Why greenhouse effect can be dangerous for our planet?

n - First, there is no direct dokozatelstvo existence of this greenhouse effect. Well, so rubbed that allegedly excess heat , which does not go into space remains in the atmosphere , respectively, the melting of ice in Antarctica and Antarctica ... the fresh water of the ice gets into the Gulf Stream , is disturbed by the lack of salt in the water cycle within it slows down, stops completely , warm air does not extend to Europe and North America