Some of the ugliness in the news this week – several killings in Philadelphia, 100 teenagers involved in a Center City fracas -- has been almost a counterpoint to one of the more-magnificent stretches of March weather in the period of record.
But could the ugliness be related to that magnificence?
Various research has shown a correlation between rising temperatures and violent crimes, but a recent paper out of the University of Albany, which looked at U.S. large cities, noted an important exception – homicides.
Our own non-peer-reviewed research using Uniform Crime reports reached a similar conclusion. We looked at aggravated assaults and homicides for Januaries and Julys in the Philadelphia region.
We picked those because climatologically January is the coldest month, and July, the warmest. Plus they each have 31 days, which makes the comparison tidier. The data was available back to 2006.
We found quite a difference in the aggravated-assault figures for January and July. The January average was 520 cases, compared with 636 for July.
Homicide figures, however, were virtually identical – 24 each.
Having delved into this field of biometeorology – that's the effects of weather on the body – we know that we are entering murky waters.
The process of distilling atmospheric variables from other causes is a maddening one.
As researcher Ellen G. Cohn noted in a 1990 paper in the British Journal of Criminology, the obstacles to drawing conclusions about crime and weather include inadequate sample sizes, weak or inappropriate statistical techniques, and poor control of extraneous variables."
That said, our informal study shows that about 99.9999 percent of the region's population have managed to enjoy this week's weather without incident.