| Summary: | The extreme meteorological surface air temperatures recorded to date are –89.2 oC in Antarctica, and 56.7 oC in Death Valley, California. Ground temperatures can be higher or lower than these air temperatures. The bulk of oceanic water is cold (< 4 oC) and thermally stable. Whilst data on limits to survival attract considerable attention, the thermal limits to completion of the life cycle (which define the limits to life) are much less well known. Currently identified upper thermal limits for growth are 122 oC for archaeans, 100 oC for bacteria and ~60 oC for unicellular eukaryotes. No unicells appear to grow below –20 oC, a limit that is probably set by dehydration-linked vitrification of the cell interior. The lower thermal limits for survival in multicellular organisms in the natural world extend to at least –70 oC. However in all cases known to date, completion of the life cycle requires summer warmth and the lowest temperature for completion of a multicellular eukaryote life cycle appears to be ~0 oC for invertebrates in glacial meltwater and ~–2 oC for marine invertebrates and fish living on the continental shelves around Antarctica.
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