As with all polls, the answers you get depend on the questions you ask. We found that almost all climate scientists believe that the world has been warming: 97% agree that “global average temperatures have increased” during the past century. But not everyone attributes that rise to human activity. A slight majority (52%) believe this warming was human-induced, 30% see it as the result of natural temperature fluctuations and the rest are unsure.
When it comes to current conditions, however, the consensus in favor of human warming reemerges: 84% believe “human-induced greenhouse warming” is now occurring, compared with only 5% who reject this conclusion. And 74% say the “currently available scientific evidence substantiates” its occurrence, while only 9% disagree. So global warming doubters are a genuinely small minority among American climate scientists; it is difficult to believe that any transgressions against scientific procedures or the scientific ethos uncovered by Climategate are going to change that.
In a recent survey of more than 3,000 Earth scientists, 82% agreed that human activity is a “significant contributing factor” in changing global temperatures. Specialists were in greater agreement: 75 of the 77 climate scientists who actively publish in the field about 97% agreed with the statement.
The American Meteorological Society, the American Geophysical Union, and the American Association for the Advancement of Science (AAAS) all have issued statements in recent years concluding that the evidence for human modification of climate is compelling.
The drafting of such reports and statements involves many opportunities for comment, criticism, and revision, and it is not likely that they would diverge greatly from the opinions of the societies’ members. Nevertheless, they might downplay legitimate dissenting opinions. That hypothesis was tested by analyzing 928 abstracts, published in refereed scientific journals between 1993 and 2003, and listed in the ISI database with the keywords “climate change.”
The 928 papers were divided into six categories: explicit endorsement of the consensus position, evaluation of impacts, mitigation proposals, methods, paleoclimate analysis, and rejection of the consensus position. Of all the papers, 75% fell into the first three categories, either explicitly or implicitly accepting the consensus view; 25% dealt with methods or paleoclimate, taking no position on current anthropogenic climate change. Remarkably, none of the papers disagreed with the consensus position.
Admittedly, authors evaluating impacts, developing methods, or studying paleoclimatic change might believe that current climate change is natural. However, none of these papers argued that point.
This analysis shows that scientists publishing in the peer-reviewed literature agree with IPCC, the National Academy of Sciences, and the public statements of their professional societies. Politicians, economists, journalists, and others may have the impression of confusion, disagreement, or discord among climate scientists, but that impression is incorrect.
This brief report addresses the two primary questions of the survey, which contained up to nine questions (the full study is given by Kendall Zimmerman ):
1. When compared with pre-1800s levels, do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?
2. Do you think human activity is a significant contributing factor in changing mean global temperatures?
With 3146 individuals completing the survey, the participant response rate for the survey was 30.7%. This is a typical response rate for Web-based surveys [Cook et al., 2000; Kaplowitz et al., 2004]. Of our survey participants, 90% were from U.S. institutions and 6% were from Canadian institutions; the remaining 4% were from institutions in 21 other nations. More than 90% of participants had Ph.D.s, and 7% had master’s degrees. With survey participants asked to select a single category, the most common areas of expertise reported were geochemistry (15.5%), geophysics (12%), and oceanography (10.5%). General geology, hydrology/hydrogeology, and paleontology each accounted for 5–7% of the total respondents. Approximately 5% of the respondents were climate scientists, and 8.5% of the respondents indicated that more than 50% of their peer-reviewed publications in the past 5 years have been on the subject of climate change. While respondents’ names are kept private, the authors noted that the survey included participants with well-documented dissenting opinions on global warming theory.
Results show that overall, 90% of participants answered “risen” to question 1 and 82% answered yes to question 2. In general, as the level of active research and specialization in climate science increases, so does agreement with the two primary questions (Figure 1). In our survey, the most specialized and knowledgeable respondents (with regard to climate change) are those who listed climate science as their area of expertise and who also have published more than 50% of their recent peer-reviewed papers on the subject of climate change (79 individuals in total). Of these specialists, 96.2% (76 of 79) answered “risen” to question 1 and 97.4% (75 of 77) answered yes to question 2….