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'global warming is happening'
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Global warming studies have errors or have not been reproduced.
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Certainly studies of data showing a rising temperature have been reproduced over and over again. Any universal "flaw" in those studies would be pretty subjective. Perhaps you mean something more specific?
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'time travel into the past is possible'
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Many theories of time deal with it was another dimension. While it is more strictly linked to causality and entropy than regular spacial dimensions, it may be only our perspective in it that makes us see any difference. Going back in time may be as simple as taking a step backward for other types of consciousnesses.