Man Made Global Warming

[BaronBonBaron]

"A team of scientists led by geochemist Zunli Lu from Syracuse University in New York state, has found that contrary to the ‘consensus’, the ‘Medieval Warm Period’ approximately 500 to 1,000 years ago wasn’t just confined to Europe.


In fact, it extended all the way down to Antarctica – which means that the Earth has already experience global warming without the aid of human CO2 emissions."

http://thegwpf.org/science-news/5306...new-study.html


Note that I'm not saying the planet isn't warming right now.
My question is: Is their proof that the current 'warming trend' is caused by human activity, and not something that happened naturally like the ‘Medieval Warm Period’?