Global Warming and Productivity

A recent post at Monkey Cage tells about predictions that global warming will decrease productivity.  Studies in Tokyo point out that for every rise in temperature above 25C (77F) productivity declines by about 2%.

What they fail to take into account is that the average global surface temperature is much lower than 77F (25C).  In fact, as NASA points out at the bottom of this page, it is about 14C (57F).  Here is a more complete description of the effect of temperature on productivity.  Note that the optimum temperature for productivity is between 70F (21C) and 73F (23C), well above average surface temperatures for the earth as a whole.  Actually studies differ on what temperature is optimal, some placing it as high as 77F.  But I suspect there is little disagreement on whether 57F is hotter or colder than this ideal temperature.  Further, the graph on the page shows that productivity falls much faster for excessively cool temperatures than for excessively warm ones.

I suspect that what the study that fears a decline in productivity is noticing is that people in many of the less affluent countries are much less likely to have access to air conditioning than heat.  Hence they deal with excessively cool temperatures much better than with excessive heat.

A factor in favor of the argument that global warming is likely to decrease productivity is that temperatures during the day are generally higher than those at night.  Hence average daytime temperature is likely to be higher than average and more likely to be above the optimum.  The high temperature for a day may be 20F higher than the low.  However, for much of the day the temperature will be somewhat less than the high.  Hence a typical daytime temperature is still likely to be much less than the optimum.

In any case humans can easily adapt to warmer temperatures by either using heaters less and air conditioners more or migrating further from the equator.