Download Status of climate change/variability studies and potential impacts of

Status of climate change/variability studies and
potential impacts of climate change/variability on
national and regional agriculture, rangelands,
forestry and fisheries in RA-II region
by
H. P. Das
Division of Agricultural Meteorology
India Meteorological Department
Major risks due to climate change
The following are the major risks in Asia apprehended from climate change:
•
The frequency of forest fires is expected to increase in boreal Asia.
•
Increased precipitation intensity, particularly during the summer monsoon,
could increase flood prone areas in temperate and tropical Asia. There is
a potential for drier conditions in arid and semi-arid Asia during summer,
which could lead to more severe droughts.
•
Crop production and aquaculture would be threatened by a combination
of thermal and water stresses, sea level rise, increased flooding, and
strong winds associated with intense tropical cyclones.
Present trend and variabilities in key climatic variables
Surface air temperature
Boreal Asia (Humid and •
cool-Continental type)
•
•
Arid and Semi-arid Asia
(Warm temperate type)
•
•
•
Temperate Asia
•
•
•
•
Tropical Asia
•
•
•
Increase of 2.9 0C/100 years (more pronounced during 1951-95)
Increase of 4.4 0C/100 years during the winter
Decreasing trend in Central Siberia
Increase of about 1.3 0C/100 years in the arid regions of China.
Increasing tendency is also observed in Middle East, Kazakhstan and
Pakistan
The highest value of 20 0C DTR is exprienced in this region
Increase of about 0.7 0C/50 years in Mangolia
Increasing tendency during winter but decreasing tendency in summer in
Northeast China
Decrease of 1-2 0C in parts of South east China
Warming trend in Japan during the past century
The warming trend in India, Pakistan, middle East, Vietnam (0.32 0C/30
years) Sri Lanka (0.30 0C/100 years)
Increasing trend in southern and central India in all seasons and over all of
India in the post-monsoon seasons.
DTR shows an increasing trend in all the seasons over most of Peninsular
India
Present trend and variabilities in key climatic variables
Precipitation
Boreal Asia where rainfall is 
highly variable on seasonal
and interannual as well as
spatial scales.

Arid and semi-arid region 
of Asia where rainfall is
considerably low but temporal
variability is quite high.


Mean annual precipitation in Russia suggests a decreasing
trend, particularly during 1951-1995, specially in warm years.
However, a decreasing trend of about 4.1 mm/month/100
years in Boreal Asia.
During the past 10-15 years, however, precipitation has
increased mostly during the summer-autumn period. As a
result of this increase in precipitation, water storage in a 1
mm soil layer has grown by 10-30 mm. The large upward
trend in soil moisture (of more than 1cm/10 years) have
created favourable condition for infiltration into ground
water. The levels of major acquifers have risen by 50-100 cm.
Mean annual precipitation shows an increasing trend during
the past 50 years in some countries in the northern part of this
region.
However, a decreasing trend in annual precipitation has been
observed in Kazakhstan during the period 1894-1997, but
increasing trends observed during spring, summer and
autumn.
In Pakistan, seven out of 10 states have shown increasing
tendency during summer season.
Precipitation
(Contd..)
Temperate Asia where the
East Asian monsoon greatly
influences temporal and spatial
variation in rainfall
Tropical Asia where hills and
mountain ranges cause striking
spatial variation in rainfall
• Summer rainfall seems to have declined over the period 197090 in Gobi, the number of days of heavy rainfall events has
dropped significantly.
• In China, annual precipitation has been decreasing since 1965.
This decrease has become serious since the 1980s.
• The summer monsoon is reported to be stronger in northern
China during globally warmer years, but drier condition have
prevailed over most of the monsoonal area during colder years.
• The annual mean rainfall in Sri Lanka is practically trendless,
positive trend in February and negative trends in June have
been reported.
• A long-term decreasing trend in rainfall in Thailand is reported.
• In Bangladesh, decadal departures were below long-term
averages until 1960, but afterwards they were above normal.
• In India, time series of summer monsoon rainfall have no
discernible trends but decadal departures are found above and
below the long-term averages alternatively for 3 consecutive
decades.
• Recent decades have exhibited an increase in extreme rainfall
events over northwest India during the summer monsoon. The
number of rainy days along the eastern coast has declined in the
past decade.
Status of extreme and severe weather systems
There is some evidence of increase in the intensity or frequency of some of extreme weather
events like heat waves, extratropical and tropical cyclones, prolonged dry spells, intense
rainfall, tornadoes, snow avalanches, thunder storms, dust storms etc on regional scales in
widely separated areas of Asia throughout the 20th century.
