Yglesias wants to scare about the expected climate change and refers to some obscure statistics which asserts that even in the US "productivity of individual days declines roughly 1.7% for each 1.8°F increase in temperature above 59°F". But with statistics you can make up everything you want: For instance statistics allegedly "proof" a relationship between "stork population and human birth rate in Europe", "beer drinking in the USA and children mortality in Japan" and more nonsense (pbil relationship).
Yglesias thesis does not stand reason. I remember the winter 2013/14. In the first quarter of 2014 the US GDP dropped 2.9% because of snow and extremely low temperatures (forbes). Each winter season in the north of the US and Europe construction, agriculture, transport and other industries are slowing down - or come to a standstill - because of winterly conditions. This weekend for instance many flights in the US north-east are cancelled because of heavy snow (nbcnews). Snow & ice cause huge travel delays and a lot of canceled flights and are reducing security, comfort & productivity painfully. People die because of traffic accidents caused by icy streets or snowy streets slow the emergency cars. Some even freeze to death.
From around 1550 till 1850 Europe suffered the so-called "little ice age" with very chilly periods (wikipedia). Low temperatures, long winters & short - or no - summers destroyed the crops and caused famines & deathly flu epidemics. In the 19th century temperatures started climbing and Europe`s economical and political rise began - coincidence?
People can protect themselves against heat thanks to air condition. I stayed once in a hotel room in tropical Thailand which had no air conditioner but a huge fan on the ceiling cooled the place properly. Ice and snow still create a lot of problems as we can see these days in the troubled US north east.
Warm temperatures don´t detain productivity and economic growth. Singapore - which is very close to the Equator and has a hot & humid climate - is a vibrant and economical very sucessful state. The southern Chinese metropolises Hong Kong and Shenzen - with a mostly tropical climate - are the most dynamic parts of the people`s republic. And Phoenix (Arizona) and Austin (Texas) belong to the most dynamic US cities.
If the earth gets significantly warmer then the permafrost regions of Siberia, Canada and Alaska will thaw and will boost global agriculture. We could expect more wheat, corn and other crop. And free seaways along Sibiria`s and Canada´s north coast should boost global transport.
In January we escaped the New York winter and spend some days on the tropical American Virgin Islands (driveby). We enjoyed the warm climate very much and the natives were friendly and relaxed. Some like it hot.