Climate change could have been responsible for bringing down the Roman Empire, scientists believe.

Researchers studied ancient tree growth rings to show links between climate change and major events in human history such as migrations, plagues and the rise and fall of empires.　

They discovered that periods of warm, wet weather coincided with period of prosperity, while droughts or varying conditions occurred at times of political upheaval such as the demise of the Roman Empire.

To match the environmental record with the historical one, researchers looked at more than 7,200 tree fossils from the past 2,500 years.

The study, published in the journal Science, said: 'The rise and fall of past civilizations have been associated with environmental change, mainly due to effects on water supply and agricultural productivity, human health and civil conflict.

'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.

'Distinct drying in the third century paralleled a period of serious crisis in the western Roman Empire marked by barbarian invasion, political turmoil and economic dislocation in several provinces in Gaul.'

Oak rings are sensitive to changes in precipitation, and can show changes according to what was happening in the environment.

The research could also glean signs about what was happening from changes in how many trees were being cut.

The study said: 'Reduced tree harvesting around AD 250 to 400 coincides with the biggest central Europe historical crisis, the Migration Period, a time marked by lasting political turmoil, cultural change and socio-economic instability.

'Increasing timber harvest for construction is represented by abundant felling parallel to socio-economic consolidation from the sixth to the ninth centuries.'

The scientists said 'unfavourable climate may have contributed to the spread of the second plaguepandemic, the Black Death, which reduced central Europe's population after AD 1347 by 40 to 60 percent.'

Researchers also noted that a sharp decline in North American temperatures around the same time saw an 'abrupt desertion of former Greenland settlements'.

Technological advances have made the modern human population less vulnerable to environmental changes to a certain extent, the study said.

However we are 'certainly not immune to the predicted temperature and precipitation changes, especially considering that migration to more favourable habitats as an adaptive response will not be an option in an increasingly crowded world.'