Some background -
Willis Eschenbach had a guest posting over at WUWT in which he claimed that LWIR could heat Earth’s oceans. Myself and several others on the thread contended that this LWIR was likely to be stopped by the evaporative skin layer and would not slow the exit of heat from the oceans. Numerous requests for empirical evidence to support Willis’s claim only resulted in one inapplicable study used by the “Hockey Team” to support such claims. After several hundred comments without empirical evidence being offered, I gave up reading and designed and conducted an empirical experiment that shows that any effect of backscattered LWIR on the cooling rate of water would be negligible.
What follows is an edited version of the experiment design and results as posted on the WUWT thread. I would encourage others to conduct similar experiments to check my results. The equipment required is not overly expensive and the results can be observed in minutes. The results appear to show the measurable difference between reflecting LWIR back to warm water when it is free to evaporatively cool and when it can only cool through conduction and radiation.
What is required -
- Two identical probe type digital thermometers with 0.1 degree resolution
- Two identical insulated water containers. I used rectangular 200ml Tupperware style containers, insulated on their base and sides with foil and Styrofoam. I cut away the clip on rim from each lid to create a frame to clip down cling film for Test B of the experiment.
- One IR reflector. I used an A4 sheet of 10mm Styrofoam with aluminium foil attached with spray adhesive.
- One IR window. I built an A4 size “picture frame” of 10mm square balsa wood strips and stretched cling film over it.
- One 1 litre measuring jug
- Two small identical computer fans. I used Suron 50mm centrifugal blowers powered by a 6v gel cell battery
- Extra cling film
- Optional extras – kitchen timer, an A4 ”dark cool sky” panel of matt black aluminium with peltier cooling, glamorous lab assistant of choice.
What to do -
- Position probe thermometers in identical positions in both water containers. I placed the tips 10mm below the water line by drilling force fit holes in the sides of the containers.
- Position IR reflector and IR window 50mm above either water container. You may need to build two Styrofoam side walls, but air must be free to move over the surface of the water. (The use of the IR window is to ensure that air flow is similar over each water container.)
- Position the computer fans to blow across the water surface of each container, but do not turn on.
- Fill jug with warm water, stir, then fill each water container from the bucket. I used water around 40C as the ceiling was around 18C not a 3k sky.
- When and equal amount of water is in each container, turn on the computer fans.
- Observe the temperature change over time for each tank. Less than half an hour is required for such a small amount of water. You should observe that both tanks cool a the same rate (TEST A).
- Now the important bit – Repeat the experiment, but this time lay a small sheet of cling wrap on the surface of the water in each water tank. This allows cooling through radiation and conduction but prevents evaporation. You do not need the computer fans on in this test. You should be able to observe that while both containers cool slower than before, water under the IR reflector cools slowest (TEST B).
In TEST A the water cools more quickly, however the two water containers temperatures remain very close to each other over time. This indicates that backscattered LWIR has a very limited effect on the rate of cooling for water when it is free to evaporatively cool.
In TEST B both water containers cool more slowly than test A, but a divergence in temperature between the two water containers is readily detectable. The container under the foil sky cools more slowly than that under the cling wrap sky. This indicates that backscattered LWIR from a warm material can slow the rate at which that material cools, if radiation and conduction are the only methods for cooling.
Test A represents the evaporative cooling conditions in the real oceans. Test B represents how the climate scientists have modelled the oceans with regard to backscattered LWIR. From what I have observed, backscattered LWIR can slow the rate at which substances cool. However in the case of liquid water that is free to cool evaporatively this effect is dramatically reduced. It would appear that including the oceans in the percentage of Earth’s surface that could be affected by backscattered LWIR may be a serious error. Earth’s oceans cover 71% of the planets surface. If backscattered LWIR cannot measurably affect liquid water, then CO2 cannot cause dangerous or catastrophic global warming.
I have conducted further tests using a “cold sky” panel cooled with ice water over the top of the cling film IR window. While the temperature divergence in the evaporation restricted test B does not appear faster, it does appear to diverge for longer.
I would encourage others to conduct similar empirical experiments and share their observations. I would be interested in comments in further experimental design, or empirical evidence related to the LWIR question.
Typical TEST A
|Time||Cling Wrap Screen||Foil screen|
Typical TEST B
|Time||Cling Wrap Screen||Foil screen|