Unusual weather temperatures last winter and this spring made me wonder why this might be happening. I found the following graphic from Intergovernmental Panel on Climate Change a useful way to think about how extreme fluctuations in weather could occur. Here’s the graphic depicting three scenarios leading to increased weather fluctuations.
- An increase in the mean: the ‘normal’ weather distribution is shifted right, panel A, associated with greater probability of extreme hot weather and less cold weather.
- An increase in variance: the weather distribution is wider at both tails of the distribution, panel B, associated with greater probabilities of both record hot and cold weather.
- An increase in the mean and variance: the weather distribution is shifted right with a longer tail on the left side of the distribution, panel C, associated with less cold weather and greater probabilities for record hot weather.
Note the probability of occurrence of extreme weather (vertical axis) increases in each scenario. According to IPCC these scenarios argue against the claim “the greater the extreme, the less global warming has to do with it.”