Table 6.

List of macro-regional extreme drought events from 1951 to 2016 according to the SPEI-12. An event is defined extreme if the special score is larger than 12 (see Table 3). DS means drought severity, DI drought intensity, DA the average percentage of area in drought, and Sc is the special score. Due to space constraints, we report only the name of the leading author of the references, but in the references section we include the entire citation. The events “ending” on December 2016 could extend into 2017 or 2018.

#	Name	Reg	St	En	DS	DI	DA	Sc	Main reference(s)	Remarks
1	Scandinavia, Russia 1952	NEE	12/51	09/52	15.9	1.6	46.1	13	Briffa et al., 1994	Pan-European drought in the early 1950s.
2	U.S. (Texas) and Mexico 1951–57	CAM CNA ENA	12/51 09/52 07/55	06/54 05/57 06/56	35.0 83.8 19.6	1.1 1.5 1.6	30.8 40.7 32.5	13 17 14	Woodhouse and Overpeck, 1998 Liverman, 1999 Cook et al., 2007 Seager et al., 2009 Méndez and Magaña, 2010	Southern Texas, Northern Mexico above all, low precipitation. Severe as the Dust Bowl in the 1930s, involved mostly Central and Southern Great Plains, Central U.S. but also Eastern US and Florida.
3	Central Australia 1957–58	SAU	09/57	09/58	20.4	1.6	60.9	14	Heathcote, 1969	Central Australia, especially the outback, little long-term damages to vegetation.
4	UK, Northern Europe, Russia 1959–60	NEU NEE	06/59 06/59	08/60 06/61	30.7 39.1	2.0 1.6	60.0 40.7	18 17	Marsh et al., 2007 Meshcherskaya and Blazhevich, 1997	Excessive sunshine, very low cloudiness, low humidity, heatwave, impacts on crops especially in the U.K. In Russia and Eastern Europe, yield decrease (especially grains) was remarkable.
5	Argentina, Uruguay 1961–64	CSA SSA	11/61 03/62	10/64 08/63	53.4 26.3	1.5 1.5	34.6 45.8	15 14	Sheffield and Wood, 2007 Boulanger et al., 2005	La Niña event caused dry conditions over Eastern Southern South America. This event was similar to the one in 1988, droughts linked with La Niña are uncommon
6	Tibetan Plateau 1962–64	TIB	07/62	01/64	25.7	1.4	32.9	12	Zhu et al., 2011	Low precipitation from 1961 onwards, effects in 1962. Anomalous circulations over Pacific and Indian Ocean, together with anomalous monsoon season partly drove the drought.
7	North-Eastern U.S., Great Plains 1962–64	ENA CNA	06/62 06/63	07/64 01/65	34.1 28.4	1.3 1.4	32.4 33.5	12 14	Seager et al., 2012 Schubert et al., 2004	Northeastern North America involved, New York City experienced problems. This event was a break during wetting trend years. Unusually long dry-inducing atmosphere circulation, extreme negative Northern Atlantic Oscillation, and Northern Pacific sea surface temperature anomalies.
8	Argentina, La Plata Basin 1967–72	CSA SSA	01/67 05/68	01/72 10/72	77.1 49.8	1.3 0.9	31.5 33.8	16 13	Rivera and Penalba, 2014 Minetti et al., 2007	Central and Western part of Southern South America, involved in particular semi-arid areas, but also the La Plata river basin. Negative sea surface temperature anomaly due to El Niño, corn productivity decreased in many areas in this region.
9	Alaska, Canada 1969–70	ALA	01/69	08/70	31.5	1.6	40.7	16	Xiao and Zhuang, 2007	1969 was an exceptional year for forest fires, reinforced by drought in Alaska and Canada
10	Australian Queensland 1969–70	NAU	08/69	03/71	25.3	1.3	51.6	14	Queensland Government, 2009	Queensland drought in 1969–70 was mainly due to prolonged lack of rain.
11	India 1972–73	SAS	07/72	07/73	26.4	2.0	43.0	18	Kanamitsu and Krishnamurti, 1978	Circulation anomalies (hypothesis), summer monsoon was anomalous.
12	European Russia 1972–73	NEE	06/72	09/73	33.3	2.1	47.9	16	Bradford, 2000	Very dry winter in Eastern Europe and Russia, where some rivers recorded lowest levels of the 20th century.
13	Tibetan Plateau, Mongolia 1974–76	TIB	05/74	07/76	33.3	1.2	31.7	12	-	-
14	U.K., Baltic Republic, Russia 1975–77	NEE NEU	05/75 12/75	08/76 06/77	34.6 35.8	2.2 1.9	54.9 56.7	17 17	Sheffield et al., 2009 Perry, 1976	The drought involved the Baltic countries and moved eastwards in 1976 until the Caspian Sea. Drought due to low/very low rainfall, especially over England and Wales.
