Harvard University paper: Crime decreases when it's uncomfortably cold enough to dissuade people from spending much time outside?

Does global warming increase violent crime? Here's someone who says so. – Telegraph Blogs

He found “a striking relationship between monthly weather patterns and crime rates”, with murders, rapes, assaults and similar crimes increasing in step with temperature. Property crimes, like burglary and larceny, similarly increase as it gets warmer, but only up to the modest level of 40 degrees Fahrenheit, after which the rising thermometer has little effect...violent crime has been decreasing for decades in the US even as global warming has begun to take hold.