Chilling Effects
People continue to point out the (widely known) negative effects of global warming, but how are we so confident that the <i>net effects</i> will be long-term negative?[1] It seems to me an extremely complicated calculation which doesn't merit extreme certainty in either direction.  Here are some of the positives of global warming:<p>- Statistically, an order of magnitude more humans die from colder temperatures than from hotter ones (as discussed in this article).  So hotter temperatures could easily lead to net lives saved, at least in this area.<p>- Hotter temperatures and higher CO2 in northern/arctic areas will increase (net) crop yields substantially.  Many areas which formerly weren't hospitable for certain types of crops will suddenly become so. This isn't so surprising since CO2 is an input to photosynthesis.<p>- Global warming will free up northern trade routes and make potentially millions of square miles of land more habitable for humans.<p>- The distribution of global temperature increases is expected to be tilted towards colder areas (that is: higher temperature increases in colder regions than in hotter regions).  This means we get to experience the positive effects of global warming disproportionately to the negative effects.<p>- Slight temperature increases might even hedge against long-term climate risk: we are technically still in an ice age, and there is long-term tail risk that we will recede back into a deeper one within a few millennia.  So how do we <i>know</i> that stopping CO2 emissions won't make human climate long-term worse?<p>- Even from an ecological standpoint: hotter climates will positively impact some species (including species which don't even exist yet!), while negatively impacting others.  It seems to me a general rule of thumb that more life flourishes in hotter climates than colder ones. So why be so confident that the net effects of global warming will be long-term negative to animals, <i>en totale</i>?<p>Of course, the <i>negative</i> effects of global warming (flooding, rising sea levels, etc) are well-known, so I omit them.  My point is not that global warming is definitely a net positive; it's that it's not clear why there is so much confidence it's "definitely" a net negative.<p>[1] Credit to David Friedman for helping point out many of these things.