Right Image Source: University Corporation for Atmospheric Lab.
Top Left Image Source: NASA
From time to time it is helpful to refer someone to a readily available online source of reliable and objective information about climate change science. There are many sources from which to choose, but there is one that appears to clearly take the honors when it comes to objectivity and integrity. That source is the National Research Council (NRC). The National Research Council was formed by the National Academies of Sciences, and regarding the National Academies, here's a brief statement from the "About Us" portion of their website.
"The National Academy of Sciences (NAS) was signed into being by President Abraham Lincoln on March 3, 1863. As mandated in its Act of Incorporation, the Academy has, since 1863, served to "investigate, examine, experiment, and report upon any subject of science or art" whenever called upon to do so by any department of the government"
The National Academies formed the National Research Council in 1916 "...to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government."
So without further elaboration, here is the link to a concise summary of the best available understanding of climate change science as of the current year, 2012. Enjoy!
CLIMATE CHANGE: Evidence, Impacts, and Choices
Answers to common questions about the science of climate change