Spoken language can be confusing because you can have words which sound exactly the same but mean totally different things. Such words are called homophones, as found in this section title. At the very least, and if you’re very familiar with the language in question, the differentiation is implicitly understood given the context. If you don’t understand the language that well then help is provided by a differentiation of the spelling, but this doesn’t help if you’re not reading it.
Bass Lead Wind
Things can get even more confusing for first-time literates when the words don’t sound the same but are spelled the same: I caught the bass by singing bass (whatever works I guess!); Lead the bird to fill it with lead; Wind the coil in the wind. These words are called homographs.
The Greenhouse Effect The Greenhouse Effect
There are two versions of “the greenhouse effect” and, obviously, they use both the same spelling and the same pronunciation. Such words (or phrases I guess) are called homonyms. However, few people are aware of any distinction in the case of “the greenhouse effect”. Let us enlighten ourselves, therefore.
The first version of the greenhouse effect is that which is found in a real greenhouse. For, why would we have such a thing called “greenhouse effect” if it weren’t for the behaviour of a real greenhouse? This version of the greenhouse effect comes out of traditional science and physics and denotes the effect found typically inside a glass-ceiling greenhouse where the ceiling prevents what would have been natural atmospheric convection, otherwise found in the open atmosphere. That is, when a surface is heated, the air in contact with it heats by conduction (and radiation but generally this is a much weaker component of the heating at the contact boundary between the surface and the air), and then the warm air rises because it is less dense, and cool air falls from above to replace it. This is a natural and automatic process in the open atmosphere. A real greenhouse prevents convection because it traps the warmed air inside the enclosure and in contact with the surface heating it; the warm air is unable to ascend away and cool air is unable to descend and replace it, because of the glass roof. Thus, the air inside the greenhouse continues to rise in temperature, and the maximum temperature that could theoretically be achieved inside the real greenhouse is the temperature of the maximum solar heating being absorbed by and within the greenhouse. Any gas trapped inside a real greenhouse can be considered a “greenhouse gas”, although the term is rather passive, and moot.
The second version of the greenhouse effect is that postulated by climate science, and it is an alternative description of the warming process known for a real greenhouse. In this second version, a real greenhouse and the open atmosphere operate the same way, rather than the opposite way. Instead of warm air being trapped, the alternative “climate science greenhouse effect” says that radiation is trapped, and since radiation is trapped then the inside must get warmer than the outside. The same process happens in the atmosphere because “greenhouse gases” trap radiation just like the ceiling of the real greenhouse traps radiation. In this case, the temperature inside the greenhouse can become hotter than the maximum solar heating temperature. That is important for the climate science greenhouse effect because climate science thinks that the solar input to the Earth is too cold to ever heat anything above -18C in temperature on its own.
Now that we’ve learned about the two types of greenhouse effect – the one for the real greenhouse and the alternative one for climate science – it would be nice to label them differently so that they are easier to distinguish and put into the correct context. Since the greenhouse effect of a real greenhouse is about trapping air, which is physical material, let’s call the greenhouse effect of a real greenhouse the “physical greenhouse effect“. And then, since the alternative greenhouse effect of climate science is about trapping radiation, let’s call it the “radiative greenhouse effect“.