Memories of the 28th Century

I was told that I should write on Climate Change again. I complained that I already had done so enough, but I couldn’t think of anything better to write about, so I looked into the periodicity of climate change. It is a very interesting subject, and there is more to be done with it, but there isn’t enough data for everything to be put together in a neat, compact essay, and the scientists have the same problem. There are several types of variation in solar heating of the Earth; some are effects of the Earth’s orbit, while others are matters of the Sun. These three cycles are called Milankovitch cycles.

Over time the Earth’s orbit becomes at time rounder and at other times more eccentric (more elongated). The elongation results in greater differences in temperatures from season to season; right now the orbit is relatively round.

Then there is axial tilt (obliquity). Now the Earth’s axis tilts about 23.5 degrees from vertical. Over time the tilt has been as little as 22.1 degree. The difference isn’t huge, but less axial tilt leads to colder temperatures near the poles, because lees sunlight reaches that region during Summer.

Then we have precession, the angle of the tilt with respect to the place in orbit. At present the tilts most away from the Sun near the Winter Solstice, when the Earth is closer to the Sun. This leads to less heating of the major landmasses.

We all know about the sunspot cycle. Sunspots go from maximum to minimum in an eleven year cycle. Temperatures tend to be higher during sunspot maxima.

There are several other cycles of varying length but of less well-known origins. http://en.wikipedia.org/wiki/Solar_variation . .


Cycle length Cycle name_____Last positive________Next "warming"
232__________--?-- ________AD 1922 (cool)_____AD 2038
208__________Suess________AD 1898 (cool)____AD 2210
88___________Gleisberg_____AD 1986 (cool)_____AD 2030


Plus the 2,300 years: Hallstatt cycle, the 6000 years (Xapsos and Burke, 2009), and a few others. And some work has been done that indicated that there were harmonic combination of different cycles. There isn’t any sign that anyone has looked into how one cycle affects another, but that is something that probably would happen based on the nature of the different cycles. I couldn’t find anything that indicated a larger cycle in sunspots, something that would account for the various minima and maxima, but there probably is a super cycle, or something else is causing the variations.

I think the total is at least seven cycles. I was going to chart some together, but seven would be too messy to be useful. In addition,
‘The sensitivity of climate to cyclical variations in solar forcing will be higher for longer cycles due to the thermal inertia of the oceans, which acts to damp high frequencies. Using a phenomenological approach, Scafetta and West (2005) found that the climate is 1.5 times as sensitive to 22-year cyclical forcing relative to 11-year cyclical forcing, and that the thermal inertia of the oceans induces a lag of approximately 2.2 (± 2) years in cyclic climate response in the temperature data.[35]” from http://en.wikipedia.org/wiki/Solar_variation


It is quite clear that none of the mechanism that have been proposed for causing climate change are adequate explanations, but the observations cover only a rather short time with any reliability; although we have descriptions of climatic conditions tell a good story for a long time, and we can infer climatic conditions from agricultural outputs for a considerably longer period. Unfortunately, none of the observations match the known cycles; although there is some correspondence with harmonics.
“Perry and Hsu (2000) proposed a simple model based on emulating harmonics by multiplying the basic 11-year cycle by powers of 2, which produced results similar to Holocene behavior. Extrapolation suggests a gradual cooling during the next few centuries with intermittent minor warm-ups and a return to near Little Ice Age conditions within the next 500 years. This cool period then may be followed approximately 1,500 years from now by a return to altithermal conditions similar to the previous Holocene Maximum. [36]”
Even if they did an excellent job we will have to wait to see.

I was hoping that there would be some relationship between sunspots and longer range patterns, but there isn’t. Apparently the relationship is coincidental.
Solar activity events and approximate dates
Event ___________________________Start__End
Homeric minimum[29] ____________950BC_800BC
Oort minimum____________________1040__1080
Medieval maximum________________1100__1250
Wolf minimum____________________1280__1350
Spörer Minimum _________________1450__1550
Maunder Minimum________________1645__1715
Dalton Minimum _________________1790___1820
Modern Maximum_________________1900__present


Looking at the various cycles, it becomes clear that there probably will not be an especially warm period or an ice age in the immediate future, even though several cycles are pointed toward the ice age. Combining that with the fact that the present level of temperatures in significantly lower than the Medieval Warm Period, it appears that we will continue to have rather normal climate with reason for *****ing about the cold of Winter and grousing at the heat of Summer. If you are interested in doing something about that, then you will be interested in my next post, which will discuss triggering a new ice age (it isn’t difficult).

This is a subject that becomes ever more interesting the more I learn about it, but it also becomes ever clearer that today still isn't up to the level of the Medieval Warm Period.



Further reading:

http://en.wikipedia.org/wiki/Solar_variation

Sunspots
http://earthguide.ucsd.edu/virtualmu...ge2/06_3.shtml
Unstoppable solar cycles
http://heartland.org/policy-document...global-warming
Variation in eccentricity
http://en.wikipedia.org/wiki/Milankovitch_cycles

Jupiter and Venus Effect on Earth's Climate
http://cosmoquest.org/forum/showthre...arth-s-Climate

http://www.indiana.edu/~geol105/imag...lankovitch.htm

http://en.wikipedia.org/wiki/Sunspot_cycle