Sunday, September 25, 2011

More on the Atmospheric Heat Pipe

Update: I found the issues with the spread sheet so I was able to clean up the chart. This time the invert values of the Stratosphere is in orange, so the trend lines are meaningful.

The Upper Atmosphere impacts are described in the link. There is a lot more going on than just radiative changes due to surface warming.

A while back I was puzzled over the temperature relationship between the mid Troposphere and the Stratosphere. Global warming has predicted that the troposphere should warm and the stratosphere cool. That is the general trend, but there are some oddities when you compare the monthly temperature values. This lead to the tropopause as a heat sink and the heat pipe analogy.

Heat pipes are a good way to remove sensible heat quickly. It involves a liquid to vapor phase change on one end, the cooling end and a vapor to liquid phase change on the other end, the heat sink. To work properly, the heat sink, or thermal reservoir used to pipe the heat to, must be much larger than the cooling load. The upper troposphere, tropopause especially, is an ideal thermal reservoir, because it can easily radiate heat to space except for a narrow band occupied by ozone. Ozone is warmed in the stratosphere by incoming ultraviolet radiation from the sun. It is also warmed by outgoing radiation in its absorption band. Increased CO2 should block a portion of that band reducing the warming due to outgoing radiation (small point in the co2 spectrum shared by ozone and water vapor). There is more to it than that, "In Ramaswamy (2001):

For carbon dioxide the main 15-um band is saturated over quite short distances. Hence the upwelling radiation reaching the lower stratosphere originates from the cold upper troposphere. When the CO2 concentration is increased, the increase in absorbed radiation is quite small and the effect of the increased emission dominates, leading to a cooling at all heights in the stratosphere." From Science of Doom.

Water in all its phases has a spectrum overlap with ozone. So variations in the emitted radiation by water in the upper troposphere can also impact ozone absorption. How significantly I am not sure, but it is possible that variations in the energy emitted to space by water can be causing the odd variations in stratospheric temperature.

Update: To better describe what I am calling the atmospheric heat pump, it is related to convection without precipitation. Warm moist air rising, cooling which condenses the water vapor and producing precipitation is well understood and included in all climate models. Clear sky thermals also move warm moist air higher where it cools the water vapor. Visible clouds may or may not form and clouds that do form may not precipitate, but that does not mean that heat is not being moved from warmer lower levels to colder upper layers where heat from water vapor can be radiated to either space or the atmosphere. Rising air will cause a lower pressure below it that will be replaced eventually by cooler air from above. If you have ever watched buzzards in a kettle, you have seen clear sky thermals.

All clear sky thermals would be "heat pipes" and these thermals from the surface are included in atmospheric models. They gain their energy, heat, from the surface mainly due to sunlight.

My theoretical Atmospheric Heat Pipe would be higher in the atmosphere, at the top of the atmospheric boundary layer, which is the lowest level of the atmosphere between the surface and roughly the base of the low level clouds. Water vapor in the atmosphere absorbs solar energy, not clouds, but water vapor absorbs approximately 10 percent and about half is re-radiated to space as infrared. These are approximations of averages. It is the change in the amount of the absorbed energy re-radiated that may impact climate.

Here is the crackpot part of the theory. During a solar minimum, there is a slight decrease in the overall solar energy spectrum. About 1 W/m^2 out of 1365 at the top of the atmosphere. At the surface, only one quarter of 70 percent of that change on average would be felt due to albedo, geometry and rotation. More of that change would be felt in the mid and upper troposphere. However, it is likely, that the near infrared portion of the solar spectrum varies little between solar minimum and maximum. This light energy imbalance could increase the efficiency of the atmospheric Heat Pump. Water in all its phases, is a strong absorber of infrared which is the power source of the theoretical Atmospheric Heat Pipe.

Sunday, September 18, 2011

Would the Earth Really Be 33 C colder Without Greenhouse Gases?

Thirty-three degrees C is the iconic value of the impact of greenhouse gases on Earth's climate. It is an estimate, probably not a bad estimate, but not carved in stone. CO2 does have a radiative impact on climate. Without it the world would be cooler, with more the world will be warmer, if all things stayed the same.

In the coming Ice age series, I am exploring the impact of water on climate, which is a much stronger and much more complicated Greenhouse gas. Most believe the addition CO2 in the atmosphere is over whelming the climate, but that same "most" don't feel that CO2 will cause a thermal runaway. The question to me has always been how much will CO2 do?

To estimate the impact of CO2, scientists calculate that with approximately 240 Watts/meter^2 at the top of the atmosphere (TOA) that the Earth's temperature would be 255 degrees Kelvin (K). So with the current temperature being 288K, greenhouse gases cause 33 degree K or C of warming. Based on this 33 degrees, the impact of CO2 can be calculated and about 1.2 degrees would be the impact of double CO2.

BUT, "If an ideal thermally conductive blackbody was the same distance from the Sun as the Earth is, it would have a temperature of about 5.3 °C. However, since the Earth reflects about 30%[6] (or 28%[7]) of the incoming sunlight, the planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) is about −18 or −19 °C,[8][9] about 33°C below the actual surface temperature of about 14 °C or 15 °C.[10] The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect.", From Wikipedia.

That reflection of about 30% is due to water vapor in the form of clouds in a large part. Liquid water which makes up most of our planet reflects only about 8 percent. Ice and snow reflect some and land some as well. Not including the reflective part of water vapor, can de-emphasize its relative impact versus CO2.

