I agree with: “a body reaches thermal equilbrium with its environment by shedding excess heat, through radiation, conduction and convection.”

I agree with: “as excess heat goes into the atmosphere and oceans, there will be changes in ecosystems and in the earth’s mechanisms for redistributing heat (weather and climate, ocean currents).”

Disagree.with "the earth can only eliminate heat by radiating it as excess thermal infrared radiation into space, or by reflecting sunlight from the cloud tops and the ice caps."

Since outer space is a vacuum, the fast moving gas particles that exist in the thermosphere, can and do escape the Earth’s gravitational influence. See: http://science.nasa.gov/science-news/science-at-nasa/1997/ast09dec97_3/

The escaping gas experiences the Joule expansion effect and the upper atmosphere cools. See: http://en.wikipedia.org/wiki/Joule_expansion

Eventually the escaping gasses cause the atmospheric density to become significantly lower, allowing more radiation from the sun to impinge on the surface of the planet.

Why would this heating happen now and not before the “atomic age”?
My suspicion is that the information in the following web sites may indicate the beginning of the problem.

http://www.johnstonsarchive.net/nuclear/hane.html
http://adsabs.harvard.edu/full/1964IAUS...18...47O
http://en.wikipedia.org/wiki/High-altitude_nuclear_explosion

As I see it, there is as much carbon and oxygen on Earth as there always has been, why is carbon considered a bad guy all of a sudden?

I suspect that these global changes in the environment (including the melting of the ice) is caused by the addition of radionuclides from various sources, spread into the environment they cause heating, among other bad effects..