the great drought of the 1980s. During the same period in much of East Africa, rainfall trends have declined.39-42
From 2012 through 2015, California experienced the most severe drought in the last 1,200 years.43
A range of scientific
research has suggested a link between anthropogenic warming and an increase in the occurrence, strength, and length of high impact droughts in this region of the U.S. The economic impacts of drought on California agriculture in 2015 alone were estimated at US$2.7 billion.44
About 60 per cent of water supply to California comes from groundwater.45 The
groundwater storage has been overdrawn for many decades. The long period of drought drastically increased groundwater withdrawal and, as a result, lowered the groundwater level and storage capacity.46
Reduced rainfall also means less
replenishment for the underground aquifer. This has led to an irreversible aquifer-system compaction, causing the land to subside. In 2014 a large area measured 96 kilometres long subsided further by 33 centimetres as a result of this recent drought.47
Temperature anomaly in the Central and Western Europe Legend -10 -10 Source
Courtesy of Reto Stockli and Robert Simmon, based upon data provided by the MODIS Land Science Team. Columbia Research Institute for Climate and Society, Columbia University.
Source: Alessandra Giannini, IRI, Columbia University Years <-14 -12 -10 -8 -6 -4 -2 0 2 4 6 8
Temperature Anomaly in the Central and Western Europe Annual Temperature Anomaly [°C]
0 Monthly Temperature Anomaly [°C] 0 10 10
Source: CIESIN, based on CRUTS3.22: Climatic Research Unit (CRU) Time-Series (TS) Version 3.22
Trend in Annual Surface Temperature (1951-2013) in degrees celsius per decade <0.1 0.1 0.2 0.3 0.4 .51 Coefficient of variation of rainfall from 1951-2013 (in % of the long term average) Source: Millenium Ecosystem Assessment Semi-arid Drylands Temeperature Change from 1951 - 2013
Temperature and rainfall variation in East and West Africa
Temperature and rainfall variation in East and West Africa Semi-arid drylands of East and West Africa
Source: CIESIN, based on CRUTS3.22: Climatic Research Unit (CRU) Time-Series (TS) Version 3.22
Coefficient of Variation of Rainfall (1951-2013) in Percentages <10 10 15 20 25 30 35 40 45 50 104
Difference in the number of years that received adequate rain fall for sorghum and millet (1990-2009 compared with 1950-1969) (450 mm threshold)
Land subsidence in California from 1988 to 2013 © USGS/Justin Brandt
Land subsidence in California from 1988 to 2013 ©USGS/Justin Brandt
47
UNEP FRONTIERS 2016 REPORT
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