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