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James Hansen

James Hansen

BornMarch 29 1941
Denison, Iowa
EducationPhysics, University of Iowa
OccupationHead of NASA Goddard Institute for Space Studies

James E. Hansen (born March 29 1941 in Denison, Iowa) heads the NASA Goddard Institute for Space Studies[1] in New York City, a part of the Goddard Space Flight Center in Greenbelt, Maryland, Earth Sciences Division.[2] He is also currently an adjunct professor in the Department of Earth and Environmental Sciences at Columbia University. Hansen is best known for his research in the field of climatology and his testimony on climate change to congressional committees in the 1980s that helped raise broad awareness of the global warming issue. He is also noted for publishing "an alternative scenario" for global warming which states that in the past few decades the warming effect produced by increased CO2 has been largely offset by the cooling effect of aerosols also produced in burning fossil fuels, and that most of the net warming so far is due to trace greenhouse gases other than CO2.[3] He has been a critic of both the Clinton and current Bush Administration's stances on climate change.[4]



Hansen was trained in physics and astronomy in the space science program of Dr. James Van Allen at the University of Iowa. He obtained a B.A. in Physics and Mathematics with highest distinction in 1963, an M.S. in Astronomy in 1965 and a Ph.D. in Physics, in 1967, all three degrees from the University of Iowa. He participated in the NASA graduate traineeship from 1962 to 1966 and, at the same time, between 1965 and 1966, he was a visiting student at the Institute of Astrophysics at the University of Kyoto and in the Department of Astronomy at the University of Tokyo.

Honors and awards

Hansen was elected to the National Academy of Sciences in 1996[5] and he received the Heinz Environment Award[6] for his research on global warming in 2001. He was listed as one of Time Magazine's 100 Most Influential People in the Time 100 (2006) list and, in 2007, he was awarded the Dan David Prize.

Field of research and interests

As a college student in the University of Iowa, Hansen was attracted to science and research by James Van Allen's space science program in the physics and astronomy department. A decade later, he started focusing on planetary research that involved trying to understand the climate change on earth that will result from anthropogenic changes of the atmospheric composition.

One of Hansen’s research interests is radiative transfer in planetary atmospheres, especially interpreting remote sounding of the earth's atmosphere and surface from satellites. Such data, appropriately analyzed, may be one of the most effective ways to monitor and study global change on the earth.

Hansen is also interested in the development and application of global numerical models for the purpose of understanding current climate trends and projecting humans' potential impacts on climate.


Hansen has made a number of statements concerning global warming. Among these are:

  • Warming in recent decades has been driven mainly by non-CO2 greenhouse gases (GHGs), such as chlorofluorocarbons, CH4, and N2O, not by the products of fossil fuel burning, CO2 and aerosols, the positive and negative climate forcings of which are partially offsetting. [...] This does not alter the desirability of limiting CO2 emissions, because the future balance of forcings is likely to shift toward dominance of CO2 over aerosols [7]
  • A global tipping point will be reached in 10 years (starting from 2006) if levels of greenhouse gases such as methane and CO2 are not reduced. Global warming at this point becomes unstoppable.[8]
  • Global warming was 0.5–0.75 °C in the past century, and about 0.3 °C in the last 25 years
  • Climate sensitivity to CO2 doubling is 3±1 °C.
  • The dangerous concentration of CO2 can be no more than approximately 450 ppm. However, he now believes that it is "probable that the dangerous level is even lower."[9]
  • A feasible strategy for planetary rescue almost surely requires a means of extracting greenhouse gases from the air.[9]
  • When asked about "science skeptics", he replied that he "actually don't like the word "skeptics" for them; I think it's better to call them "contrarians," because all scientists are skeptics. If you're not skeptical as a scientist, you're not going to be very successful. You have to continually ask yourself how well your theories agree with the real world, and you can't fudge that." [1]


In 1981 Hansen and a team of scientists at Goddard had reached the conclusion that carbon dioxide in the atmosphere would lead to global warming sooner than previously predicted. While other climatoligists had already predicted that a trend would be apparent by 2020, Hansen predicted, in a paper published in Science, that the change was already occurring and that there would record high temperatures as early as 1990. He also predicted that it would be difficult to convince politicians and the public to react.[10]

