Tuesday, May 29th 2012, 4:44 AM EDT
Nicola Scafetta, is a scientist at Duke University and at the Active Cavity Radiometer Solar Irradiance Monitor Lab, which is associated with the NASA Jet Propulsion Laboratory in California. He claims "At least 60% of the warming of the Earth observed since 1970 appears to be induced by natural cycles which are present in the solar system.” As his theory is controversial we asked him to outline it. For the near future he predicts a stabilisation of global temperature or cooling until 2030-2040.
Q. What is your solar system cycles theory?
The theory is very simple in words. The solar system is characterized by a set of specific gravitational oscillations due to the fact that the planets are moving around the sun. Everything in the solar system tends to synchronize to these frequencies beginning with the sun itself. The oscillating sun then causes equivalent cycles in the climate system. Also the moon acts on the climate system with its own harmonics. In conclusion we have a climate system that is mostly made of a set of complex cycles that mirror astronomical cycles. Consequently it is possible to use these harmonics to both approximately hindcast and forecast the harmonic component of the climate, at least on a global scale. This theory is supported by strong empirical evidences using the available solar and climatic data.
The closest analogy is given by the harmonic model currently used to predict ocean tides.
Q. What is the physical mechanism?
There are three major mechanisms acting together: gravity, nuclear fusion - luminosity production, magnetism.
1) The planets act on the sun mostly via gravitational tidal forcings that are characterized by the astronomical harmonics in the same way that the tides on the Earth are regulated by lunar/solar gravitational harmonics.
2) The sun is in a state of almost perfect balance between gravitational forces and nuclear fusion luminosity production. This balance is very sensitive to gravitational or luminosity changes. If, for example, gravitational forces make some additional work (relative to a given average) on the sun, the sun responds by increasing its luminosity production to restore the balance, and vice-versa. The planetary tides slightly modulate the gravitational work balance inside the sun, and the sun responds by modulating its luminosity production. Because the luminosity production is energetically around 1,000,000 times the gravitational work released into the star, the solar core should work as a great amplifier of the planetary gravitational tidal energy. Thus, solar luminosity and all dynamical solar processes end up oscillating with a set of frequencies related to the planetary frequencies. This is the theory I propose in my last published paper, just last week.
3) The oscillating sun induces equivalent magnetic oscillations in the heliosphere. Magnetic oscillations have numerous effects: they modulate the incoming cosmic ray flux and modulate other electric currents in the heliosphere, that is, they regulate the space weather which is mostly made of electric phenomena. These phenomena occur together with the luminosity oscillations.
The Earth system is very sensitive to these electric changes because they cause ionization of the upper atmosphere and regulate cloud formation. Thus, the cloud formation will approximately follow the astronomical harmonics and make the albedo oscillate by about 1-3% . An oscillating albedo causes oscillations in the amount of light reaching the surface of the Earth, which is what causes the oscillations observed in the surface temperature.
Of course at the moment not all single physical mechanisms are understood, quantified or modeled.
Point 1 has can be easily quantified
Point 2 has been quantified, at least I made a proposal, but a full model also needs empirical modeling because solar physics is not so advanced.
Point 3 needs the understanding of how clouds form in details and the relation with cosmic ray etc. that is still under study. The modeling can be empirically done.
Q. How are your forecasts comparing with global temperatures?
The astronomical harmonic temperature model has been tested in its hindcast/forecast capabilities and performs quite well.
For example I calibrated the model in the period 1850-1950 and was able to reproduce all decadal multidecadal variation observed from 1950 to 2012, and vice versa. A full model that also included a possible anthropogenic component has been calibrated from 1970 to 2000 and was able to accurately forecast the temperature trend from 2000 to 2012.
About the solar harmonic model: it has been constructed by using physical information obtained in the period 1750-2010 and was able to hindcast all major solar and climatic variability observed during the Holocene (12,000 years). For example the model approximately hindcast the little ice age, medieval warm period, Dark Age cold period, roman warm period etc. The model reconstruct all secular scale oscillations observed in temperature and solar records for 2000 years at least: these include the Maunder minimum, Dalton minimum and other grand solar minima. Of course the model predicts the current warm period and a 60-year major modulation observed in the temperature since 1850. Thus the model may give some good idea about the future too. The sun is entering in a gran minimum that will reach the lowest level around in the 2030s and reach a new maximum in 2060s, the temperature will be partially regulated by this cycle.
Q. What is the reaction from other scientists?
The theory that I am proposing is relatively new and somehow revolutionary. Four major papers have been just published since January 2012. A real reaction can be measured only in the future.
The few scientists that have spent sufficient time in really studying my paper with an open mind were quite impressed and interested.
Unfortunately, the mainstream climate community and also the solar community is very closed because of their almost religious assumption that the science is settled and/or that climate (or the sun) is regulated by internal mechanisms alone.
So, it is easy for many to simply dismiss what I say without really understanding it. But, as I said major papers have been just published. So, I do not have really significant reaction yet.
However, the fact is that I can hindcast major properties observed in climate and solar records for decades, centuries and millennia, as my papers demonstrate while the mainstream climate community cannot do it. My models overcome any IPCC GCM for accuracy that is also demonstrated in one of my recent peer review publications just published.
Evidently, there is the need wait some time for a full acknowledgment of the entire scientific community.
Q. Is a rational debate possible?
Yes, but there is the need to study the results that I am finding well. A rational debate requires the willingness to understand what the other person would like to say and how he is making the arguments: understanding what are his findings and so on. All this is time consuming, of curse.
The issues are evidently complex, many physical details are of course still unknown and what is known needs to be understood in the way it can be understood, not just in the way one wishes to understand it.
A rational debate needs to be based on data analysis and their careful study, that is, people need to look at the data and at the results "carefully". People should not have the pretense that everything should have been clearly understood and explained already: we are talking about frontier science where it is normal to have open issues, etc.
Indeed, it is not difficult to understand the concept of "cycle" and if well presented the message is indeed quite simple and understandable.
By the way, people have always understood climate as partially/mostly influenced by astronomical cycles since antiquity up to the 20th century. From Ptolemy to Kepler, that was how climate change had to be understood. So, the theory I propose continues a long tradition, although right now it is an almost forgotten tradition.
Further details: http://www.duke.edu/~ns2002/#astronomical_model