As for it's existence, the world has been cycling through climates for some time, I believe.
Scientists have found the 'cycles' are gradually 'speeding up'. The reason? Too much heat.
We can't blame developing countries for buring coal for energy, coal is just so much cheaper and easier than other sources like nuclear or Hydroelectric or even the Wind. However, developed nations should consider 'greener' energy sources, or rectify the problem at its roots : reduce those gas emissions.
And yes, the climate change IS happening. Look at that winter storm that just past California (or was it Florida
), and the increasing strength and occurences of tropical storms around the world.