What Causes Ice Ages?

  • #26
4,465
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problem though is that the interpretation of proxies is almost a comedy of errors.
 
  • #27
What Causes Abrupt Planetary Temperature Changes?

The paleoclimatic data shows that there have been regular periodic abrupt changes in planetary temperature. It appears that the short term increases and drops in planetary temperature are due to changes in the solar cycle (Increases similar to the 20th century warming which it is hypothesized was primarily caused by high solar activity and a drop in temperature due to a solar cycle change to a Maunder Minimum or to a Super Maunder Minimum). It appears that the long term drops in planetary temperature are due to abrupt and long term drops in the geomagnetic field.

Both the solar changes and geomagnetic field changes modulate the amount of planetary cloud cover. As low level clouds reflect short and long wave radiation back into space, an increase in low level cloud cover cools the planet and a decrease warms the planet.

Is there data that supports the hypothesis that cloud levels are modulated by changes in the solar cycle and geomagnetic field changes?

Attached is a link to Enric Palle’s (2003) paper that provides data and analysis that supports at a 99.5% confidence level that low level planetary cloud cover, tracks changes in Galactic Cosmic Rays (GCR) 1983 to 1993. For the period 1993 to 2001 planetary cloud cover continues to track GCR changes except for a persistent reduction in cloud cover. The reduction in cloud cover is believed to be due to the “electroscavenging” process.

See copy of Palle's satellite paper. (See figure 2. Note low level clouds are reduced by minus 0.065% per year, starting in about 1993.)

http://solar.njit.edu/preprints/palle1264.pdf

Comment: Planetary cloud cover is believed to modulated by two processes: 1)Changes in the number and strength of the Galactic Cosmic Rays that strike the earth's atmosphere and create cloud forming ions (The geomagnetic and Solar large scale magnetic fields, partially block GCR) and 2)Changes to the earth's global electric circuit which removes cloud forming ions. Data and analysis indicates that changes to the global electric circuit are caused by high speed solar winds, that are caused by solar coronal holes that started to appear near the solar equator 1993 and on.) The next comment provides a link to Yu & Tinsley's paper that describes how both processes affect cloud formation and physical properties.

Some climatologists stated that the satellite analysis of cloud cover could be incorrect. (There was a paper published that ridiculed Svensmark’s paper which had analyzed the satellite data.) Palle's paper re-examined the satellite data, using a different analytical technique than Svensmark had used, which addressed others complaints concerning Svensmark's paper. Palle’s analysis of the satellite data confirmed Svensmark’s original finding. As climatologists were still skeptical, Palle measured the change in planetary cloud cover using a completely different observation technique.

Attached below is a link to a second Palle paper that provides data from observing the shine of the earth on the moon, to measure planetary albedo. The earthshine data, confirms that planetary cloud cover tracks GCR and that planetary cloud cover was reduced in the 1993 to 2001 period, which completely supports the satellite data and analysis.

http://solar.njit.edu/preprints/palle1266.pdf

Palle’s earthshine analysis found that the 1994 to 2001 reduction in cloud cover warmed the planet by 7.5 W/m2 +/- 2.4 W/m2 which is three times greater than the total estimated greenhouse gas estimated warming for the 20th century. (Note the 20th century very high solar activity is over. Will the planet cool? If so, how much and how quickly?)

From Palle's earthshine data paper:

Our observations of the earthshine take the ratio of the earthshine to moonshine, so they are insensitive variations of the solar irradiance. The 5 +/-2% change in our observed reflectance translates to …. Solar and terrestrial changes are in phase and contribute to a greater power going into the climate system at activity maximum. However, the effect of the albedo is more than an order of magnitude greater. Our simulations suggest a surface average forcing at the top of the atmosphere, coming only from changes in the albedo from 1994/1995 to 1999/2001, of 2.7 +/- 1.4 W/m2 Pall e et al., 2003), while observations give 7.5 +/-2.4 W/m2. The Intergovernmental Panel on Climate Change (IPCC, 1995) argues for a comparably sized 2.4 W/m2 increase in forcing, which is attributed to greenhouse gas forcing since 1850.

Still, whether the Earth’s reflectance varies with the solar cycle is a matter of controversy, but regardless of its origin, if it were real, such a change in the net sunlight reaching the Earth would be very significant for the climate system.
 
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  • #28
Periodic Planetary Temperature Drop?

Evidence that both Northern and Southern hemispheres cool in response to periodic solar changes?

This paper provides data that shows that the well known and discussed periodic cooling events in the Northern Hemisphere appear to have occurred concurrently with Southern Hemisphere cooling events. Both the Northern and Southern Hemisphere periodic cooling events appear to coincide with solar activity minimums.

"Solar modulation of Little Ice Age climate in the tropical Andes"

http://www.pnas.org/cgi/reprint/0603118103v1.pdf

Quoted from the above paper.

The underlying causes of late-Holocene climate variability in the tropics are incompletely understood. Here we report a 1,500-year reconstruction of climate history and glaciation in the Venezuelan Andes using lake sediments. Four glacial advances occurred between anno Domini (A.D.) 1250 and 1810, coincident with solar activity minima. Temperature declines of approx. 3.2 +/- 1.4°C and precipitation increases of approx. 20% are required to produce the observed glacial responses.
 

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