Articles by Jeffrey Sachs

Topic: Climate

<< View all writings by year
<< Return to Bio page


Smaller than a speck of dust, Emiliania huxleyi plays an outsized role in the world's seas. Ranging from the polar oceans to the tropics, these free-floating photosynthetic algae remove carbon dioxide from the air, help supply the oxygen that we breathe, and form the base of marine food chains. When they proliferate, their massive turquoise blooms are visible from space.

The building and burial of E. huxleyi's coccoliths makes it an important player in the global carbon cycle. (Dee Breger/Micrographic Arts)

Now scientists have discovered one of the keys to E. huxleyi's success. A seven-year effort by 75 researchers from 12 countries to map its genome has revealed a set of core genes that mix and match with a set of variable genes that likely allows E. huxleyi, or Ehux, to adapt to different environments. Their results are described in the latest issue of Nature.

Over generations, the exchange of material within Ehux's so-called "pan-genome" has allowed it to evolve in far-flung places. "In the sea, we thought that only bacteria were shuffling around their genes in this way, so it was a real shock to see that Ehux was doing the same thing," said senior co-author of the study Sonya Dyhrman, a microbial oceanographer at Columbia University's Lamont-Doherty Earth Observatory.

Like all phytoplankton, Ehux harvests sunlight from the upper layer of the world's oceans. But it sets itself apart by building armor-like plates of chalk, or coccoliths. It lives mostly in cold, nutrient-rich waters but also thrives at the warm, nutrient-poor equator. Its variety of shapes and sizes, and the diverse places it calls home, hint at its extreme versatility.

Two-thirds of Ehux's genes are shared among all strains. This core genome allows Ehux to thrive under low levels of phosphorus and iron, elements key to life but in short supply in the ocean. The remaining third of its genes are present in one but not all strains. In this variable gene pool are those that allow Ehux to use varying forms of nitrogen, another relatively scarce element in the sea. This flexibility likely allows it to adapt to changing environmental conditions. 

A pan-genome has previously been seen only in some marine bacteria, organisms lacking enclosed nuclei. Ehux is a eukaryote—an organism with an enclosed nucleus, like all plants and animals. This is the first description of a pan-genome in eukaryotic marine algae.

"We're starting to get a window into the variations that allow the oceans to function the way they do," said Tatiana Rynearson, an oceanographer at University of Rhode Island who was not involved in the study.  "Will this pan genome trend hold for other microalgae in the ocean?"

Emiliania huxleyi's shapes are as varied as the ocean environments it lives in. (Nature)

Understanding what makes Ehuxso easygoing may help scientists understand how rising industrial carbon emissions will affect climate and ocean health in the future. Industrial carbon is warming Earth's atmosphere but also acidifying its oceans. Coccolithophores play an important role in removing carbon from both places.

They combine it with calcium to build their coccoliths—for each ton, removing 320 pounds of carbon. They also convert it into biomass during photosynthesis, producing oxygen as a byproduct. What's more, their blooms release dimethyl sulfide into the air, creating clouds, which reflect sunlight into space and cool the planet.

Depending on where they are and what they're doing, coccolithophores can also release carbon dioxide, making it difficult for scientists to say for sure whether they take up or release more carbon over time. This question becomes important as increasing levels of carbon in the atmosphere change the ocean's chemistry. As seawater acidifies, the form of carbon that Ehux and other calcifying organisms need to build their coccoliths become scarcer. If seawater grows acidic enough, it could dissolve them entirely.

Coccolithophore bloom off Brittany, France (Jacques Descloitres, NASA)

Ehux may adapt, and even grow better under more acidic conditions, but its contribution to the carbon cycle could change dramatically. The genome allows researchers to study how the pan-genome is expressed, and potentially predict Ehux's response. "Where will it be?" said Dyhrman. "What will it be doing? These seem like simple questions, but they could have a big impact on the net result of how carbon in the ocean is cycled."

On the eukaryotic tree of life, Ehux belongs to the haptophytes, which are important for understanding how eukaryotes, and especially land plants, evolved. The genome brings scientists closer to understanding the evolution of life on Earth as well as how organisms evolve to exploit diverse environments. "It gives you the code to decipher the signals you see in the sea," said Dyhrman.