Boreal Asia
•
•
•
Increases in climate extremes in the western Siberia-Baikal region and eastern parts of
boreal Asia have been reported in recent decades.
Some mountains in Asia have permanent glaciers that have vacated large areas during the
past few decades, resulting in increases in glacial runoff. As a consequence, an increased
frequency of events such as mudflows and avalanches affecting human settlements has
occurred.
As mountain glaciers continue to disappear, the volume of summer runoff eventually will be
reduced as a result of loss of ice resources. Consequences for downstream agriculture,
which relies on this water for irrigation, will be unfavorable in some places. For example, low
and mid-lying parts of central Asia are likely to change gradually into more arid, interior
deserts.
Temperate Asia
•
•
In China, droughts in 1972, 1978, and 1997 have been recorded as the most serious and
extensive. A large number of severe floods also have occurred in China, predominately over
the middle and lower basins of the Yangtze (Changjiang), Huanghe, Huaihe and Haihe rivers.
In Japan, drought disasters are significantly more frequent during years following ENSO
warm events than in normal years.
Status of extreme and severe weather systems
(Contd..)
Tropical Asia
•
•
•
•
•
No identifiable variability in the number, frequency, or intensity of tropical cyclones or depressions
has been observed in the northern Indian Ocean cyclone region (Bay of Bengal and Arabian Sea)
over the past 100 years, although there was some evidence of decadal scale variations with a rising
trend during 1950-75 and a declining trend since that time.
No conclusive increasing or decreasing trends in time series data of flooded areas has been
noticed in various river basins of India and Bangladesh.
In India, Laos, the Philippines, and Vietnam drought disasters are more frequent during years
following ENSO events. At least half of the severe failures of the Indian summer monsoon since
1871 have occurred during El Niño years.
It is found that the 1891-1920 and 1961-80 periods witnessed frequent droughts while few droughts
occurred during 1930-1960 and 1980-2000. This suggests some kind of low frequency oscillation of
the monsoon system on the decadal scale.
There are also reports of an increase in thunderstorms over the land regions of tropical Asia.
Arid and Semi-arid Asia
•
•
•
•
Over arid and semi-arid regions of India there have been periods in the last decades of the
nineteenth century and first two decades of twentieth century when drought frequencies have been
markedly higher than in recent years, although individual recent droughts may have been intense
ones in some regions.
The frequency and severity of wild fires in grassland and rangelands in arid and semi-arid Asia
have increased in recent decades.
Coupled with the conversion of grazing lands to farming, the arid regions of India is undergoing an
aggravation of desertification through erosion of lands and aeolian shifting of soil particles. In
some locations, there has been a rise in water table with simultaneous increase of salinity and
deterioration of soil regime.
The variation of the aridity index line, computed by Penman method, over arid regions of India
reveals a possible spread of arid conditions in southeast direction.
Table 1
Possible changes in area-averaged surface air temperature over Asia and its sub-regions as a result of future
increases in greenhouse gases. Numbers in parenthesis are area-averaged changes when direct effects of
sulphate aerosols are included.
Temperature Change 0C)
2050s
2020s
2080s
Regions
Annual
Winter
Summer
Annual
Winter
Summer
Annual
Winter
Summer
Asia
1.58
(1.36)
1.71
(1.52)
1.45
(1.23)
3.14
(2.49)
3.43
(2.77)
2.87
(2.23)
4.61
(3.78)
5.07
(4.05)
4.23
(3.49)
Boreal
2.17
(1.88)
2.66
(2.21)
1.71
(1.47)
4.32
(3.52)
5.52
(4.46)
3.29
(2.83)
6.24
(5.30)
8.04
(6.83)
4.82
(4.24)
1.61
1.56
(1.55)
1.77
(1.49)
3.18
(2.69)
2.81
(2.61)
3.55
(2.59)
4.83
(4.15)
4.41
(3.78)
5.34
