Why is the US gripped by severe weather?
New research suggests that the main system that helps determine the weather over Northern Europe and North America may be changing.
The study shows that the so-called jet stream has increasingly taken a longer, meandering path. This has resulted in weather remaining the same for more prolonged periods.
The BBC's science correspondent Pallab Ghosh reports from Chicago on why the US has been gripped by such extreme weather patterns.
- From the section Science & Environment