The American Physical Society on November 18, 2007, adopted the following policy:
Emissions of greenhouse gases from human activities are changing the atmosphere in ways that affect the Earth's climate. Greenhouse gases include carbon dioxide as well as methane, nitrous oxide and other gases. They are emitted from fossil fuel combustion and a range of industrial and agricultural processes.
The evidence is incontrovertible: Global warming is occurring. If no mitigating actions are taken, significant disruptions in the Earth’s physical and ecological systems, social systems, security and human health are likely to occur. We must reduce emissions of greenhouse gases beginning now.
Because the complexity of the climate makes accurate prediction difficult, the APS urges an enhanced effort to understand the effects of human activity on the Earth’s climate, and to provide the technological options for meeting the climate challenge in the near and longer terms. The APS also urges governments, universities, national laboratories and its membership to support policies and actions that will reduce the emission of greenhouse gases.
It is indicative of our times that a learned society, whose founding mission was "to advance and diffuse the knowledge of physics", has no qualms with adopting a policy that includes the phrase "The evidence is incontrovertible". Any scientist will tell you that nothing is incontrovertible. A number of people thought that this policy was not acceptable and wrote an open letter to the APS urging the council to revise its policy on climate change, see here.
On the 22 July, 2009, the weekly journal Nature published the following letter from six APS members (one can only see the version in Nature if one subscribes)
Petitioning for a revised statement on climate change
By S. Fred Singer, Hal Lewis, Will Happer, Larry Gould, Roger Cohen & Robert H. Austin
We write in response to your issue discussing “the coming climate crunch”, including the Editorial ‘Time to act‘ (Nature 458, 10771078; 2009). We feel it is alarmist.
We are among more than 50 current and former members of the American Physical Society (APS) who have signed an open letter to the APS Council this month, calling for a reconsideration of its November 2007 policy statement on climate change (see open letter at http://tinyurl.com/lg266u; APS statement at http://tinyurl.com/56zqxr). The letter proposes an alternative statement, which the signatories believe to be a more accurate representation of the current scientific evidence. It requests that an objective scientific process be established, devoid of political or financial agendas, to help prevent subversion of the scientific process and the intolerance towards scientific disagreement that pervades the climate issue.
On 1 May 2009, the APS Council decided to review its current statement via a high-level subcommittee of respected senior scientists. We applaud this decision. It is the first such reappraisal by a major scientific professional society that we are aware of, and we hope it will lead to meaningful change that reflects a more balanced view of climate-change issues
That the society is reviewing the statement is wonderful news.
The Royal Society, an institution that is even more venerable than the APS, is a proponent of climate change which has prompted Rupert Wyndham to write a letter to the society's president, Lord Rees. You can read it here. Unfortunately, I don't think we will see a similar review of the Royal Society's stance.