If AGW is responsible for 1.6W/m^2 of retained energy how long will it take to raise soil temperature 1C?

Question

Assume soil is comprised of silica.

For reference, see http://answers.yahoo.com/question/?qid=20080804154304AAeIU9u

Answer 1

Solids/silica not having and average temperature, but a coefficient of -9x that of water. Would be about 35.166...7yrs.

Answer 2

I never studied soils, but I'll throw out a 25 year estimate based on this study:

http://www.springerlink.com/content/n836...

"Canadian Prairie provinces (mostly Alberta) show evidence of average warming at the ground surface (GST) of 2.1 K (standard deviation = 0.9 K) mostly in the second half of this century"

Edit: This study was using depths up to several hundred meters and your question doesn't specify how deep.

Answer 3

there isn't a good answer.

for one, it depends on how deep.

eg, starting at the surface, and with no depth at all, less than a day.

but that's not how it works.

heat conduction into the ground varies widely, and must be taken into consideration.

in addition, any specific temperature on earth is the balance between heat received, and heat radiated.

when the earth warms, it radiates more.

so to get an accurate answer, one needs to consider the increase in ration (heat loss) that 1 degree will cause.

as if that's not enough, one cannot ignore the oceans either.

as you'd know if you lived on the west coast, where temperatures along the coast pretty closely reflect the temperature of the water off the coast.

however, there is another way to look at this.

http://www.celsias.com/blog/images/globa...

the chart shows something like 0.8 degrees in 100 years.

but that's biased.

the CO2 levels have changed much more dramatically in the last 20-30-40 years.

so the 0.1 degree rise per decade we see in the last few decades would be far more representative.  

Answer 4

Well using a simple equation Q = mc(dT) where Q = heat, m = mass, dT = change in temp, c = specific heat...

specific heat for silica is 0.7 J/g-K which is pretty consistent with the standard specific heat of soil solids (0.725 J/g-K).

http://soil.scijournals.org/cgi/content/...

Mass density is somewhere around 2.2 g/cm^3.

You don't specify what depth, so let's just say we're talking about the upper foot of soil.  So that's a square meter area x 1/3 meter depth = 1/3 m^3 = 333,333 cm^3.  Thus the mass of this volume of soil is 2.2 * 333,333 = 733,333 g = m.

So Q = (733,333 g)*(0.7 J/g-K)*(1K) = 513,333 J = 513.3 kJ.  That's the energy required to increase the temperature of a square meter of surface soil (1 foot depth) 1°C.

So now we've got Power = 1.6 W = Energy/time = (513,333 J)/t. Solving for 't' I get 320,833 seconds, or 89 hours, or 3.7 days.

Of course, that's grossly oversimplified, because it doesn't take into account the distribution of the heat in the soil (i.e. transfer downward, how long that takes, etc.).  Basically I'm just calculating the time to heat up soil in an isolated, insolated box.  Just like with the ocean question, the depth complicates things, because the soil/water doesn't warm up uniformly at all depths (as Noah assumed), nor is all the heat isolated in the upper foot (as I assumed).  So the correct answer is somewhere inbetween.

And regardless, to correctly assess the impact of radiative forcing on the surface temperature, we should be doing this calculation for air, not soil.  That's what the surface stations measure (air temperature).