In the Breitbart article, James Delingpole does a pretty good job in debunking Al Gore's claim that global warming has led to Brexit. The other claim mentioned in the article that Type 2 diabetes is becoming more common due to global warming also looks a bit dubious:
I believe that the background to this idea is that the increasing prevalence of Type 2 diabetes is supposedly partly caused by there being a greater tendency for people to live in well-heated homes with central heating. The other more well-known causes for people susceptible to Type 2 diabetes are being significantly overweight, eating too much refined sugar, and taking little or no physical exercise. Before central heating became common, people were more likely to be exposed to cold temperatures which apparently causes 'brown fat' or 'brown adipose tissue (BAT)' to be more readily burned off by the body, and this affects blood sugar levels. Exposure to cold temperatures also of course increases the risk of picking up colds, flu and other infections, so it is unlikely that public health advisers would ever suggest that people try to avoid or reduce the severity of Type 2 diabetes by keeping themselves cold.
To investigate the temperature dependence issue properly, you would I think need to know what the average annual temperature, both indoor and outdoor(with the indoor temperature probably the more important of the two), that a person experiences in various geographical areas and know what the temperature variation is from one year to another. But the researchers only have access to the outdoor temperature values, and so the paper is just based on that.