• Why did it take so long for global warming to be widely acknowledged? There have been some suggestions that the causes are linked more strongly to political motivations than to the evidence. Chris Mooney is a Washington correspondent for Seed Magazine, which is a magazine that reports on science issues. In his The Republican War on Science published in 2005, he considers ways in which he believes that political motives have distorted reporting on science and led to public misunderstanding of key issues. Was this what happened in the case of global warming? It is clear that if global warming is occurring and is being caused by greenhouse gases then curbing the burning of fossil fuels (gasoline) and taking other measures to limit these gases could have a profound effect on the American economy. Is this one of the reasons why the U. S. seems to have been slow to respond to environmental concerns that have been worrying those in other countries for quite some time?
  
  Chris Mooney's The Republican War on Science.
  Daniel Kevles review of Chris Mooney's book.
  
• An Inconvenient Truth, Al Gore's movie, also suggests that there had been a systematic effort to mislead the press and the ultimately the public about scientific opinion on global warming. The primary evidence for this claim is that while papers published in scientific journals were in agreement both on global warming and on its primary causes (greenhouse gases), the popular press was portraying the scientific community as divided on the issue. The website for the movie presents advertisement, promotion of activism to address the problem, and a calculator which indicates how much CO2 you produce a year. Though there is a clear point of view expressed on this website, there is also a lot of information.
  
• Another interpretation is that the information that is available is incomplete and until recently inconclusive (though the evidence presented in An Inconvenient Truth would seem to count against this explanation). Perhaps the public confusion was the result of uncertainty within the scientific community. Reasonable people may have been disagreeing because of incomplete data and legitimate questions about how the data should be interpreted. There surely is some truth to this, but we need to be careful and recognize that though there are disputes within the scientific community about many things, including some issues related to global warming, these disputes do not in themselves invalidate what we do know. A good place to start understanding what we do and do not know is The Basics of Climate Prediction.
  
• Whatever conclusion you draw about the possible motivations behind the shaping and control of information about global warming, the RealClimate blog is a good source of up-to-the minute information on climate issues. The contributors to this blog are themselves climate scientists. They offer links to sources, dispel common misunderstandings, and refute poor arguments about the issues.
  

Global warming: Debates about the science

Scientists do not always agree and there are a variety of different levels at which their disputes can take place:

A. They might disagree about what the evidence shows or to what degree it supports the hypothesis.
Example: The major disagreements are about the rate at which global change is occurring. The scenarios range from catastrophic abrupt change to a gradual shift in temperature over the next 100 or so years.

B. They might disagree about what the evidence is. This could be a disagreement about how to interpret the data, about the accuracy of the data, or a disagreement about what data is relevant.
Example: John Christy, a University of Alabama climatologist argued in 2004 (and earlier) that he had data that showed that the atmosphere was cooling rather than warming. In August 2005, two other scientists pointed out problems with the data set that Christy had used. In 2004, Christy testified before congress that global warming was not the problem that many climatologists were making it out to be. His argument was based on this disputed data set. Interestingly, Christy is on record as supporting the majority view that global warming is taking place and is at least contributed to by CO2. For links to the discussion of this issue see RealClimate.

Another example: Is the Antarctic climate changing?

C. They might agree that the hypothesis is supported by the evidence but disagree about what the hypothesis might explain or predict. This could be a disagreement about the scope of the hypothesis or the degree of precision with which it should be interpreted.
Example: Though scientists agree about the general fact of global warming and its causes, they might disagree about whether some particular phenomena are caused by or related to global warming. So, for instance, they might dispute that the increase in hurricanes is due to global warming (or, even more specifically, they might dispute that global warming caused Hurricane Katrina). See this RealClimate also.

It is important to keep in mind that disagreements among scientist do not mean that we really don't know anything. We know quite a bit and disagreement is not surprising when the data are difficult to obtain and require interpretation. Also, it is important to remember that much of our knowledge is probabilistic, that is, we have a high degree of confidence that we are right but we are not certain. The standard of certainty is not the norm for scientific knowledge and so should neither be expected nor required. See The Nature of Science and Statistical Reasoning.