translating it into concrete images, strong emotions or stories enables an individual or group to understand the abstract information as an experience. Group discussions can have the same effect when experiences are shared among group members. These approaches not only help increase the intuitive understanding of abstract information, but they have the added benefit of leading to a larger number of proposed solutions.


Marx, S., E.U. Weber, B.S. Orlove, A. Leiserowitz, D.H. Krantz, C. Roncoli and J. Phillips. 2007. Communication and Mental Processes: Experiential and Analytic Processing of Uncertain Climate Information. Global Environmental Change 17(1), 47-58.[download]

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The Path to Climate Sustainability, a joint statement made by the Global Roundtable on Climate Change, based at the Earth Institute at Columbia University, describes a pathway for climate change policy. This statement was released on February 20, 2007, and has been endorsed by 108 companies and institutions from around the world and 138 individuals from business, civil society, governments and research institutions. It highlights the urgency for global action to reduce emissions of carbon dioxide.

While acknowledging the importance of increased energy efficiency, the signatories also recognize the need to use non-fossil-fuel energy sources and to deploy technologies to capture and store carbon dioxide. The statement emphasizes that success is possible and indicates how success may be reached. The signatories call for concerted action of governments, the private sector, trade unions and other sectors of civil society. There is a strong emphasis on the global scope of the problem, such that all countries must be party to the accord, with commitments to action reflecting their level of economic development.

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