Global warming does not just mean warmer summers. The higher temperatures mean more ice melt and higher levels in some bodies of water. That all impacts winter weather too. In fact, warmer summers means colder winters, so more extreme weather is a result that can happen any time of year.
I believe global warming is responsible for the extreme weather we are currently experiencing but that doesn't really touch on the subject of rather the current warming trend is natural or rather it is a man-made warming trend. I believe it is normal for the temperatures to fluctuate and I believe it is normal to have warmer and colder periods over large amounts of time. Unfortunately, I guess we will have to wait to see if our damage will make it go farther than it would naturally.
Global warming or, as the more proper name it is, man made global climate change, is definitely contributing to the strange and extreme wealth patterns that we are experiencing today in the world. A warming world leads to warmer weather which increases water in the atmosphere and throws off the climate.
The theory behind global warming is not only going to warm the planet slowly, but also change up the weather patterns we see. Cold places will get warm snaps, warm places will get cold snaps, and the amount of precipitation places get will change a whole lot, making everything change.
Yes, global warming is responsible for the extreme weather we have been seeing the last decade. And this isn't up for debate. Earth and climate scientists the world over agree that global warming is creating these monstrous storms and bizarre seasonal conditions. This is only a debate among laymen. Not professionals.