Drought

1. Heat waves, drought, dust
 Several thousand people die each year
worldwide from heat stress.
 Most deaths in North America occur in inner
cities in the southeastern US.
 Severe urban pollution may be a contributing
factor.
Heat stress

2. Heat waves and heat
disorders
At temperatures above the body’s core
temperature (37°C) heat must be dissipated.
~90% of heat loss occurs through skin; sweating
becomes less effective at high RH (hence the
increase in “apparent temperature”. If heat gain
exceeds heat loss, body core temperature rises,
and heat disorders occur.
Sunburn can retard the body’s ability to shed
heat, and may increase the severity of the heat
disorder.

3. Human tolerance of high temperatures
Data: NASA
40 45 50 55 60 65 70 75 80 85 90 95 100
Relative humidity (%)
Air
temperature
(°C)
extreme danger
danger
Heat Index chart:
apparent temperature
core

4. Heat disorders and apparent temperature
>50°C: heatstroke/sunstroke highly likely with
continued exposure
40-50°: sunstroke, heat cramps likely, and
heatstroke possible with prolonged exposure
and/or physical activity
35-39°: sunstroke, heat cramps and heatstroke
possible with prolonged exposure and/or physical
activity
30-34°: fatigue possible with prolonged exposure
and/or physical activity
NB: heat disorders increase with age - individual @ :
20yr - heat cramps; 40yr - heat exhaustion; >60yr - heat stroke

5. Heat mortality
Three times
as many
people die on
extremely
hot days as
on normal
summer days

6. Heat wave in Europe, summer 2003
Fatalities
France 14 800
Italy 4 000
Germany 3 500
Spain 2 000
Portugal 1 300
U.K. 900
Holland 500
extreme
strong
moderate
slight
comfortable
Heat Load
Heat load, Aug. 8, 2003 @ 1300h

7. Heat waves and climate
change
In the summer of 2003 Germany recorded mean
temperatures >3°C above the mean for the
period 1961-1990;
 Was this just a 1 in 500 year extreme event?
 Or was it a foretaste of the “x2 CO2”
summers of the mid-21st century?

8. Predicted winter and summer temperature changes (°C) in
California -Nevada, for AD 2070-2099 compared to AD 1961-1990
CO2 by AD 2100: ~550 ppm ~970 ppm
GCM: PCM Hadley PCM Hadley
+10
+5
0
+10
+5
0

9. Predicted heat-wave days in California*
1961-90 2020-49 2070-99
CO2 (ppm) ~320 ~550 ~970 ~550 ~970
Los Angeles 12 24 36 47 95
El Centro 162 176 180 197 218
*Predictions based on the Hadley GCM

10. Photos: Munich Re, 2004
Heat waves,
drought and
wildfires
frequently co-occur
dessicated sunflowers,
France, 2003
wildfires, Portugal, 2003

11. Drought:
“a protracted period of
deficient precipitation
resulting in extensive
damage to crops,
resulting in loss of
yield”
Hazard profile:
 slow onset
 prolonged duration
 widespread

12. Drought and aridity
The social and economic costs of
drought are greatest in climates
close to the margins of agricultural
or pastoral production (e.g. in
subhumid areas* rather than
hyperarid or perhumid areas)

13. hyperarid arid semi-arid dry subhumid
humid…………..perhumid
8% 12% 18% 10 % 52%
AI 0.05 0.20 0.50 0.65
Aridity Index:
= P/PET [UNEP,
1992] and
drought risk

14. Drought: some early operational
definitions
• Great Britain (1936): 15 consecutive days with daily
precipitation totals of less than .25 mm
• United States (1942): less than 2.5 mm of rainfall in
48 hours
• India (1960): actual seasonal rainfall deficient by
more than twice the mean deviation
• Bali (1964): a period of six days without rain
• Libya (1964): annual rainfall less than 180 mm
Note: locally-specific criteria

15. Drought indices
• Standardized Precipitation Index
(a probabilistic index based on rainfall amount
compared to normals for the same period)
• Palmer Drought Severity Index
(based principally on antecedent rainfall and
temperature)
• Palmer Crop Moisture Index
(based on measured soil moisture vs. normal
amount)

16. Current SPI and PDSI
maps (North America)

17. Drought - damages
Direct
 loss of income
 social dislocation
 famine/malnutrition/death
Indirect
 loss of rural and urban revenues
 fire hazard, loss of water access

18. Drought climatology
 Temperate climates - influence of blocking
highs in zone of westerlies
 Seasonal tropical climates - influence of
ITCZ position on monsoon penetration
 Humid tropical climates - influence of El
Niño - Southern Oscillation

19. Storm tracks, blocking highs and
drought in the Canadian Prairies
zonal flow:
no drought
drought in
Alberta
drought in
Manitoba
drought
throughout

