Every scientist, every science teacher, and possibly every gardener in the world knows that applying the terms ‘greenhouse effect’ and ‘greenhouse gases’ to the atmosphere, and to climate, is the most basic bunkum. Why then do we continue to propagate these two terms which are scientifically wrong and so misleading? Or, for some, does their propaganda value make the science irrelevant? It is no wonder that a physics teacher whom I met recently at one of our top schools was in despair: “How can we teach the kids real science if such nonsense is allowed into the curriculum?”

Wot No Convection!

So, back to basics. The atmosphere does not work like a garden greenhouse. In the simplest of terms, a greenhouse functions because the in-coming solar radiation - the sun - warms the soil, the tables, the plants, and the pathways inside it, which then, in turn, warm the air trapped within the closed greenhouse environment [remember that there is very little direct solar heating of the air]. The air then continues to remain warm because it is trapped within the closed greenhouse so that the heat cannot be lost through the process of convection, unlike in the air outside the greenhouse and in the atmosphere, where free convection is uninhibited. If you want to test this, or to cool your greenhouse, you must open the door, or, preferably, a window or two in the greenhouse roof, to permit convection to occur. Greenhouses work, first and foremost, because they prevent the normal processes of convection, not because of radiative forcing, precisely the opposite of what happens in the open atmosphere.

Our Radiative-Convective Atmosphere

Thus, the down-to-earth greenhouse effect does not, and can not, apply to the atmosphere, which experiences free convection. Indeed, so true is this fact that any complex model relating to climate must take it into account, so that we are not even dealing with a purely radiative effect, but with a much more complex, and still very little understood, set of radiative-convective effects. In essence, the ‘opacity’ of the atmosphere to outgoing infrared radiation determines the height from which most photons will be emitted into space. The more ‘opaque’ the atmosphere, the more the escaping photons will be emitted from higher in the atmosphere, and, because the emission of infrared radiation is a function of temperature, it is the temperature of the atmosphere, at this emission level, that will be determined by the requirement for the emitted flux to balance the absorbed solar flux.

We must further take into account the standard fact that the temperature of the atmosphere decreases with height at a rate of c. 6.5 °C per kilometer (on average), until the Stratosphere is attained (between 8 - 16 km above the surface) [we can assume for this purpose that the lapse rate is fixed by non-radiative energy fluxes]. If we then determine the temperature (and height) at the emission level of the infrared flux escaping into space, the surface temperature can be computed by increasing temperature at the rate of 6.5 °C per kilometer - the above-mentioned environmental lapse rate, reversed - until one reaches the surface. Thus, the more ‘opaque’ the atmosphere, the higher will be the emission level of the escaping infrared radiation, and, consequently, the warmer the surface, since the lapse rate will occupy a longer distance in the vertical.

But, all this is going much farther than I need.

The point is ever so simple. The atmosphere - carbon dioxide, methane, whatever - does not function like a greenhouse in our gardens.

I must thus return to my initial question: “Why do we continue to propagate the nonsense of the ‘greenhouse’ analogy?” Unfortunately, I think we know the answer all too well.

But, more worryingly, if such fundamental scientific bunkum is allowed to flourish in science itself, in public reports, and in the media, surely we must begin to wonder what other rubbish is being tolerated and employed for propaganda purposes? What else is being ‘trapped’ by the emissions of bad science?

This is a Green gobbledygook too far.