15	U.S. Great Plains 1976–77	CNA	07/76	11/77	33.0	1.9	46.5	17	Diaz, 1983	Spring drought (1997 and afterwards), due to very dry weather conditions over Central and Western United States
16	Western U.S., Central Plains 1977–82	ALA CNA	09/76 07/80	09/81 04/82	54.4 31.0	0.9 1.4	29.1 38.1	12 14	Karl and Quayle, 1981 Namias, 1982, Namias, 1983	Extensive drought over the Central Plains, in summer 1980 an exceptional heatwave (up to + 4.5 °C), lack of cloud cover caused relative humidity to be very low during the day also over Central U.S. However, precipitation were not so low.
17	Southeast Asia, Pacific Islands 1982–83	SEA	10/82	11/83	24.7	1.8	45.2	15	Quiroz, 1983 Gibbs, 1984 Kiladis and Diaz, 1986	Coupled with a strong El Niño event (anomalous climate conditions), this drought hit Indonesia, Papua, the Philippines, Borneo, northern Australia.
18	Sahel drought 1983–88	WAF EAF	03/83 02/84	07/88 08/85	99.2 39.9	1.5 2.1	45.7 49.0	18 17	Henricksen, 1986 Gommes and Petrassi, 1996 Hulme, 2001	The mid-1980s Sahel drought was driven by low precipitation from the early 1980s and resulted in extended desiccation and degradation of large areas. The drought hit Ethiopia in 1983–84 with important impacts.
19	Conterminous United States 1985–91	ENA CNA WNA	05/85 10/87 10/87	05/89 11/90 05/91	61.9 46.6 50.9	1.3 1.2 1.2	29.1 36.2 31.6	14 15 12	Andreadis et al., 2005 Kogan, 1995 Peters et al., 2002	Very long drought in the conterminous U.S., sources report 4–7 years of consecutive drought conditions. This is also considered a soil moisture and runoff drought. Vegetation impacts were outstanding and are clearly visible from satellite images.
20	Patagonia 1988–90	SSA	11/88	03/90	31.6	1.9	55.9	16	Rivera and Penalba, 2014	Drought over Patagonia and Central Southern South America, with large impacts on grain production and hydroelectric power production. Coupled with La Niña event.
21	Balkans, Greece 1989–91	MED	03/89	06/91	35.4	1.3	33.0	14	Tselepidaki et al., 1992	Low precipitation over Greece and the Balkans triggered drought conditions.
22	Philippines, Indonesia 1992–93	SEA	10/91	07/95	47.1	1.0	30.2	13	Salafsky, 1994 Hilario et al., 2009	Strong (but not exceptional) 1991–92 El Niño event, drought involved the Philippines (large impacts) and Indonesia.
23	Northeastern Brazil 1992–93	AMZ	01/92	10/93	30.9	1.4	35.7	12	Rao et al., 1995	Drought followed a dry period in northeastern Brazil and the Amazon forest.
24	Southern Africa 1992–93	SAF	02/92	09/93	27.3	1.4	43.3	12	Unganai and Kogan, 1998 Eldridge, 2002 Munro, 2006	Rivers dried, millions of cattles died, cereal production dropped, 86 million people affected, malnutrition problems in Zimbabwe.
25	Western U.S., Mexico 1994–97	ALA WNA	08/94 07/94	06/97 05/95	50.7 15.0	1.5 1.4	37.4 36.5	15 13	Hayes et al., 1999 Chávez, 1999	Drought hit more Western and Southwestern U.S. in 1995–96. Over Northern Mexico, the Rio Bravo region suffered the largest impacts.
26	South Africa, Botswana 1995–96	SAF	12/94	01/96	23.5	1.7	52.4	14	Mussá et al., 2015	Drought over South Africa and Botswana, named the worst drought in 70 years in the Crocodile river catchment. Groundwater was used as emergency source.
27	U.K., France, Denmark 1996–97	NEE	02/96	04/97	22.3	1.5	35.7	12	Fleig et al., 2011 Parry et al., 2012	United Kingdom and Denmark involved above all, hydrological issues, many river catchments in England recorded low levels.
28	Southeast Asia 1997–98 (El Nino)	SEA TIB	09/97 08/97	12/98 07/98	34.0 18.3	2.1 1.5	53.7 32.9	19 13	Nakagawa et al., 2000 Ronghui et al., 2000	Drought coupled with El Niño event in 1997–98. Relevant forest impacts, summer climatic anomalies. In southeastern Asia and the Pacific Islands, El Niño 1997–98 was a super event. Over Borneo, Indonesia, and Eastern Asia fires aggravated drought and vice versa.
