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.K. is still the largest single cause of climate change, followed by the U.S. and Germany, even though its current emissions are surpassed by the Peoples Republic of China.
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.
“Burning of fossil fuels, primarily coal, oil and gas, increases the amount of carbon dioxide (CO2) and other gases and particles in the air. These gases and particles affect the Earth’s energy balance, changing both the amount of sunlight absorbed by the planet and the emission of heat (long wave or thermal radiation) to space. The net effect is a global warming that has become substantial during the past three decades. Global warming from continued burning of more and more fossil fuels poses clear dangers for the planet and for the planet’s present and future inhabitants. Coal is the largest contributor to the human-made increase of CO2 in the air. Saving the planet and creation surely requires phase-out of coal use”. 
“Practically, I don't see how we can stop putting the oil in the atmosphere, because that's owned by Russia and Saudi Arabia,” he advised the House Committee on Global Warming. “We can make our vehicles more efficient, but that oil is going to get used and it's going to get in the atmosphere . . . and it doesn't really matter much how fast we burn it. But what we could do is stop the coal.” 
In 2007 testimony against the construction of new coal-fired power plants lacking carbon capture and storage technology, he stated “If we cannot stop the building of more coal-fired power plants, those coal trains will be death trains – no less gruesome than if they were boxcars headed to crematoria, loaded with uncountable irreplaceable species.”
A 2008 document authored by Hansen and eight other scientists, entitled “Target Atmospheric CO2: Where Should Humanity Aim?” calls for phasing out coal power completely by the year 2030 .
 Censorship controversy
In 2005 and 2006, Hansen stated in interviews with ABC News, The Washington Post, and The New York Times 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.
James Hansen has also appeared on 60 Minutes 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”. 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.
Congressman Darrell Issa questioned Hansen's motivations in criticizing the Bush administration, noting that Hansen 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. 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.
Hansen has said that a global tipping point will be reached by 2016 if the human population is unable to reduce greenhouse gases. 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.
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 Senate hearing. 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.
Two years after James E. Hansen and other agency employees described a pattern of distortion and suppression of climate science by political appointees, the agency’s inspector general report said “our investigation found that during the fall of 2004 through early 2006, the NASA Headquarters Office of Public Affairs managed the topic of climate change in a manner that reduced, marginalized or mischaracterized climate change science made available to the general public.”
For a detailed examination of the Hansen censorship controversy, see Censoring Science: Inside the Political Attack on Dr. James Hansen and the Truth of Global Warming, by Mark Bowen.
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Nel 2005 e nel 2006, Hansen ha dichiarato nel corso di interviste con ABC News, The Washington Post e The New York Times che la NASA gli amministratori hanno cercato di influenzare le sue dichiarazioni pubbliche in merito alle cause del cambiamento climatico.    Hansen crediti NASA che il personale di pubbliche relazioni sono state ordinate per rivedere il suo pubblico di dichiarazioni e interviste dicembre 2005 dopo una lezione presso l'American Geophysical Union di San Francisco.
Egli ha sostenuto che non era in grado di parlare “liberamente”, senza il contraccolpo di altri funzionari del governo. “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.” [ 25 ] “Nella mia più di tre decenni al governo non ho mai assistito a tali restrizioni sulla capacità degli scienziati di comunicare con il pubblico.”