Is this because of the different places of evolution, the Neanderthals evolving in cold climates during the ice age while humans evolved in the tropics?
This is what's called a secular trend. Changes in height of this nature are related to increases in health and nutrition and are primarily a result of longer limbs (as opposed to torso), rather than evolution.
You can read about secular trends here: http://www.isita-org.com/jass/Contents/2008%20vol86/06_Danubio.pdf
And here is more info on the dutch and height. http://m.huffpost.com/us/entry/5544085