In 2000 he authored a paper called Global warming in the twenty-first century: an alternative scenario[11] in which he presents a more optimistic way of dealing with global warming focusing on non-CO2 gases and black carbon in the short run, giving more time to make reductions in fossil fuel emissions. He notes that warming observed to date is largely due to non-CO2 gases. This is because CO2 warming is offset by climate-cooling aerosols emitted with fossil fuel burning and because non-CO2 gases, taken together, are responsible for roughly 50% of greenhouse gas warming.


In 2003 Hansen wrote a paper called Can We Defuse the Global Warming Time Bomb [12]. In it, he argues that human-caused forces on the climate are now greater than natural ones, and that this, over a long time period, can cause large climate changes. He further states that a lower limit on “dangerous anthropogenic interference” is set by the stability of the Greenland and Antarctic ice sheets. His view on actions to mitigate climate change is that "halting global warming requires urgent, unprecedented international cooperation, but the needed actions are feasible and have additional benefits for human health, agriculture and the environment."

A minor controversy over his support for "objective" and "realistic" climate scenarios centers on what detractors call a justification for "extreme" scenarios in this quote:

"Emphasis on extreme scenarios may have been appropriate at one time, when the public and decision-makers were relatively unaware of the global warming issue, and energy sources such as “synfuels”, shale oil and tar sands were receiving strong consideration. Now, however, the need is for demonstrably objective climate forcing scenarios consistent with what is realistic under current conditions. Scenarios that accurately fit recent and near-future observations have the best chance of bringing all of the important players into the discussion, and they also are what is needed for the purpose of providing policy-makers the most effective and efficient options to stop global warming."

Censorship claim

In 2005 and 2006, Hansen claimed in interviews with the Washington Post[13] and the New York Times[14] that NASA administrators have tried to influence his public statements about the causes of climate change. Hansen claims that NASA public relations staff were ordered to review his public statements and interviews after a December 2005 lecture at the American Geophysical Union in San Francisco, claims which were denied by NASA administrator Michael Griffin.[citation needed]

James Hansen has also appeared on 60 Minutes[8] stating that the White House edited climate-related press releases reported by federal agencies to make global warming seem less threatening. He claimed that he was unable to speak "freely", without the backlash of other government officials. "In my more than three decades in the government I've never witnessed such restrictions on the ability of scientists to communicate with the public."

Hansen’s claims of censorship by NASA attracted the attention not only of the United States Congress and various media outlets, but also of several legal defense organizations. The 2006 George Soros Foundations Network Report detailed the work of the Open Society Institute (OSI) in conducting a “campaign on Hansen's behalf” run by “the Government Accountability Project (GAP), a whistleblower protection organization and OSI grantee.” The report indicated this campaign had “resulted in a decision by NASA to revisit its media policy .” The report further stated this campaign was prompted by the experience of Hansen who “protested attempts to silence him after officials at NASA ordered him to refer press inquiries to the public affairs office and required the presence of a public affairs representative at any interview.” [2]. Hansen addressed this specific issue publicly and in writing, saying he did “accept pro bono legal advice for a while” from GAP but did not receive any direct funds. [3].

Congressman Darrell Issa questioned Hansen's motivations in criticising the Bush administration, noting that he supported 2004 Democratic presidential candidate John Kerry and also received a $250,000 Heinz Environment Award from the Heinz Foundation, run by Kerry's wife, in 2001.[15] Hansen, who describes his political views as "middle-of-the-road conservative", stated in a 2004 speech at the University of Iowa that he would have preferred to vote for Republican John McCain had McCain been on the ballot, but settled for Kerry because of Kerry's stance on the climate change issue.[16]

Hansen has said that a global tipping point (also known as the runaway effect) will be reached by 2016 if the human population is unable to reduce greenhouse gases [17]. Hansen has said that IPCC scenarios for future sea level rise do not take into account ice sheet disintegration, which could cause several meters of sea level rise during the next century with unchanged climate forcings[18] .

