Did global warming cause the decline of the Roman empire?

2500 Years of European Climate Variability and Human Susceptibility | Science/AAAS: Recent warming is unprecedented, but modern hydroclimatic variations may have at times been exceeded in magnitude and duration. Wet and warm summers occurred during periods of Roman and medieval prosperity. Increased climate variability from ~AD 250 to 600 coincided with the demise of the Western Roman Empire and the turmoil of the Migration Period.