Of course they occurred; at least an overwhelming amount of evidence points to the fact that they did.
Of course the warming and cooling experienced during those periods was between .5 and 1.5 degrees celcius. It also changed over a 3-400 year period. We have experienced the 1 degree celcius change in less than a century and are looking at up to 3 degrees over the next. As I have previusly mentioned, it might just be terrible timing that we are combining man-made influences with natural cycles to produce a much greater than natural change.
Check out post 22 and in particular this paragraph in the source link.
"Interestingly, during the 20th Century, the Sun’s magnetic field which shields Earth from cosmic rays more than doubled, thereby reducing the average influx of cosmic rays. The resulting reduction in cloudiness, especially of low-altitude clouds, may be a significant factor in the global warming Earth has undergone during the last century. However, until now, there has been no experimental evidence of how the causal mechanism linking cosmic rays and cloud formation may work."