Acceleration?
Possible, I feel the earth and the sun for that matter have cycles.
The earth has a weird orbit, and every every 20K years there are smaller fluctuations, and around 100K the variation is the strongest. This means that the earth is actually closer or further away from the sun than it is normally. I think we could be in one of these cycles, man's influence is there, but not the only factor. IMO. Could it be accelerating because of man, sure.
If human's were to disappear today with no bombs going off. The earth would get hot and cool on its own in the future, because that is what has happened historically.
Here is why I feel this way:
Please notice that normal variation is 3.3-3.4% of earths orbit, but when we are in this cycle the variation is 6.8% or distance from the earth. This is a doubling of the variation. Sometimes closer sometimes further away. Which leads to an Ice age, or hot periods. This is documented and scientifically proven.
The slight ellipse in the earth's orbit does have a slight impact on the amount of solar energy being received by the earth. This 3.3% difference in distance does not impact the earth as much as the seasonal variations, however.
The relative increase in solar irradiation at closest approach to the Sun (perihelion) compared to the irradiation at the furthest distance (aphelion) is slightly larger than four times the eccentricity. For the current orbital eccentricity this amounts to a variation in incoming solar radiation of about 6.8%, while the current difference between perihelion and aphelion is only 3.4% (5.1 million km). Perihelion presently occurs around January 3, while aphelion is around July 4. When the orbit is at its most elliptical, the amount of solar radiation at perihelion will be about 23% more than at aphelion.
The 100,000-year problem is a discrepancy between past temperatures and the amount of incoming solar radiation, or insolation. The former rises and falls according to the strength of radiation from the sun, the distance from the earth to the sun, and the tilt of the Earth's poles. However, the ice-age cycle, which grows and shrinks periodically on a 100,000-year (100 ka) timescale, does not correlate well with any of these factors.
Due to variations in the Earth's orbit, the amount of insolation varies with periods of around 21,000, 40,000, 100,000, and 400,000 years. Variations in the amount of solar heating drive changes in the climate of the Earth, and are recognised as a key factor in the timing of initiation and termination of ice ages. Spectral analysis shows that the most powerful climate response is at 100,000-year period, but the orbital forcing at this period is small.
Somehow this means to show that we are due for a warming cycle.

Quoting my sources:
http://en.wikipedia....00-year_problem
http://en.wikipedia....nkovitch_cycles
http://en.wikipedia....iki/Inclination
http://geography.abo.../a/orbitsun.htm
http://climap.net/100000-year-problem