The Ehux genome revealed other surprises that could lead to practical benefits. Some of its metabolites, known as polyketides, have anti-microbial, anti-fungal, anti-parasitic and anti-tumor properties that could be used to treat disease. Identifying the genes and proteins used in the coccolith-building process could also lead to the design of new materials for bone replacement, sensing systems and optoelectronic devices.

"Sustainable Visions," Project Syndicate, June 7, 2013.

"Paths to Sustainable Power," Project Syndicate, March 28, 2013.

"A Better Way to Fight Climate Change," Project Syndicate, February 28, 2013. Download as [PDF]

"America’s New Progressive Era?" Project Syndicate, January 31, 2013. Download as [PDF]

"Writing the Future," Project Syndicate, January 24, 2013. Download as [PDF]


"Obama Has Four Years to Fix the Economy," Financial Times, November 11, 2012. [Download as PDF]

"Attention, Mr. President: No Politics, Just Our Solutions — Saving the Climate," Parade, November 4, 2012. Download as [PDF]

"Green Growth and Equity in the Context of Climate Change: Some Considerations," with Shiv Someshwar. ADBI Working Paper Series 371, July 2012. Download as [PDF]

"Our Summer of Climate Truth," Project Syndicate, July 27, 2012. Download as [PDF]

"A Rio Report Card," Project Syndicate, June 18, 2012. Download as [PDF]

"From Millennium Development Goals to Sustainable Development Goals," The Lancet, June 9, 2012. Download as [PDF]

"Sustainable Humanity," Project Syndicate, January 31, 2012. [Download as PDF]


"The Murdoch Legacy," Huffington Post, October 10, 2011. [Download as PDF]

"In the Front Line," Our Planet, September 2011. [Download as PDF]


"A New Path to a Low-Carbon Economy," Project Syndicate, October 27, 2010. [Download as PDF]

"Growth in a Buddhist Economy," Project Syndicate, August 25, 2010. [Download as PDF]

"Making Sense of the Climate Impasse," Huffington Post, August 2, 2010. [Download as PDF]

"Sow the seeds of long-term growth." Financial Times, July 21, 2010. [Download as PDF]

"Fixing the Broken Government Policy Process." Scientific American. February 2010. [Download as PDF]


"Hold the rich nations to their word," Financial Times, 16 December 2009. [Download as PDF]

"End the Politics -- Let Scientists and Engineers Lead," Huffington Post, 3 December 2009. [Download as PDF]

"Enough posturing politics. Time to let the experts lead." The Guardian. 2 December 2009. [Download as PDF]

"Transgressing Planetary Boundaries," Scientific American, December 2009. [Download as PDF]

"A Clunker of a Climate Policy." Scientific American. November 2009. [Download as PDF]

"Still Needed: A Climate Plan", Scientific American, July 2009

"Still Needed: A Climate Plan." Scientific American. July 2009.

"Putting a Price on Carbon: An Emissions Cap or a Tax?" Yale Environment 360. 7 May 2009. [Download as PDF]

"3 billion poor people need world's help." 20 March 2009. [Download as PDF]

"Transforming the Auto Industry." Scientific American. February 2009. [Download as PDF]

"Eight Principles for a Global Agreement on Climate Change." COP15 UN Climate Change Change Conference Blog. 28 January 2009. [Download as PDF]


"Using Carbon Taxes to Pay for Development." Financial Times. 24 September 2008. [Download as PDF]

"Climate Change: feed it and weep, or lead and reap." Sydney Morning Herald. 25 July 2008. [Download as PDF]

"A User's Guide to the Century." The National Interest. 2 July 2008. [Download as PDF]

"Less talk, more action needed." The Guardian. 25 June 2008.