There is a short clip in the 2006 documentary An Inconvenient Truth that shows Hansen being questioned by Al Gore on May 8, 1989, at what appears to be a Congress meeting. Gore criticizes Hansen for apparently contradicting himself in a written testimony on global warming. At that point, Hansen reveals that the last paragraph in the testimony was not written by him, but added by someone else.

Responsibility for climate change

Hansen notes that in determining responsibility for climate change, the effect of greenhouse gas emissions on climate is not determined by current emissions, but by accumulated emissions over the lifetime of greenhouse gases in the atmosphere. By this measure the U.S. will be the largest single cause of climate change even after its current emissions are surpassed by China and other developing countries.

On public policy, Hansen is critical of what he sees as efforts to mislead the public on the issue of climate change. He points specifically to the Competitive Enterprise Institute's commercials with the tagline "you call CO2 pollution, we call it life", and politicians who accept money from fossil fuel interests and then describe global warming as "a great hoax." He also says that changes needed to reduce global warming do not require hardship or reduction in the quality of life, but will also produce benefits such as cleaner air and water, and growth of high-tech industries.

Recent issues

Fast-feedback effects

In a paper published May 18, 2007[9], Hansen discussed the potential danger of "fast-feedback" effects causing ice sheet disintegration, based on paleoclimate data. The environmental and political activist George Monbiot summarises his findings as follows:

"The IPCC predicts that sea levels could rise by as much as 59cm this century. [19] Hansen’s paper argues that the slow melting of ice sheets the panel expects doesn’t fit the data. The geological record suggests that ice at the poles does not melt in a gradual and linear fashion, but flips suddenly from one state to another. When temperatures increased to 2-3 degrees above today’s level 3.5 million years ago, sea levels rose not by 59 centimetres but by 25 metres. The ice responded immediately to changes in temperature."[20]

It should be noted that Hansen stresses the uncertainties around these predictions:

"It is difficult to predict time of collapse in such a nonlinear problem ... An ice sheet response time of centuries seems probable, and we cannot rule out large changes on decadal time-scales once wide-scale surface melt is underway."[9]

Hansen concludes:

"Present knowledge does not permit accurate specification of the dangerous level of human-made GHGs. However, it is much lower than has commonly been assumed. If we have not already passed the dangerous level, the energy infrastructure in place ensures that we will pass it within several decades." [9]

Correcting Climate Record Database

In August 2007 blogger Stephen McIntyre noticed that many temperature records from the U.S. Historical Climatology Network (USHCN) displayed a discontinuity around the year 2000. NASA corrected the data and reported that "data for 2000 and later years were inadvertently appended to USHCN data for prior years without including the adjustments at these stations that had been defined by the NOAA National Climate Data Center."[21] The correction resulted in a slight (0.15 degree C) decrease in U.S. average temperatures post-2000, and 1934 replaced 1998 as the warmest year in the U.S. Note that the years have changed rankings before: in a 2001 paper 1934 was marginally warmer than 1998. Hansen argues that using yearly rankings in this way magnifies tiny differences, and that addition of new data to an analysis always causes values to fluctuate slightly. He further states that the difference between the 1934 and 1998 temperatures is insignificant and that the adjustment effect on the global temperature record is invisible.[22][23]

In a website commentary[22], Hansen indicated that he felt that Fox [News] and the Washington Times, among others, had overreacted to this mistake, stating that they had "gone bananas." Hansen quoted the United States Founding Fathers and a Native American mystic and argued that "The deceit behind the attempts to discredit evidence of climate change reveals matters of importance. This deceit has a clear purpose: to confuse the public about the status of knowledge of global climate change, thus delaying effective action to mitigate climate change", and that "The contrarians will be remembered as court jesters. There is no point to joust with court jesters ... The real deal is this: the ‘royalty’ controlling the court, the ones with the power, the ones with the ability to make a difference, with the ability to change our course, the ones who will live in infamy if we pass the tipping points, are the captains of industry, CEOs in fossil fuel companies such as EXXON/Mobil, automobile manufacturers, utilities, all of the leaders who have placed short-term profit above the fate of the planet and the well-being of our children."


