These events could unleash public unrest, cross-border conflicts and mass migration as people flee from the worst-affected regions, he warned.

Before the outbreak of violent conflict in 2011, Syria had endured four consecutive years of drought in the North-eastern part of the country, particularly in Al-Hasakeh, Deir Ezzor and Al-Raqqa.

Crop failures and drought had already taken their toll on 1.3 million people with nearly 800,000 losing their livelihoods. Thousands migrated from the North-eastern areas and moved to informal settlements or camps close to Damascus.

Olivier de Schutter, United Nations special rapporteur on the right to food, warned in 2010 that Syria's drought was affecting food security and had already pushed nearly 3 million people into extreme poverty.

The severity of the 2006 to 2010 drought and the failure of Bashar al-Assad’s regime to prepare, or respond to it effectively, exacerbated other tensions, from unemployment to corruption and inequality, which erupted in the wake of the Arab spring revolutions.

Francesca de Châtel at Radboud University in the Netherlands said that rural communities had been disenfranchised and disaffected after 50 years of policies that exploited and mismanaged Syrian resources.

The link between climate change and conflict has been debated for years. A working group of the Intergovernmental Panel on Climate Change wrote in 2014 that there was “justifiable common concern” that climate change increased the risk of armed conflict in certain circumstances, but said it was unclear how strong the effect was.

Oxfam has launched a call for help for those in the refugee camps in Jordan, Lebanon and across conflict lines in Syria. It is also working refugees in Italy and Sicily.

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