I just don't understand the reasoning of the many who call themselves climate change skeptics.

Let's pretend it's not about earth, for a moment, and just some black box, hovering in a vacuum, with a big lightbulb shining next to it. Practically all its energy comes from the lightbulb (the rest from the residual heat within, and some dim source of central power), and practically all of its cooling consists in radiating infrared back outward. Now you put a layer of glass, which infrared cannot penetrate, over the black box, and wait, and see what happens.

The infrared is significantly absorbed by the glass, largely radiated back to the box, and thus the largest channel for cooling -- and pretty much the only one that will work over a long period of time -- has been attenuated.

Now replace the black box by earth, the lightbulb by the sun, and the glass by CO2.

The black box would have to be totally weird in order to keep from heating up. It might, for some time, somehow redirect some of the heat into less observable sections of its mass (e.g. the lower levels of the earth's oceans, which have a much greater heat capacity than its atmosphere), but this cannot last forever. It might also become more reflective, absorbing less light (e.g. the earth's clouds, desertification)? Except clouds are totally observable, and an opposite effect comes from the melting snows and ice caps and constructed asphalt we add in urban areas: all of which have radiance and albedos observable from the outside (e.g. our satellites). Finally, the black box radiation is proportional to the fourth power of the temperature, so even if the percentage of radiated power that reaches the outside of the glass is diminished, if the temperature of the primary radiative bodies becomes less even, such that ∫T(new)^4 dA &gt;&gt; ∫T(old)^4 dA, the temperature can stay roughly constant. Other than that, there's close to nothing that can be done: that box will very probably rise in temperature, and almost certainly the climate will change.

Skeptics correctly points out that the lightbulb varies in power output. And the black box is moving a bit relative to the light -- further away or closer by -- shinier or cooler or more black parts facing the light at any given time. They also point out that the glass isn't the only thing surrounding the black box -- for example they have noticed also a shiny layer of dust on the glass (aerosols), and an even bigger layer of glass underneath the glass we'd place (water vapor). And they point out that the layer of black paint appears to be, in a great proportion, liquid, and with a high heat capacity, and churning cyclically, and that there's a lot of it, so that in any one instance a cooler or a warmer parcel of that liquid is showing.

None of this changes a thing about the fact that if we put yet another layer of glass on the box, the smart money is on it heating, and certainly on it changing. How could it not? At this point the onus is totally on these climate change skeptics to suggest a means by which the box is supposed to stay exactly the same.

Which brings up an interesting point. Maybe it is not so necessary that the Earth stays the same. Maybe there are credible arguments that explain that, really, the box won't change that much, and for the teeming, glass manufacturing cultures of microbes living under the glass that these changes are not really such a big deal.

Some scientists, who I respect very much -- Freeman Dyson for example, make this very argument. I respectfully disagree with him, as I think that there's far too much risk in disrupting the biosphere, and that the disruption, famine, and loss of ecosystems and species that have already occurred are too great a price to pay, that oil wars, tyrannies, and people dying of respiratory illness from coal plants aren't exactly positive either, and estimates of the probability of some catastrophic event happening, like say, Greenland melting, the consequences of which are too dire to imagine, range somewhere between 10% and 80%.

But that's a philosophical disagreement. What we have with 'skeptics' is a scientific disagreement: the great majority say either that it is happening, but only as part of natural variation, and they had nothing to do with it, or that it isn't happening at all. Which, at this point, seem more like the antics of a child screaming 'I didn't do it,' or putting their hands to their ears, singing 'la la la, I can't hear you!' than of a calm and reasoned scientist -- or skeptic -- examining the assumptions of a majority opinion. Their conclusions are already drawn.