John Vechey of PopCap Games recently joined The Motley Fool for a climate change summit. His first panel guests were Dr. Rachel Cleetus and Dr. Joe Casola. Rachel is a Climate Economist with the Union of Concerned Scientists, where she advocates for effective global warming policies at the state, regional, federal, and international levels. Joe is Program Director for Science and Impacts at the Center for Climate and Energy Solutions (C2ES), which works to assess the current state of knowledge regarding climate change and its impacts, and to promote actions that strengthen climate resilience.

Rachel defines "skepticism," and what it does and does not mean in the climate change "debate." There are some valid issues and questions to be asked regarding climate science -- Joe shares several of them -- but the fact of global warming, and humanity's role in causing the change, are not among them. Their message is important pushback against companies like ExxonMobil (NYSE:XOM), which spend heavily on efforts to deny climate science in the public domain. With growing momentum behind efforts to deal with the climate change threat, ExxonMobil may find itself on the wrong side of history.