If Earth were a true blackbody, the temperature without a greenhouse gas atmosphere would be 5.3 C or 279.3 K or 9 degrees, not 33. If I estimate that water vapor accounts for 50 percent of the reflectivity, then the Earth without a greenhouse would be about 14 degrees cooler. Using the estimated 1.2 for a doubling of CO2 with this temperature, 0.51 degrees would be the estimated impact of doubled CO2.

There is nothing new here. With all things behaving properly, CO2 doubling will cause 1.2 C of warming. The difference between 1.2 and 0.51 just illustrates the uncertainty in the impact of clouds to an increase in CO2. The uncertainty with respect to clouds is nothing new either.

As if by magic, the IPCC estimated warming average is 3 degrees and the estimate based on observations is about 1.2 to 1.6 degrees. As I have mentioned before, that 3 degrees is not A estimate, but the average of two estimates. The first estimate was 2 degrees. So I think we should give a cigar to Manabe, the scientist that seems to have the better estimate.

If we take a look at the second estimate by Arrhenius, 1.6 (2.3 with water vapor) we have another estimate that is pretty close. The only fly in the ointment is Dr. James Hansen with his high estimate of 4 degrees. Well, he is nearing retirement.

Continuing: A while back I read an old post on Climate Audit, where Dr. James Annan tried to explain the estimate for climate sensitivity to a doubling of CO2.

"I noticed on your blog that you had asked for any clear reference providing a direct calculation that climate sensitivity is 3C (for a doubling of CO2). The simple answer is that there is no direct calculation to accurately prove this, which is why it remains one of the most important open questions in climate science.

We can get part of the way with simple direct calculations, though. Starting with the Stefan-Boltzmann equation,

S (1-a)/4 = s T_e^4

where S is the solar constant (1370 Wm^-2), a the planetary albedo (0.3), s (sigma) the S-B constant (5.67×10^-8) and T_e the effective emitting temperature, we can calculate T_e = 255K (from which we also get the canonical estimate of the greenhouse effect as 33C at the surface).

The change in outgoing radiation as a function of temperature is the derivative of the RHS with respect to temperature, giving 4s.T_e^3 = 3.76 . This is the extra Wm^-2 emitted per degree of warming, so if you are prepared to accept that we understand purely radiative transfer pretty well and thus the conventional value of 3.7Wm^-2 per doubling of CO2, that conveniently means a doubling of CO2 will result in a 1C warming at equilibrium, *if everything else in the atmosphere stays exactly the same*."

Before I estimated that clouds contribute about half the albedo so using Annan's equation we have 1370(1-.15)/w or 291.1 = s.T_e. So T_e = (291.1/(5.67x10^-8))^.25 = 268.9 K which is 13.9K greater than the 255K no greenhouse estimated temperature of the Earth. Instead of 33 C we could be 19.1 degrees warmer with a greenhouse atmosphere than without. Using the same derivative, the change in OUTGOING radiation required to increase the temperature 1 degree would be 5.59 Watts/meter^2 if I didn't screw up. Without going back through the derivation of the radiative impact of a doubling of CO2, I will assume 3.7 W/m^2 is correct. Then the temperature change for a doubling of CO2 would be 3.7/5.59 = 0.66 degrees C or K.

This does not mean that 5.59 W/m^2 is the radiative change in forcing required to increase the temperature one degree, just that water vapor may effect the initial estimate of 33 degrees. If the Earth was at an average temperature of 268.9 we would be in a snowball Earth, there would probably be less water vapor and more surface ice or snow so the impact of solid water with traces of water vapor could be an albedo of greater than 0.3. If the albedo of the Earth was .4, then T_e would be 205.5 and 3.4W/m^2 would equate to 1 degree change in surface temperature.

Note: This post is more of just a reminder for me. The accuracy of the ground based net infrared radiative measurements are not sufficient to confidently measure the temperature change for a small, less than one percent change in radiation. That may be changing.

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.

Friday, September 9, 2011

The Truth Generally Lies in the Middle

I get criticized for using this cliche on some other blogs. Well, it is a cliche because of a reason, more often than not it is correct. In the global warming debate I am more confident each day it is true. It is not always true though. The goal posts can change without someone gaming the system. Initially, the impact of CO2 enhanced global warming was a compromise. James Hansen predicted 4 degrees of warming, Syukuro Manabe predicted 2 degrees of warming. The range 2 to 4 degrees with the best estimate of 3 is the result of that compromise. Just add a half degree for uncertainty and you have the classic 1.5 to 4.5 range. At that time, the middle was the best truth, 3 degrees.

Times change. The classic 3 degrees was established in 1979, the dawn of the satellite era. It was also the at the beginning the modern warm period. Thirty years later we can see how things have played out.

The compromise is similar to the Monty Hall three door problem. With Hansen's estimate door number one, Manabe's estimate door number three and in the middle is the IPCC with door number two. Each had a possibility of being right, a 1/3 probability. Since the models thirty years later are leaning towards Manabe or IPCC, Hansen's door seems to have the booby prize. So where's the car?

If you picked door number two first, the is a little bit better chance it is behind door number three. If you picked door number three first, there is a little bit better chance it is behind door number two. Do you switch your door?

That is were the Global Warming debate is, door two or door three. So there is still a 50% chance the truth is in the middle, but if your first choice was the middle, you should think about changing.