In the latest bid to get us to cut greenhouse gases, scientists have decided that eco-conscious aliens disgusted by mankind's emissions could destroy our planet in disgust. When observed from afar, the changes in Earth's atmosphere could label us as a civilisation that has grown out of control. Aliens reaching that conclusion may then launch a pre-emptive attack to protect this perceived threat to their own way of life.
But that is only one possibility. Scientists are also considering other unwelcome - and far-fetched - outcomes, such as aggressive extra-terrestrials who eat or enslave us, or perhaps they are industrial types who want to improve their own technological infrastructure and so pillage ours.
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