(4.36)
Arid/Semi-arid
Central
Asia
(1.47)
Tibet
1.77
(1.56)
1.90
(1.83)
1.62
(1.40)
3.38
(2.62)
3.55
(2.94)
3.19
(2.27)
5.04
(4.06)
5.39
(4.32)
4.69
(3.73)
Temperate
1.49
(1.19)
1.74
(1.50)
1.23
(0.99)
2.86
(2.10)
3.26
(2.40)
2.48
(1.72)
4.34
(3.31)
5.11
(3.83)
3.67
(2.77)
Tropical
South Asia
1.36
(1.06)
1.62
(1.19)
1.13
(0.97)
2.69
(1.92)
3.25
(2.08)
2.19
(1.81)
3.84
(2.98)
4.52
(3.25)
3.20
(2.67)
SE Asia
1.05
(0.96)
1.12
(0.94)
1.01
(0.96)
2.15
(1.72)
2.28
(1.73)
2.01
(1.61)
3.03
(2.49)
3.23
(2.51)
2.82
(2.34)
Table 3
Precipitation
Precipitation Change (0C)
2050s
2020s
2080s
Regions
Annual
Winter
Summer
Annual
Winter
Summer
Annual
Winter
Summer
Asia
3.6
(2.3)
5.6
(4.3)
2.4
(1.8)
7.1
(2.9)
10.9
(6.5)
4.1
(1.5)
11.3
(7.0)
18.0
(12.1)
5.5
(3.5)
Boreal
6.1
(6.7)
11.1
(10.7)
2.6
(3.3)
12.8
(12.0)
23.8
(19.7)
5.1
(7.1)
20.7
(18.9)
39.5
(31.5)
7.7
(10.3)
Arid/Semi-arid
Central Asia
1.3
(1.1)
3.0
(2.7)
-2.1
(5.9)
1.3
(0.6)
6.9
(1.4)
-2.3
(0.7)
-1.3
(-3.6)
6.9
(1.0)
-4.0
(-1.8)
Tibet
5.9
(3.4)
8.9
(7.4)
4.4
(1.7)
9.0
(7.5)
19.2
(14.8)
4.7
(1.7)
12.8
(11.5)
25.6
(18.8)
5.7
(3.8)
Temperate
3.9
(0.9)
4.2
(0.4)
3.7
(1.2)
7.9
(1.3)
13.3
(4.3)
5.4
(0.7)
10.9
(4.8)
20.1
(7.1)
7.8
(3.1)
Tropical
South Asia
2.9
(1.0)
2.7
(-10.1)
2.5
(2.8)
6.8
(-2.4)
-2.1
(-14.8)
6.6
(0.1)
11.0
(-0.1)
5.3
(-11.2)
7.9
(2.5)
SE Asia
2.4
(1.7)
1.4
(3.3)
2.1
(1.2)
4.6
(1.0)
3.5
(2.9)
3.4
(2.6)
8.5
(5.1)
7.3
(5.9)
6.1
(4.9)
Extreme events – Future scenario
•
Recent observations suggest that there is no appreciable long term variation in the total number of
tropical cyclones observed in the north Indian, southwest Indian, and southwest Pacific Oceans east
of 160 0E .
•
The frequency of typhoons and the total number of tropical storms and typhoons has been more
variable since about 1980. Some studies suggest an increase in tropical storm intensities with carbon
dioxide (CO2) induced warming.
•
Some of the most pronounced year-to-year variability in climate features in many parts of Asia has
been linked to ENSO.
•
Future seasonal precipitation extremes associated with a given ENSO event are likely to be more
intense in the tropical Indian Ocean region; anomalously wet areas could become wetter, and
anomalously dry areas could become drier during ENSO events.
•
The intensity of extreme rainfall events is projected to be higher in a warmer atmosphere, suggesting
a decrease in return period for extreme precipitation events and the possibility of more frequent
flash floods in parts of India Nepal, and Bangladesh.
•
No significant change is found in the number and intensity of monsoon depressions (which are largely
responsible for the observed interannual variability of rainfall in the central plains of India) in the
Bay of Bengal in a warmer climate.
Impact of climate variability and change on agriculture
Boreal Asia where climate
change could have serious
effects on climate
dependant sectors such as
agriculture, forestry, and
water resources
•
Climate change and human activities, for example, may
influence the levels of the Caspian and Aral Seas, with
implications for the vulnerability of natural and social
systems.
•
The increase in surface temperature will have favorable
effects on agriculture in the northernmost regions of
Asia, and a general northward shift of crop zones is
expected. However, as much as a 30% decrease in
cereal production from the main agriculture regions of
boreal Asia by 2050 has been projected.
•
A decrease in agriculture productivity of about 20% also
is suggested in southwestern Siberia.
•
Forest ecosystems in boreal Asia could suffer from
floods and increased volume of runoff, as well as
melting of permafrost regions.
•
Model based assessments suggest that significant
northward shifts (up to 400 km) in natural forest zones
are likely in the next 50 years.
•
There also is growing anxiety that significant increases
in ultraviolet radiation, as observed in recent years,
could have serious implications for ecosystems along
the Arctic shore of Siberia .
