by DR. TIM BALL on AUGUST 12, 2013
“It occurred to me…” that eventually all those people texting will eventually end up writing Shakespeare’s plays.
Analogies are a valuable teaching device converting everything from ideas to objects into supposedly more recognizable forms. They includes biblical parables, Aesop’s Fables, hardware models, toys, computer models and even mathematical formulae. However, something is always lost in translation. How many school science projects fail to miniaturize the flow characteristics of ice?
The greenhouse/atmosphere analogy is much more problematic because most parts don’t work in the same way. Its value was political because people associate a greenhouse, or hothouse, with increased heat. But that’s appropriate because the hypothesis and attempts at proof that human CO2 was causing warming are political.
Another deceptive value is that few know how a greenhouse works and even fewer the atmosphere. Indeed, nobody knows how the atmosphere works. If they did, weather and climate forecasts would work.
The basic idea of a greenhouse is that sunlight or shortwave (SW) energy passes through the glass and heats surfaces. The surfaces radiate that heat as longwave (LW) energy or sensible heat (heat you can feel). LW cannot pass through the glass, so is trapped and raises the temperature in the greenhouse; the glass acts like a one-way valve. A greenhouse is a closed system because the heat cannot escape unless artificially changed by opening vents or blocking sunlight. The glass supposedly represents the entire atmosphere. It also blocks 100 percent of the ultraviolet (UV) portion of the sunlight.
The atmosphere is an open system, with heat energy always escaping to space. Unlike the glass it absorbs 95% of the UV in the creation of ozone. This sounds insignificant, but one scientist argues variation in the 5 percent is the cause of warming.
CFCs are already known to deplete ozone, but in-depth statistical analysis now shows that CFCs are also the key driver in global climate change, rather than carbon dioxide (CO2) emissions.
In the greenhouse and in the atmosphere energy is partly transferred from the heated surfaces through collision between air molecules (conduction). However, in the atmosphere a large portion of that heat is transported vertically by rising air currents (convection), and also horizontally by advection or commonly wind. There are no winds in a greenhouse.
A major part of the energy striking the Earth’s surface causes evaporation. It increases water molecule speed so they escape the surface changing from liquid (water) to gas (water vapor). Heat is not lost (latent) but transported with the air and released when condensation occurs. This released heat warms the atmosphere, explaining why temperatures rise when it rains. This does not occur in a greenhouse.
The greenhouse glass blocks all LW and supposedly represents three atmospheric gases, water vapour, carbon dioxide and methane, known as greenhouse gases (GHG). They do not block all sensible heat and only temporarily delay escape to space. There are no analogous greenhouse components for the other gases or atmospheric factors. For example, dust particles significantly reduce SW and LW in the atmosphere.
GHGs don’t raise temperature like glass in a greenhouse. They modify atmospheric temperatures by reducing highs and increasing lows. In all weather and climate considerations water modifies temperature. Desert day – night temperature range is the highest anywhere due to lack of water vapour; not CO2. Commercial greenhouse operators raise CO2 levels to 1200 ppm, three times atmospheric levels. It doesn’t raise the temperature, but increases crop yields four times.
Heat reduction in a greenhouse requires a physical change with a vent to let LW escape or a screen to block SW entering. Clouds are nature’s screen. However, they can block SW and LW, such that we have little idea how clouds work to modify temperatures. As the National Science Foundation says, clouds are the wild card of climate change. In the 2001 IPCC Report it says,
“In response to any climate perturbation the response of cloudiness thereby introduces feedbacks whose sign and amplitude are largely unknown.”It is like putting shades in a greenhouse and not knowing what they are going to do. So we have a model of the atmosphere that doesn’t know how clouds work but is the sole basis for climate predictions of global warming.
The Earth’s atmosphere is not like a greenhouse. It is a completely inappropriate analogy sadly equalled only by the false claim that climate models are an analogy of global climate.
Related: Also published today, "The Greenhouse Effect" from KE Research, Germany