SP has a book review about the fall of Rome being due to climate change.
It wasn't just Rome of course:
He shows how the rise of the empire occurred during a period – “the Roman Climate Optimum” (c. 200 BC-c. AD 150) – of remarkable climatic conditions, which favored agriculture, trade, and population growth. This was followed by a transitional period of erratic climatologic conditions (c. AD 150-450), with frequent poor harvests and plagues, which disrupted and destabilized the entire world – even to China and Peru -- and in Eurasia initiated the “Barbarian” migrations. There followed a period of general cooling – the “Late Antique Little Ice Age” (c. AD 450-c. 700), in which conditions worsened, the Western Empire disappeared, and the Eastern Empire was reduced to a rump state.
I found the audiobook on Scribd and will listen to it when I get around to it.
Right now I am relistening to Mike Duncan's series on the history of Rome: iTunes has it here. but at least some of the podcasts are on youtube and intenet archives.
related item: His present series of podcasts ia on Revolutions: and includes this one about the year of hunger in the 1840s and how it affected Europe.