CC4.1. How has the debate changed over decades?

The first point Jim Hansen made to Congress back in 1988 was, “the globe is heating up.”  Let’s look closely at the scientific process in action by examining how the debate around this question has changed since then.  Has the scientific community come to consensus on that point?  This investigation is meant to hone your critical thinking.



Two different colors of index cards, sticky-note paper, or sheets of paper.

Article excerpts to read:

1989: S.F. Forum on Global Warming Hears Heated Scientific Debate. By Charles Petit, The San Francisco Chronicle

1999: Earth’s Temperature Shot Skyward in 1998. By Richard Monastersky, Science News

2000: Record Breaking Temperatures Seen As Possible Evidence of Faster Rate of Global Warming, NOAA Reports See original web page.

2005: World Temperatures Keep Rising with a Hot 2005. By Juliet Eilperin, Washington Post

2010: The New Normal?: Average Global Temperatures Continue to Rise – 2010 may prove to be the hottest year since record keeping began in 1880. By David Biello  | July 22, 2010 | 65 | Scientific American

Find more recent articles in the GSS Staying Up To Date pages.

What To Do

  1. Divide the news and magazine articles among your group members.
  2. On sheets of paper or index cards write the following dates in bold:  1985, 1990, 1995, 2000, 2010.  Spread these  out on a table or the floor to create a timeline.
  3. Search for statements that support and statements that oppose Hansen’s claim that “the globe is heating up.”  Put those statements colored paper, cards, or sticky-notes — use one color for supporting statements and another color for opposing statements. On the back, write the source of the information or the person or agency that made the statement. 
  4. Place each statement on the proper place on the timeline, statement-side-up.
  5. Discuss the following questions and write brief answers to them:
    a. What changes do you see in the information 
        as time goes by?
    b. At what point do you think the majority of 
        scientists agreed with Hansen’s original statement? 
    c. What do you think swayed the scientific community 
        toward consensus on the question of whether or 
        not the globe is heating up?
  6. Now flip all the statements over so that the source/person/agency side is face up. 
    Discuss and write answers to these questions:
    a. Do you see any scientist’s name appearing on 
        two different colored cards? 
        When did the change happen?  
        What do you think caused the change?
    b. What do you think these observations say about the 
        scientific process and/or the scientists?


Compare and contrast just the 1989 and 1999 articles.  Answer these questions:

Tim Barnett

In the 1989 article…

  • i. Imagine you’re in the audience in San Francisco when the scientists made their 1989 presentations. James Hansen is not quoted in the 1989 article. Based on the descriptions in the article and earlier in this chapter what do you think he said?
  • ii. What do Tim Barnett and James Hanson agree about? What do they disagree about?
  • iii. What does Tim Barnett mean by the statement, “Global averages [are] an absolutely bogus concept”?
  • iv. On what basis does Thomas Karl disagree with Hanson? What does Hanson say about Karl’s analysis?
  • v. Based on this article, as of 1989, did most scientists believe global warming was under way?

Tim Barnett

James Hanson

In the 1999 article…

  • vi. Has the data collected between 1989 and 1999 more strongly supported Hanson or Karl and Barnett?
  • vii. What disagreements are cited in this article?
  • viii. Based on this article, as of 1999, did most scientists believe global warming was under way?
  • ix. In your opinion, were Hansen’s conclusions justified at the time? 
  • x. Does the evidence support his views today?

James Hansen