Global climate change (not the cliche'd term: global warming), is a cyclic event that occurs with or without human affect.

There are several variables that can contribute to climate change, be it volcanos, solar flares and sun spot activity, methane deposit eruptions, etc.

HOWEVER, the effect can be accelerated by irresponsible behaviour on our part and I'd bet it has.

The Earth will warm and cool and warm and cool regardless of what we do or don't do. But we must be diligent and treat the Earth kindly or we'll be the next mass extinction.

Great wallpaper, Kiriapurv. I really like it very much, but I think the global warming is caused not only by cars and planes, but by the meat consumption. If any one is interested to check:

http://www.suprememastertv.com/SOS-Global-Warming.php

Another one of those environmentalism bullshit themed wallpapers?

Global warming is NOT caused by men and women driving cars. If it was, how would you explain vikings being able to grow grapes on Greenland a thousand years ago?

How do you explain temperatures rising on Mars?

read this article and say
http://news.nationalgeographic.com/news/2004/12/1206_041206_global_warming.html

Vikings: Local fluctuation
Mars: Increase in solar output?

Who made cars ? dinosaurs ?

yeah youre right, as the vikings certainly didnt have cars and they had warmer temperatures then today, there could be no relations between cars and rising global temperature. also as they didnt have any guns, but certainly killed people, there is no chance that people could be killed with guns (dont try this at home), because the same effect cant possibly be caused by different things...

for your questions you might want to do the obvious: read some basic information about the phenomena you described (i.e. Wikipedia) and you might find out, that afaik the so called "Medieval Warm Period" was most certainly a local and no global climate phenomenon, and about the mars i can only guess, that because of the lack of an atmosphere its temperature is nearly directly generated by the variation of sun radiation. Anyway, your lack of information about other climate events is no argument against the scientifically well documented anthropogenic climate change taking place in the present.