"Technological Keys to Climate Protection." Scientific American. March 2008. [Download as PDF]

"Climate Change after Bali." Scientific American. February 2008. [Download as PDF]


"Meaningful Goals for Climate Talks." Scientific American. December 2007. [Download as PDF]

"Climate Change and the Law." Scientific American. November 2007. [Download as PDF]

"Making Development Less Risky." Scientific American. August 2007. [Download as PDF]

"Climate Change Refugees." Scientific American. June 2007.
[Download as PDF]

"The Road to Clean Energy Starts Here." Scientific American. May 2007.
[Download as PDF]

"A Climate For Change." TIME Magazine. 8 March 2007.

[Download as PDF]

"Moving Beyond Kyoto." Scientifc American. February 2007.
[Download as PDF]


"Fiddling While the Planet Burns." Scientific American. October 2006.
[Download article as PDF]

"Ecology and Political Upheaval." Scientific American. July 2006.
[Download article as PDF]

"Pay for it Now, or Pay for it Later." The Globe and Mail. 19 June 2006.
[Download article as PDF]

"Investments Toward Sustainable Development," with Walter V. Reid. Science, Vol. 312. 19 May 2006.
[Download article as PDF]


"A Robust Strategy for Sustainable Energy," with Klaus Lackner. Brookings Papers on Economic Activity, Issue 2. 2005.
[Download article as PDF]

The End of Poverty: Economic Possibilities for Our Time, The Penguin Press: New York, 2005.

Investing in Development: A Practical Plan to Achieve the Millennium Development Goals, UN Millennium Project, (Director),  Earthscan: New York, 2005.


“We Can End World Hunger: Here’s How,” with Pedro Sanchez, World Ark, November/ December 2004.
[Download article in PDF format]

"Seeking a Global Solution: The Copenhagen Consensus neglects the need to tackle climate change," Nature, August 12, 2004.
[Download article in PDF format]

"Sustainable Development," Science, April 30 2004.
[Download article in PDF format]


"Getting Through the Bottleneck," Our Planet: The Magazine of the UNEP, Vol. 13 No 4. (2003 Issue: Globalization, Poverty, Trade, and the Environment)  [Download as PDF]


"Compensation for 'Meaningful Participation' in Climate Change Control: A Modest Proposal and Empirical Analysis" with T. Panayotou and A. Peterson Zwane, Journal of Environmental Economics and Management,  43, pp. 437-454, 2002.
[Download paper as PDF]


"Reducing the Vulnerability to Natural Disasters: Hurricane Mitch and Central America," with Juan Carlos Barahona, Eduardo Doryan and Felipe B. Larrain Economic Development in Central America, Vol. II: Structural Reform edited by Felipe B. Larrain.  Harvard University Press, 2001.
[Download paper in PDF]

"The Geography of Poverty and Wealth," with Andrew D. Mellinger and John L. Gallup. Scientific American. March 2001.
[Download article as PDF]


"Climate, Coastal Proximity, and Development," with Andrew Mellinger and John Gallup in Oxford Handbook of Economic Geography, edited by Gordon L. Clark, Maryann P. Feldman, and Meric S. Gertler, Oxford University Press, 2000.
[Download paper as PDF file]
(Previously "Climate, Water Navigability, and Economic Development," with Andrew Mellinger and John Gallup, CID Working Paper No. 24, September 1999. [PDF])

"Agriculture, Climate, and Technology: Why are the Tropics Falling Behind?" with John Luke Gallup, American Journal of Agricultural Economics.  Vol. 82, pp. 731-777, August 2000.
[Download paper as PDF]


"Developing Countries and the Control of Climate Change: A Theoretical Perspective and Policy Implications," with Theodore Panayotou and Alix Peterson. HIID CAER II Discussion Paper No. 44, November 1999. [Download as PDF]

"Developing Countries and the Control of Climate Change: Empirical Evidence" with Theo Panayotou and Alix Peterson, CAER II Discussion Paper No. 45, August 1999. CC [Download paper as PDF]

"Developing Countries and the Control of Climate Change: A Theoretical Perspective and Policy Implications," with Theo Panayotou and Alix Peterson, prepared for UNAID/CAER II, CAER II Discussion Paper No. 44, August 1999. [Download paper as PDF]


"The New Geopolitics." Scientific American. June 2006.
[Download article as PDF]

"It's too late to seal a global climate deal. But we need action, not Kyoto II." The Guardian. 30 September 2009.