29	Central Amazonia 1997–99	AMZ	10/97	03/99	29.3	1.6	40.6	13	Williamson et al., 2000 Nepstad et al., 2004	Increased mortality rate of trees in Central Amazon.
30	Central Asia, Pakistan, China 1999–03	CAS EAS	02/99 08/99	03/02 08/03	71.0 61.1	1.9 1.3	52.5 31.9	19 12	Barlow et al., 2002, Barlow et al., 2016 Kogan, 2002 Zhang and Zhou, 2015	Cold sea surface temperature anomalies over the Indian Ocean and the Western Pacific. Worst drought in Pakistan and Afghanistan in 50 years. Drought peaked over northern China and the Yangtze river basin was heavily impacted, causing great crop losses.
31	Western U.S. and Canada 2000–04	WNA	07/00	08/04	58.8	1.2	31.7	15	Seager, 2007 Woodhouse et al., 2010 Schwalm et al., 2012	This drought peaked in 2002, lasted from 2000 to 2004 and was defined the worst in 800 years regarding impacts on forests and empty rivers. Carbon sequestration cut by 51%.
32	Balkans, Greece, Cyprus 2000–02	MED	06/00	09/02	40.1	1.4	38.9	14	Pashiardis and Michaelides, 2008 Stagge et al., 2013	Drought over southeastern Europe, the Balkans, Greece, and countries over the Aegean Sea. A combination of hot summer temperatures and low rainfall was the cause.
33	India 2002–03	SAS	06/02	09/03	24.5	1.5	38.9	14	Dutta et al., 2015	All-India drought year, big problems for agriculture in Rajasthan, Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Karnataka, and Tamil Nadu. Anomalous monsoon caused floods after drought.
34	Tropical Africa, Congo river basin 2002–06	EAF EQF	05/02 11/03	07/03 11/06	21.9 54.1	1.5 1.5	34.7 36.1	13 18	Calow et al., 2010 Zhou et al., 2014	More than one African region affected, wide surface involved, groundwater affected over central Africa. Forest degradation and decreased greenness could be observed with remote sensing images over forests in the Congo river basin.
35	European heatwave-drought 2003	NEU	03/03	08/04	31.5	1.8	51.0	16	Fink et al., 2004 Ciais et al., 2005 Rebetez et al., 2006	Summer 2003 heatwave over central Europe caused a lot of deaths (especially in France), primary productivity reduction, crop failures, impacts also on natural vegetation. The heatwave lasted from March to September.
36	SW China, Yangtze River basin 2004–10	EAS TIB	07/04 08/06	04/10 01/10	118.0 52.2	1.7 1.2	34.0 34.3	18 16	He et al., 2011 Barriopedro et al., 2012, Yang et al., 2012 Zhang et al., 2013	In 2006–07 an extreme drought hit Sichuan and the Yangtze river basin, causing a fall in production of rice, potatoes, and beans. The drought moved to Yunnan and Southwestern China in 2008–09. It was assumed that an anomalous monsoon season over India pushed extreme drought conditions over southwestern China.
37	U.S. Great Plains and Canada 2006–07	CNA	06/05	05/07	20.4	1.7	43.2	14	Dong et al., 2011 Basara et al., 2013	Drought in the U.S. Great Plains and Canada, causing impacts in many sectors. Positive pressure anomalies over Southwestern deserts combined with negative anomalies over the Great Lakes.
38	The Millennium Drought (Aus) 2006–10	SAU	10/06	08/10	51.7	1.1	41.9	13	Van Dijk et al., 2013 Heberger, 2012	The Millennium Drought lasted 5–8 years (in some areas 10 years). Declines in rainfall and runoff led to widespread crop failures, livestock losses, dust storms, and bushfires.
39	Southwestern Europe, Turkey 2007–08	MED	01/07	01/09	42.3	1.7	36.3	15	August et al., 2008 Simsek and Cakmak, 2010	This drought had agricultural impacts over Turkey during a hot-dry summer. Also Cyprus and Greece were impacted, but with a lower degree of severity.
40	Argentina, Chile 2008–10	SSA	03/08	01/10	42.9	1.9	56.2	20	NASA EO (2009),Müller et al., 2014	Considered one of the top droughts in the last five decades over Southern America. It resulted in vegetation, soil, and crop impacts.
