As I mentioned previously, global warming is the scientific consensus. It is, moreover, well established that anthropogenic sources of CO² are the primary cause of rising global temperatures. Rising temperatures and other effects associated with increased atmospheric CO² are driving changes in our global climate. Some foreseen, and others unexpected. As other nation’s climb on-board our economic train wreck, CO² emissions continue to increase, and global warming is accelerated.

Sometimes it is too easy to brandish the words “scientific consensus” with the hope that it will silence critics or lend an air of impenetrable authority to an argument. It is often the case that the general public is not well aware of the process by which scientific consensus is achieved. So, what is scientific consensus? How is it established?

Wikipedia has an excellent article on the scientific opinion on climate change. This article lists several polls and studies conducted by various research groups, several of which cast doubt on the concept of a human-induced warming trend. In 1993, for example, a Heartland Institute publication explained:

A Gallup poll conducted on February 13, 1992 of members of the American Geophysical Union and the American Meteorological Society – the two professional societies whose members are most likely to be involved in climate research – found that 18 percent thought some global warming had occurred, 33 percent said insufficient information existed to tell, and 49 percent believed no warming had taken place.

It turns out that between 1998 and the present the Heartland Institute has received over $500,000 in grants from none other than Exxon Mobile. Naturally, the Heartland Institute continues to publish documents of dubious scientific merit, insisting that global warming is a “liberal hoax”. Ok, so maybe the Exxon money has interfered with their objectivity a little bit.

But what about the 1997 survey conducted by the policy advocacy group Citizens for a Sound Economy? This survey states that:

By a 44 to 17 percent margin, climatologists say that “recent global warming is a largely natural phenomenon,” while nine out of 10 of the climatologists surveyed agreed that “scientific evidence indicates variations in global temperature are likely to be naturally-occurring and cyclical over very long periods of time.”

Oh, wait a minute, this group has also received over $380,000 from Exxon Mobile since 1998. Kind of hard to take them seriously too.

More serious scientific publications have reached a different conclusion. In 2001 the Intergovernmental panel on climate change released its Third Assessment Report, concluding:

1. An increasing body of observations gives a collective picture of a warming world and other changes in the climate system (The global average surface temperature has increased over the 20th century by about 0.6°C; Temperatures have risen during the past four decades in the lowest 8 kilometers of the atmosphere; Snow cover and ice extent have decreased)
2. There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities
3. Human influences will continue to change atmospheric composition throughout the 21st century

Since the IPCC publication, many other prestigious scientific associations have issued statements expressing agreement and concern regarding the IPCC consensus: the National Research Council (2001), the American Meteorological Society (2003), the national science academies of the G8 nations (2005), and the Federal Climate Change Science Program (2006).

In my mind, the real watershed publication that firmly established global warming within the realm of overwhelming scientific evidence came with Naomi Oreskes’ publication in Science Magazine on December 3, 2004. Oreskes set out to test the hypothesis that these types of reports and statements may in fact involve the “downplay of legitimate dissenting opinions.”

That hypothesis was tested by analyzing 928 abstracts, published in refereed scientific journals between 1993 and 2003, and listed …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.

I’m not a climate scientist, but I have participated in the peer review process, and though it is not without flaws, it warrants our respect as one of the primary processes by which scientific research is validated and accepted. Oreskes’ research suggests that global warming, within the context of peer reviewed publications, has moved beyond consensus and into the realm of unanimity. Further research would be required, however, to ascertain whether this statement is true.