'The observed increase in the frequency of previously rare summertime-average temperatures is more consistent with the consequences of increasing greenhouse gas concentrations than with the effects of natural climate variability, said Duffy. 'It is extremely unlikely that the observed increase has happened through chance alone.'
The team also modelled the period 2035-2064.
'What was historically a one in 20-year occurrence will occur with at least a 70 percent chance every year,' said Duffy 'This work shows an example of how climate change can affect weather extremes, as well as averages.'
Full report on ScienceDaily