Marc Sea-floor drill cores have shown no correlation between the magnetic reversal of the poles, or their absence over prolonged periods of time, and the global temperature. There is a significant increase in high energy solar radiation (cosmic rays,etc) that is normally directed to the polar regions by the earth's magnetic field, striking other areas of the earth, and this can be of serious consequence for increased UVB striking many areas, but not for increased heating. The earth's axis is tilted approximately 23 degrees away from vertical, and during our winter in the northern hemisphere, the earth is approximately 4 million miles closer to the sun (closest Jan 4 each year). If in fact, the poles were to reverse physically,ie.the land mass, it would mean the earth would have to flip over, and there is no suggestion that this is what happens when the magnetic poles reverse. So for the next little while, the closeness to the sun in winter will continue to lessen the impact of our pointing away from the sun at that time but may hasten the impact of global warming on the north pole regions.