In una risoluzione del 18 Novembre 2007, l' American Physical Society (APS) dichiarava:
“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.”
— APS News; January 2008 (Volume 17, Number 1)
Qualche mese fa, alcuni membri dell' APS hanno presentato una petizione chiedendo al Consiglio APS di cambiare la risoluzione e di sostituirla con la seguente (che nega la gravità dei cambiamenti climatici, nega gli effetti antropici su di essi e addirittura valuta positivamente gli incrementi di CO_2 in atmosfera):
Greenhouse gas emissions, such as carbon dioxide, methane, and nitrous oxide, accompany human industrial and agricultural activity. While substantial concern has been expressed that emissions may cause significant climate change, measured or reconstructed temperature records indicate that 20th 21st century changes are neither exceptional nor persistent, and the historical and geological records show many periods warmer than today. In addition, there is an extensive scientific literature that examines beneficial effects of increased levels of carbon dioxide for both plants and animals.
Studies of a variety of natural processes, including ocean cycles and solar variability, indicate that they can account for variations in the Earth’s climate on the time scale of decades and centuries. Current climate models appear insufficiently reliable to properly account for natural and anthropogenic contributions to past climate change, much less project future climate.
The APS supports an objective scientific effort to understand the effects of all processes – natural and human --on the Earth’s climate and the biosphere’s response to climate change, and promotes technological options for meeting challenges of future climate changes, regardless of cause.
Il Presidente dell' APS ha successivamente nominato un Comitato di scienziati incaricandolo di esaminare la controversia. Dopo quattro mesi di lavoro, il Comitato ha suggerito che la petizione fosse respinta e che la risoluzione originale fosse mantenuta. L' 8 Novembre il Consiglio APS ha votato, recependo le indicazioni del Comitato. Esistenza e gravità dei cambiamenti climatici sono inequivocabili secondo l' APS.