  1. ^ Goddard Institute for Space Studies, NASA.
  2. ^ Goddard Space Flight Center.
  3. ^ James Hansen, Makiko Sato, Reto Ruedy, Andrew Lacis, and Valdar Oinas (16 June 2000). Global warming in the twenty-first century: An alternative scenario. Retrieved on 2007-09-27.
  4. ^ Rewriting The Science (CBS News)
  5. ^ Directory of the National Academy of Sciences. Retrieved on 2007-06-19.
  6. ^ The Heinz Awards. Retrieved on 2007-06-19.
  7. ^ James Hansen, Makiko Sato, Reto Ruedy, Andrew Lacis, Valdar Oinas (2000). "Global warming in the twenty-first century: An alternative scenario". Proceedings of the National Academy of Sciences 97 (18). Retrieved on 2007-09-27.
  8. ^ a b Catherine Herrick/Bill Owens (2006-03-19). Rewriting the Science. CBS.
  9. ^ a b c d e Hansen, James; et al. (2007). "Climate change and trace gases" (PDF). Phil. Trans. Roy. Soc. A 365: 1925 - 1954.
  10. ^ "Experts Find Possible Climatic 'Bomb'", Eleanor Randolph, Staff writer, Los Angeles Times, August 9, 1981, pg B3
  11. ^ Hansen, James; et al. (2000). "Global warming in the twenty-first century: An alternative scenario". Proc. Natl. Acad. Sci. 97: 9875-9880.
  12. ^ James Hansen (2003). Can We Defuse the Global Warming Time Bomb.
  13. ^ Juliet Eilperin (January 18, 2005). Putting Some Heat on Bush. Washington Post. Retrieved on 2007-06-20.
  14. ^ Andrew Revkin (January 29, 2006). Climate Expert Says NASA Tried to Silence Him. The New York Times. Retrieved on 2007-06-20.
  15. ^ J. R. Pegg. House Panel Investigates Bush's Climate Science Manipulations. Environmental News Service. Retrieved on 2007-09-27.
  16. ^ Policy or Politics? NASA Accused of Intimidating Climatologist
  17. ^ Earth's Climate Approaches Dangerous Tipping Point. Environmental News Service (June 1, 2007). Retrieved on 2007-06-29.
  18. ^ Hansen, James (2007). "Scientific reticence and sea level rise". Environ. Res. Lett. 2. doi:10.1088/1748-9326/2/2/024002.
  19. ^ Intergovernmental Panel on Climate Change (February 2007). Climate Change 2007: The Physical Science Basis - Summary for Policymakers. Table SPM-3..
  20. ^ George Monbiot (3 July 2007). A Sudden Change of State..
  21. ^ GISS Surface Temperature Analysis, August 2007 update
  22. ^ a b James Hansen, "The Real Deal: Usufruct & the Gorilla." August 2007. Hansen's response to his critics published on his web site.
  23. ^ Marc Kaufman. "NASA Revisions Create a Stir in The Blogosphere", The Washington Post, August 15, 2007, p. A6. Retrieved on 2007-09-25. 
  • Dr. James E Hansen's Homepage
  • NASA GISS Biography
  • James E Hansen timeline at the History Commons
  • The Global Warming Debate by James Hansen
  • "Scientist Inspires Anger, Awe for Challenges on Global Warming" Washington Post
  • "Climate Expert Says NASA Tried to Silence Him" New York Times
  • "NASA and Global Warming" Audio Interview with WBUR OnPoint
  • Soviet style "minder(s)" are being used on American scientists
  • 29 Jan 2006 Hansen in the New York Times
  • 13 Feb 2006 Time Magazine Cover Story: The Political Science Test
  • Sequence of stories in The New York Times, from January to July 2006, exposing political interference with climate scientists at NASA"

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "James_Hansen". A list of authors is available in Wikipedia.
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