Sonoma County – which was hit hardest by the fires – experienced a particularly sharp decline in rainfall between winter and summer (the red line on the chart below shows how 2017 compares to previous years).
Those were specific to Darfur, whereas the sharp drop in rainfall hit the whole Sahel, without intensifying conflict elsewhere.Another commonly cited example is violent competition for scarce grazing between nomadic herdsmen in the Horn of Africa.
A 2012 study in the journal Science analyzed a 2,000 year old stalagmite from a cave in Belize and also "found that sharp decreases in rainfall coincided with periods of decline in the culture," said Discovery.
As shown above, there is a sharp contrast in rainfall between the mid-latitude and low-latitude regions oρf East Asia.
These two regimes induce different dates for the beginning of the rainy season, and account for the sharp variability in rainfall, ranging from 400-800 mm.
But other regions already at risk of severe drought saw sharp decreases — heavy rainfalls occurred 27percentt less often around the Mediterranean region, while the western United States saw a 21percentt decline.
There was a sharp gradient between high rainfall totals in western Scotland and Snowdonia, where rainfall was above average, and dry conditions across parts of southern England.
As temperatures climb and oceans warm, tropical and subtropical regions will face sharp changes in annual rainfall, says the Intergovernmental Panel on Climate Change (IPCC) report, released on Thursday in Stockholm before online publication on 30 September.
Furthermore, we suspect that UK better reproduces the sharp boundaries present in rainfall maps, but that the lack of short-distance monitoring station pairs prevents cross-validation from revealing this effect.
A 10 to 15percentnt increase in monsoon precipitation in many regions of India, a simultaneous precipitation decline of 5 25 per cent in drought-prone central India and a sharp decline in winter rainfall in northern India are projected (Ramesh and Yadava, 2005).
"The evidence is fairly clear that sharp downward deviations from normal rainfall in fragile societies elevate the risk of major conflict," said Marc Levy of the Earth Institute at Columbia University, which recently published a study on the relationship between climate and civil war.
