Thursday, September 15, 2011

The Coming Ice Age? Part V It's the Sun Stupid

It's the sun stupid, has been used by skeptics of global warming for a long time. There is a fair correlation of solar cycles and temperature. Not great. Fair. Since we now know that the actual change in solar energy during its cycles is not that much, it is have to show that there is a mechanism linked to solar that can make large changes in climate. Somewhere between a tenth of a degree and two tenths of a degree is all that the sun can muster climate change wise. So how can it be the sun, stupid?

Glad ya asked. Timing and location is the answer. The short ~11 year solar cycles don't seem to do much, as expected. We haven't seen a longer cycle with our modern satellite eyes, so I am allowed to put on my Carnack turbine and foresee the future, by looking at the past.

The little ice age was in the past. it was a time when it was colder in the northern hemisphere and it just happened to coincide with a prolonged sun spot minimum, the Maunder minimum. During the Maunder minimum the solar output was less, about 1 to 2 Watts per meter squared for a prolonged period of time, about 22 years or two solar cycles were very calm with one before and one after probably smaller than normal.

Above is a reconstruction of the sun spot cycles I found on Wikipedia. The only reason I don't say there were four dead low cycles is because the accuracy back then may not have been all that great. Based on current solar energy changes, during the Maunder minimum the energy from the sun was about 1 W/m^2 less than normal. There is still a good bit of debate of that number, but that's the one I am going to use right now.

One W/m^2 is not much. Average over the whole Earth and allowing for reflection and all that it would only be about 0.25 W/m^2 at the surface. So little that most scientists blow it off and others look to explain why it should be more. But it may not have to be more.

Where that change matters is near the equator and over the ocean. Since there is more ocean than land south of the equator, that is where it would matter most. In this area, the change in solar irradiation would be closer to the full 1 W/m^2. I know the sun rises and sets and all that, but most of the heat the oceans gain is near the noon. Most of that heat is in the first few feet where the longer wavelengths of light are absorbed, but a fair amount, roughly 10% of the solar penetrates the deeper water and is locked in for a longer time period. It takes a long time for the water at depth to warm and just as long to loss that warmth. Slow motion in the ocean.

One of the fairly new revelations in he solar physics community is that the short wave lengths of solar radiation tend to change more with the solar cycles than once thought. Ultraviolet radiation may change by 6 percent while the overall change is only about 0.1 percent. A 6 percent change is a small percentage of the total radiation is still pretty small, but it is large with respect to the deep ocean energy balance. UV along with its closer wave lengths violet, blue and green, penetrate to over 100 feet in the ocean. UV is a little weird, it tends to be absorbed better and shallower if there are micro-organisms. That throws a little wrinkle in the logic, but not too much.

During high solar cycles, there is more energy absorbed by the oceans. During low or weak solar cycles less, so the energy absorbed in the deep southern ocean may vary by 6 W/m^2 per day. The W/m^2 is in seconds, so I should do the math, but let's just stick with that number as a reference. Now 6 W/m^2 is nothing compared to 1000 W/m^2 on a clear day, but at the depths, 6 W/m^2 compared to 100 W/m^2 is significant. That would give you an idea of the change in energy absorbed below 100 feet in the southern oceans between a solar maximum and a solar minimum. Still not enough to impress most folks, but enough to turn a few heads.

That is about all the change in the solar radiation. Not enough to explain things but a start. Oh, what would happen if say, cloud patterns in this area of the ocean changed? Looks like the topic of my next post.

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