For two weeks, computer models teased the possibility of Britain reaching 40 Celsius (104 degrees) this week, a level unsurpassed since at least 1850 - and probably in more than 6,000 years. Meteorologists gazed at these model forecasts in disbelief, skeptical that such predictions would come true. Six days ago, the U.K. Met Office put the odds of hitting 40 Celsius at only 10%. But the seemingly unlikely model forecasts proved correct. London Heathrow was among six locations in the United Kingdom to top 40 Celsius on Tuesday, shattering Britain's all-time temperature record. This is the latest example of how...