Discussion: Kosher?
in: blairtrewin; blairtrewin > 2015-03-28
Mar 28, 2015 9:50 AM
#
feet:
Seems so to me but I am an expert neither in the underlying data nor in the details of the econometrics.
http://www.voxeu.org/article/myth-europe-s-little-...
http://www.voxeu.org/article/myth-europe-s-little-...
Mar 31, 2015 9:50 AM
#
Presumably there's some analysis underlying their conclusions, but as it stands they haven't presented any evidence beyond visual inspection that the data match a white-noise process.
To some extent they're attacking a strawman, as it is not generally claimed that temperatures declined through the period they're reviewing. Rather, the concept of the 'Little Ice Age' is one of temperatures which were cooler (at least in northwest Europe) between 1300 and 1900 than in the centuries preceding it - the assessment of the last IPCC report was that, at least on centennial timescales, Northern Hemisphere temperatures were fairly stable between 1300 and 1900, and a few tenths of a degree cooler than those between about 1000 and 1300. (Whether 1000-1300 temperatures are slightly warmer or slightly cooler than the 20th century average is a debate which induces a similar passion, and is of similarly limited relevance, to those which occurred in the Middle Ages over the question of how many angels could dance on the head of a pin).
It's clear from the data presented that there are occasional periods when warm summers are almost entirely lacking for periods of 30 years or more (e.g. around 1800). A reasonable case can be made that such periods would occur in random data (and can thus be interpreted as simply a function of inherent natural variability of the climate system), but they still have real impacts whatever their cause.
I'd also agree with the suggestion that comparative advantage (or the absence thereof) probably had as much to do with the decline of climatically marginal agricultural areas as cooler temperatures did, and that the impacts of relative warmth around 1000 are overstated - I've sometimes been known to suggest that Erik the Red's naming of Greenland is the world's first documented instance of misleading marketing claims by promoters of a real estate development. That said, there is ice core evidence to suggest that the highest decadal mean temperatures in Greenland in the 1000-1300 period were not surpassed until the 2000s.
To some extent they're attacking a strawman, as it is not generally claimed that temperatures declined through the period they're reviewing. Rather, the concept of the 'Little Ice Age' is one of temperatures which were cooler (at least in northwest Europe) between 1300 and 1900 than in the centuries preceding it - the assessment of the last IPCC report was that, at least on centennial timescales, Northern Hemisphere temperatures were fairly stable between 1300 and 1900, and a few tenths of a degree cooler than those between about 1000 and 1300. (Whether 1000-1300 temperatures are slightly warmer or slightly cooler than the 20th century average is a debate which induces a similar passion, and is of similarly limited relevance, to those which occurred in the Middle Ages over the question of how many angels could dance on the head of a pin).
It's clear from the data presented that there are occasional periods when warm summers are almost entirely lacking for periods of 30 years or more (e.g. around 1800). A reasonable case can be made that such periods would occur in random data (and can thus be interpreted as simply a function of inherent natural variability of the climate system), but they still have real impacts whatever their cause.
I'd also agree with the suggestion that comparative advantage (or the absence thereof) probably had as much to do with the decline of climatically marginal agricultural areas as cooler temperatures did, and that the impacts of relative warmth around 1000 are overstated - I've sometimes been known to suggest that Erik the Red's naming of Greenland is the world's first documented instance of misleading marketing claims by promoters of a real estate development. That said, there is ice core evidence to suggest that the highest decadal mean temperatures in Greenland in the 1000-1300 period were not surpassed until the 2000s.
This discussion thread is closed.