20. Aridity Index:
Canadian prairie provinces
Medicine Hat
Alberta
Sask.
Manitoba
Winnipeg

21. The 2000-2002
drought in the
Prairie provinces
AD 2001
AD 2002
Annual precipitation

22. Consequences of the 2000 - 2002
drought
 “the persistent dryness, coupled with record high temperatures and
grasshopper infestations, means many farmers will be bowing out of
the 2002 crop season early” Edmonton Journal, July 26, 2002
 Alberta provincial government announces $324 M in drought aid;
Saskatchewan to follow Alberta’s lead;
 Farmers sell off beef herds, accused of dumping beef in BC;
 Federal government arranges to pay for hay shipments from Ontario,
then stops shipment because of potential cereal beetle infestation.
Drought loss of farm income

23. The drought of the 1930’s:
the Dust Bowl

24. DUST BOWL
Precursors
 x10 increase in population in OK,TX,AK from 1860 -
1920.
 Deep ploughing and wheat monoculture destroyed
soil structure and increased soil erosion potential
Drought (1931-1940)
 world economic slump in 1930’s; virtually no federal
funds for prairie farmers
 economic disaster - outmigration of “Okies”

25. Grapes of Wrath
“And then the dispossessed were drawn west - from
Kansas, Oklahoma, Texas, New Mexico: from
Nevada and Arkansas, families, tribes, dusted out,
tractored out. Car-loads, caravans, homeless and
hungry, . . . they streamed over the mountains,
hungry and restless . . . Scurrying to find work to
do, . . Anything, any burden for food. The kids are
hungry. We got no place to live. Like ants scurrying
for work, for food, and most of all for land”
John Steinbeck (1939)
Drought loss of farm income social dislocation

26. Were the 1930’s as bad as it
gets?
Drought incidence, Medicine Hat, Alberta (AD1900-
1996)
Sauchyn et al., 2002, Géographie physique et Quaternaire 56, 247-259.

27. The Dust Bowl:
exacerbating factors
 overgrazing
 cropping of marginal soils
 soil erosion
-------------------------------------------
Drought effects may also be
magnified in areas of political strife
and severe wildfires

28. Prairie climate: reconstruction from tree ring analysis
Lodgepole pine:
Medicine Hat, AB
Sauchyn et al., 2002, Géographie physique et Quaternaire 56, 247-259.

29. Prairie climate: reconstruction from analysis of lake sediments
fresh
P PET
saline
, Alberta
diatoms

30. Future desertification?
Aridity index: 2000
Canadian GCM
UK GCM
?
?
Sauchyn et al., 2002,
Géographie physique
et Quaternaire 56, 247-
259.

31. Drought in monsoon climates:
the Sahel
Inter-Tropical Front /
Inter-Tropical Convergence Zone
Population density
(orange >25 people km-2)
Source: www.mapjourney.com/sahel/

32. Drought in
monsoon
climates:
the Sahel
Vegetation
(max.)
Rainfall
1984 1998
500 km
20°N

33. Northward penetration of the
monsoon, West Africa (1951-1973)

34. Changing rainfall patterns in the Sahel region

36. Hypotheses to explain Sahelian
drought
“Climatological” - northward penetration of ITCZ controlled by
variations in atmospheric temperature in northern tropics, due to:
1. SST anomalies in northeastern Atlantic linked to general circulation
(especially El Niño/La Niña), or
2. Industrial pollution (particularly SO2 aerosols) from N.America,
Europe and Asia (intense drought of 1970-85).
“Anthropogenic” - changes in vegetation and surface albedo caused by
varying land-use result in changes in regional climate.
All of these may be influenced by global warming

37. vegetation
Rapp’s albedo
feedback model
rainfall
grazers

38. The evidence
for Rapp’s
model

39. SAHEL
Drought
5M people affected; >200K died from
malnutrition and associated diseases
Livestock herds decimated (80% died)
Loss of livestock * loss of wealth *
massive social dislocation and
emigration to urban areas

40. ENSO and drought in western Pacific
(Indonesia and N. Australia)

41. July, 1997
(El Niño)
July, 1998
(La Niña)
Rainfall relative to
historical records

42. Effects of 1997-98 drought in Indonesia
Agricultural production:
20 - 30% reduction of rice crop in eastern
Indonesia (parts of Kalimantan, Sulawesi and
Irian Jaya. Markedly lower yam production in
Irian Jaya.
In some villages in the latter 20-30% of
people died from malnutrition; 95% incidence
of malaria reported. Conditions not as severe
in western Indonesia (e.g. rice production only
dropped 6% in Sumatra)

43. Wind erosion and deposition:
abandoned farm, Kansas, 1934

44. Dust storm during the 1930’s drought
in the southern Great Plains

45. Dust storm, E. Australia, 2002

46. October 23, 2002 dust storm (Brisbane, QLD)
Chan et al., 2005. Water, Air, & Soil Pollution, 164, 329-348.
Event lasted 16 h
max conc. >800 µg m-3

47. Asian dust storms have been blamed
for increased mortality in urban areas in
Taiwan and South Korea. But is aeolian
dust a significant hazard to human
health?
Test case: a non-industrial area near
the source
Meng, Z. and Lu, B. 2007.
“Dust events as a risk factor for daily hospitalization for
respiratory and cardiovascular diseases in Minqin, China.”
Atmospheric Environment 41, 7048-7058.

48. Minqin, China