41	Horn of Africa 2008–10	EAF	08/08	08/10	45.3	1.8	44.5	16	Zaitchik et al., 2012 Masih et al., 2014 Nicholson, 2014	Due to prolonged low rainfall regimes, this drought pushed another drought (2011), but this time only over the easternmost part in the Horn of Africa.
42	Middle-East, Central Asia, India 2008–10	CAS SAS	03/08 06/09	09/09 08/10	30.2 27.3	1.8 1.8	54.2 38.8	16 15	USDA, 2008 Neena et al., 2011 Cook et al., 2016 FAO, 2017	Middle-East worst drought since decades: Iran, Iraq, Syria, and Middle-East reduced grain production, wheat production (-23%). Also Tajikistan was severely involved in 2009–10. India 2009 drought occurred during the summer monsoon season. Internal circulation and weather dynamics had the leading role for India.
43	Russian heatwave-drought 2010	NEE	07/10	07/12	32.3	1.3	34.4	13	Wegren, 2011, Trenberth and Fasullo, 2012 Russo et al., 2015	The Russian mega-heatwave in 2010 forced drought and food insecurity. Large tundra and forest fires.
44	Central U.S. 2011–13	CNA	09/11	09/13	47.0	1.9	48.5	18	Hoerling et al., 2014	Very scarce spring precipitation caused this drought with no early warning. A dry summer prolonged the drought conditions.
45	U.K., Central-Southern Europe 2011–13	MED	10/11	08/13	33.3	1.5	37.4	15	Bissolli et al., 2012	Drought in 2011 over U.K. and then southern Europe in spring 2012. Main causes: dry periods in 2010–12 and high-pressure conditions. Lot of impacts on crop yields, water supplies, waterways, and health.
46	Southern U.S., Mexico 2011–13	CAM	08/11	10/13	29.0	1.1	33.9	12	Seager et al., 2014 Brower et al., 2015	Drought in Southern U.S. and Mexico started in winter 2010 and went on in 2011. Possible drivers: La Niña event in the tropical Pacific ocean, sea surface temperature anomalies, negative North Atlantic Oscillation in winter 2010–11.
47	China spring-summer 2011	EAS	04/11	06/12	24.4	1.6	33.9	12	Lu et al., 2014	Spring drought in 2011 over China, defined as once-in-a-50-year drought over the Yangtze river basin and the southern region. Shortage of drinking water for people and livestock, tremendous losses in agriculture and shipping industry.
48	U.S. and California drought 2011–14	ENA WNA	05/12 05/12	06/13 04/14	21.4 31.1	1.5 1.3	33.2 35.4	13 13	Griffin and Anchukaitis, 2014 Seager et al., 2015 Otkin et al., 2016	Flash drought over Central and Northeastern U.S., with soil moisture conditions changing rapidly. This drought includes the 2011–14 California drought, an unusual drought spread over New Mexico and northern Mexico. It was driven by high temperatures and low (but not exceptionally low) rainfall.
49	East Australia 2013–16	SAU	01/13	08/16	58.0	1.3	45.4	15	ABC, 2013 Aus Gov (BOM), 2015	After the Millennium drought, in 2012–14 drought came back to Australia, especially over the East. It was due to long-term rainfall deficits. Also Queensland was hit.
50	South Africa 2015–16 (18)	SAF	02/15	12/16	43.8	1.9	54.4	19	Archer et al., 2017; Phys. Org. (2018) Masante et al., 2018 Yuan et al., 2018	This drought caused the Cape Town water crisis 2018, with reservoir volumes down to 19%. People collaborated to save water to avoid “day zero”. After an agricultural drought in 2017–18, South Africa declared the state of national disaster in March 2018 (lifted in June 2018)
51	Mediterranean 2015–16 (17)	MED	11/15	12/16	24.6	1.8	41.5	17	Van Lanen et al., 2016 Di Giuseppe et al., 2017 Garcia-Herrera et al., 2018	Drought started in 2016 due to low rainfall, especially in Southern Europe; it was prolonged by a summer heatwave over southern Europe in 2017, especially over Italy and Northern Africa (up to 48 °C).
52	Amazonia, central S-America 2015–16 (17)	AMZ CSA	10/15 04/16	12/16 12/16	35.8 12.7	2.4 1.4	49.7 47.8	16 12	Jiménez-Muñoz et al., 2016 Erfanian et al., 2017 Reliefweb, 2017	El Niño event in 2015–16 forced drought over the Amazon forest with an unprecedented warming in eastern Amazonia (western Amazonia was wet). Eco-hydrological consequences from the 2016 drought are more severe and extensive than the 2005 and 2010 droughts. Human factors potentially contributed to drought severity.