Hmm. The solar cycle is the only thing I Think can change nature that fast, naturally. But since it's oscillating, so it goes up and down, and it has always been doing it, I don't think it is so serious.
I think the reasons are not only CO
2. But when we are already increasing the temperature, it will begin to increase itself; the methane, a much more powerful greenhouse gas than CO
2, is released into the atmosphere when it's "storages" are destroyed/melting/whatever.
The white ice, which is effective for reflecting the heat, are melting, becoming dark blue ocean, which is good at absorbing the heat and increasing the temperature even further.
We build black roads, and we destroy plants and forests, both directly and from the sulphur we are releasing, and have released in the past.
Of course, if changes couldn't happen over 50 years, they couldn't happen at all. Small changes over short time lead to large changes over long time, like in evolution. But I don't Think the global temperature can change like it has done more than... I don't know! Something small.