From: petertrei@gmail.com   
      
   On 2/20/2026 6:27 PM, Lawrence D’Oliveiro wrote:   
   > On Fri, 20 Feb 2026 16:53:53 -0500, William Hyde wrote:   
   >   
   >> But getting the temperature up to the point that liquid water won't   
   >> all condense in ice caps is also a difficult problem. The CO2 levels   
   >> required are very toxic. We need a molecule which is strongly   
   >> absorbing in the IR, chemically neutral, and which does not   
   >> disassociate into something damaging in the upper atmosphere when   
   >> struck by UV radiation.   
    > > Or alternatively, we need to reengineer the human species to be more   
   > tolerant of unEarthly conditions. For example, did you know that we   
   > have difficulty breathing in an oxygen concentration below about 15%?   
   > (I suspect birds can do better than that.) That’s not that far below   
   > normal Earth-atmospheric amount of 20%.   
      
      
   We can do better then that with training. La Rinconada, Peru, is at   
   16,700 feet, and low pressure lowers the equivalent O2 fraction to   
   about 11%. You definitely need acclimatization, but people live there   
   year round.   
      
   pt   
      
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