[intelex22 (OP)]

Before I begin, let me first assure you that I'm not a troll, I don't work for any energy interests, and I generally agree with the proscribed outcomes of CO2 as "the cause" of global warming.  But as a scientist who works with computational models, I know that calibration parameters drive much of the outcome.  For those looking toward advanced degrees in climatology, I think this could form the basis of a very interesting thesis.

This is a continuation/rehashing of a thread I came across and was enjoying from earlier:  newbielink:http://www.thenakedscientists.com/forum/index.php?topic=39128.0 [nonactive]
(It motivated me to offer my own, independent observations)

I have discussed alternate driving factors in global warming with a few researchers and climatologists, including former Oregon state climatologist George Taylor and Eric Steig at the University of Washington.  It appears that the answers are far from clear and detailed assessment hasn't been completed to rule this out.  I think it should be evaluated.

Relax your mind... and consider:

Theory -
1) Recent "global warming" began around 1910. 
2) Warming was temporarily halted/reversed due to above ground nuclear blasts (AGNB) from 1945 to 1975.
3) Weakening of Earth's magnetic field is likely the driver in this change.
4) The importance of CO2 as a greenhouse gas is overstated.  Water vapor may be playing a more substantial role.

Evidence -
Global Cooling - The first time I ran across an average global temperature plot with a 5-year rolling average, I noticed what had been previously described and discredited in the 1970's as "global cooling." It seemed there was no good reason for it, and it bounced around in the back of my mind for a couple years. 

As a component of North Korea's nuclear testing, I ran across an interesting data set - the total number of AGNB's per year and by country (online from a non-proliferation group).  Within the data set, I noticed a pattern and compiled a plot of totals tests per year.  Then I looked up that temperature plot again and overlaid the image I made.  Keep in mind that the plot doesn't reflect detonation yield or location.  (Please pardon the slightly ghetto look as I didn't have the numerical raw data sets for temperature/etc. to truly plot these together.

There are two components which may have been influential. 
A) Direct addition of particulate into the high atmosphere. 
B) The introduction of substantial sulfur mass into the atmosphere.

Instead of a "nuclear winter," I wondered if we induced a "nuclear fall" with the detonation of up to 120 AGNBs around the world during this period - tossing dust, debris, oxides, particulate, smoke, etc. into the upper atmosphere.  Add on top of that, nuclear testing in atolls vaporizes sea water, which contains approximately 900 parts per million of sulfur - a well understood global coolant commonly associated with volcanic eruptions.  If one of these blasts vaporized a billion gallons of seawater, that would be over 10 million kilograms of sulfate directly added to high levels of the atmosphere - each time.  The Partial Test Ban Treaty then took further testing underground for the US and the Soviets after 1963, and the last AGNB was conducted by China in 1980.

Warming Alternatives -
AA) The Earth's magnetic field reduces the number and mass of solar particles (from the solar wind) that interact with our atmosphere by a mechanism known as the Lorentz force.  Indeed we have only begun assessing the complexities of this process directly with the ESA's Cluster mission.  Stronger pulses in the slow solar wind (associated with the solar cycle) result in Kelvin-Helmholtz waves at the magnetopause, allowing waves of particles to accumulate within the Van Allen radiation belt.  Some of these particles interact and penetrate the ionosphere and upper atmosphere with enough energy to heat the molecules, generating plasma (auroras).

We now know that the polarity reversal of the Earth's magnetic field occurs (on average) every 200,000 years.  The last one was approximately 780,000 years ago (long overdue).  Detailed nautical records over the last 300 years have detected various "anomalies" in the direction and strength of the magnetic field at the surface.  In some areas of the planet, such as the south Atlantic, localized polarity reversals have been documented.  It is widely accepted that we are in the midst of a polarity reversal, during which time the structure of the magnetic field will become more chaotic, possibly changing as much as 6 degrees per day in some areas (as has been noted in geological records).

The thread noted above had the first plot I have seen where ice core temperatures were co-plotted with the magnetic field strength.  And I think that is a good place to start and it should be explored further.  Much of what I have seen in public discussion of temperature trending doesn't extend back to the last polarity reversal.  Despite the hard work and great science behind analyzing 100,000 year old ice cores - if it doesn't date back to the last polarity reversal, the data set is substantially flawed and may not reveal a single, complete data cycle.

Conclusion - I suspect that it isn't solar output, but a subtle difference in the amount of solar radiation making it to the atmosphere that is the root cause of climate temperature increases that began in 1910.  Why 1910 appears to be a tipping point, I'm not sure.  But when you consider that the 5-year average temperature delta (slope) is essentially the same from 1910 to 1945 as from 1975 to 2010, it become apparent that the trend in CO2 is probably not main culprit.

If there is a human component to global warming, I suspect that our removal of billions of cubic feet of water from ancient underground aquifers for irrigation could be playing some role in trapping heat near the surface. we know that the molecular influence of water has a greater impact than CO2 and the concentration of water is much higher than CO2.  CO2 mirrors food consumption and methane production from animals with rumin (like cows).  As the population grows, more water will be extracted to grow more food, more CO2 will be used due to the availability of energy dense hydrocarbons, and more beef production will produce more methane and even more CO2. 

So, I see a plausible scenario where CO2 is actually more a proxy than cause for post-1975 warming.  Before that, the correlation is dubious.

[alancalverd]

Sound basic thinking regarding water, but I don't think human activity has altered it much: we cut down a few forests and replace them with grass, but 90% of the earth's surface is unaffected by human activity - 75% of it is ocean! - and the area of agricultural land hasn't increased greatly in the last 50 years. I think the water cycle is inherently chaotic and catastrophic - the ice core record shows extremely rapid temperature rises with very slow decreases, which suggests a nonlinear feedback mechanism (water fits the bill) or a catastrophic trigger (magnetic field reversal is catastrophic on this timescale but the trigger effect needs more proof).

Full marks for spotting the CO2 exhalations of farm animals. This was the subject of my paper (Physics World, July 2005) that caused a lot of interest among the vegetarian community and even became UN and government policy. What interests me is that it accounts for 20  - 25% of anthropogenic CO2 and is entirely dispensible (we could actually feed more people on the same land if we stopped breeding cattle) therefore a potential experimental variable.

The magnetic field idea is interesting but at a first glance there seem to be as many anticorrelations as correlations in the graph you referred to. Nevertheless it is important source material since it is objective and unambiguous, so worth a more careful computation.

Nuclear testing gives us a time correlation but

If the quantity of water that is condensed in and subsequently precipitated from a cloud is known, then the total energy of a thunderstorm can be calculated. In an average thunderstorm, the energy released amounts to about 10,000,000 kilowatt-hours (3.6×1013 joule), which is equivalent to a 20-kiloton nuclear warhead. A large, severe thunderstorm might be 10 to 100 times more energetic.

and there are about 1000 thunderstorms taking place all the time. The quantity of solid material sucked up in  a megaton airburst doesn't compare with a decent volcanic eruption: it's just easier to identify because it contains short-lived isotopes.   

But if we go back to the ice cores, it is clear that CO2 follows temperature, so it is the thermometer, not the thermostat.

Power to your typing finger!