OK so far. I did not know that weather could operate at such a large time period; no wonder climate scientists are always saying weather =/= climate whenever people bring up cold winters.
well, there are things that result in quite drastic weather changes over the course of several years (e.g., El Nino / La Nina) that arguably are climate oscillations. For our debate here, however, that's not relevant, so I'd like to count such things as weather, too (and mention when they threaten to screw decade-long means or so). For example, January to October 2010 was very warm worldwide because of El Nino, then a very strong La Nina came in and ruined all predictions based on a continued El Nino (but, to answer your previous criticism further, e.g., the UK Met Office had made a prediction explicitly saying that 2010 will be warmest if El Nino continues, but that a La Nina could make is less warm than earlier years. Denialists conveniently ignored the caveat and yelled foul play later.)
Another example of "weather" as far as we are concerned is Arctic oscillation, which was responsible for the very cold last winter in NA and Europe (but the rest of the world got roasted, so the global average was high). Do we care for that when we talk climate? Obviously yes, if we talk about the weather we will have in a few decades, or the climate in a specific place. But for the general pattern worldwide it doesn't really matter much. So we had (almost unusually) cold weather, Australia had very warm weather.
let's continue:
11) climate has varied strongly throughout Earth's history
12) the overall balance of energy on earth can be affected by changes in incoming energy and outgoing energy.
13) the physical properties and processes relating to climate have not changed (i.e., there is no mystery chemical that was doing something to climate that today does not exist anymore, so other such nonsense). Processes in the past can be expected to repeat themselves today if the same conditions exist.
14) Most gases present in the atmosphere are not influenced by radiation (i.e., we can ignore them), including nitrogen, oxygen, noble gases.
15) others, especially CO2, methane and water vapor, absorb infrared radiation
16) these gases show the ability to absorb IR radiation not only in the lab, but also in the atmosphere, keeping energy in the atmosphere that would, if no or a reduced amount of the gases were present, be given off into space. This is termed greenhouse effect.
17) an increased greenhouse effect leads to warming, a reduced one to cooling, because more / less energy is retained.
OK so far? if you are not sure about any point (e.g., is Co2 a greenhouse gas?), just say so!