All these discussions about coal reserves are completely academic. The limiting factor is not the coal reserve (resource side) but the absorption capacity of the atmosphere for CO2 (sink side). In fact, our atmosphere is already overflowing with CO2. Carbon dioxide concentrations are now much higher than they were in the warmest interglacial period during the last 500 k years when sea levels were several metres higher than now. So we are clearly in overshoot mode already.

Lessons from the Arctic summer sea ice melt in 2007:

A doubling of climate sensitivity would mean we passed the widely accepted 2°C threshold of
"dangerous anthropogenic interference" with the climate four decades ago, and would require us to
find the means to engineer a rapid drawdown of current atmospheric greenhouse gas.

If, for example, instead we were to apply a 0.5°C (or lower) precautionary warming cap, it would be
necessary for the level of target atmospheric greenhouse gases at equilibrium not exceed about 320 ppm CO2e, a point we passed more than half a century ago.

www.carbonequity.info/PDFs/Arctic.pdf

NASA climatologist James Hansen is working on a new paper:

Remember This: 350 Parts Per Million
By Bill McKibben
http://www.washingtonpost.com/wp-dyn/content/article/2007/12/27/AR200712...

We are now at 383 ppm and rising.

The unusual warmth in 2007 is noteworthy because it occurs at a time when solar irradiance is at a minimum and the equatorial Pacific Ocean is in the cool phase of its natural El Nino – La Nina cycle.

Discussion of 2007 GISS global temperature analysis is posted at Solar and Southern Oscillations
http://www.columbia.edu/~jeh1/mailings/20080114_GISTEMP.pdf

The additional warming from increasing solar irradiance is 0.3 W/m2 over the next years.

When the Arctic summer sea ice is gone in a couple of years time, the whole weather and climate pattern of the Northern hemisphere will change. We have no idea what that will mean.

Causes of Changes in Arctic Sea Ice; by Wieslaw Maslowski (Naval Postgraduate School)
http://www.ametsoc.org/atmospolicy/documents/May032006_Dr.WieslawMaslows...