Impact of climate variability and change on agriculture
(Contd…)
Arid and semi-arid Asia
where the climate limits
the portion of land that
presently is available for
agriculture and livestock
production. Croplands in
many of the countries in
the region are irrigated
because rainfall is low and
highly variable.
•
The agriculture sector here is potentially highly
vulnerable to climate change because of degradation of
the limited arable land.
•
Almost two thirds of domestic livestock are supported
on rangelands, although in some countries a significant
share of animal fodder also comes from crop residues.
•
The combination of elevated temperature and
decreased precipitation in arid and semi-arid
rangelands could cause a manifold increase in potential
evapotranspiration, leading to severe water stress
conditions.
•
Many desert organisms are near their limits of
temperature tolerance.
•
Because of the current marginality of soil water and
nutrient reserves, some ecosystems in semi-arid
regions may be among the first to show the effects of
climate change. Climate change has the potential to
exacerbate the loss of biodiversity in this region.
Impact of climate variability and change on agriculture
(Contd…)
Temperate Asia where the
major impacts of global
warming will be large
northward shifts of
subtropical crop areas.
•
Large increases in surface runoff leading to soil erosion
and degradation, frequent waterlogging in the south,
and spring droughts in the north ultimately will affect
agriculture productivity
•
The volume of runoff from glaciers in central Asia may
increase three fold by 2050.
•
Permafrost in northeast China is expected to disappear
if temperatures increase by 2 0C or more. The northern
part of China would be most vulnerable to hydrological
impacts of climate change; future population growth
and economic development here may exacerbate
seriously the existing water shortage.
•
Deltaic coasts in China would face severe problems
from sea level rise.
•
Sea-level rise also will expand the flood-prone area and
exacerbate beach erosion in Japan.
Impact of climate variability and change on agriculture
(Contd…)
Tropical
Asia
where
Agricultural productivity is
sensitive not only to
temperature increases but
also to changes in the
nature and characteristics
of monsoon.
•
In Bangladesh, the impact of climate change on high
yield rice varieties was studied and found that the
detrimental effect of temperature rise more than offset
the positive effect of increased CO2 level on rice.
•
In India it was found that higher temperatures and
reduced radiation associated with increased cloudiness
caused spikelet sterility and reduced yields to such an
extent that any increase in dry matter production as a
result of CO2 fertilization proved to be no advantage in
grain productivity.
•
Rice yields in east Java of Indonesia could decline by
1% annually as a result of increases in temperature.
•
In tropical Asia, although wheat crops are likely to be
sensitive to an increase in maximum temperature, rice
crop would be vulnerable to an increase in minimum
temperature.
•
The adverse impacts of likely water shortage on wheat
productivity in India could be minimized to a certain
extent under elevated CO2 levels; these impacts,
however, would be largely maintained for rice crops,
resulting in a net decline in rice yields.
Table 4
Yield impact of selected climate change studies for rice in Tropical Asia.
Geographic Scope
Yield Impact (%)
Bangladesh
-6 to +8
Bangladesh
+10
Bangladesh
-9 to +14
Thailand
-17 to +6
Thailand sites
-5 to +8
Thailand
-12 to +9
Philippines
-21 to +12
Philippines
decrease
Philippines
-14 to +14
Indonesia
-3
Indonesia
approx. –4
Indonesia
+6 to +23
Malaysia
-22 to -12
Malaysia
+2 to +27
Malaysia
-14 to +22
Table 5
Increase in yield (%) of different cultivars under modified climate of northwest India
Cultivar (Station)
Rainfed
Irrigated
S-II
S-III
S-II
S-III
WH542(Hisar)
37
30
27
23
HD2329(Ludhiana)
31
22
16
12
HD2285(Delhi)
29
24
22
19
Sonalika(Pantnagar)
34
27
22
18
Raj3765(Jaipur)
36
29
28
22
S-I :current climates
S-II: Tmax + 1.00C, Tmin+1.50C, 2 x CO2
S-III: Tmax + 2.00C, Tmin+2.50C, 2 x CO2
Table 6
Possible impacts due to different climate scenarios in 2050s (billion Yuan)
Region
North
Northeast
East
Central
South
Southwest
Northwest
Plateau
Total
Changes of net revenue
E4-gg
CG-gg
CG-gs
H2-gs
H2-gx
(3.10C, 10.4%)
(4.70C, 4.7%)
(3.20C, -6.2%)
(1.30C, 0.2%)
(2.50C, 10.4%)
8.820
-57.307
-57.611
19.122
18.133
(18.16)
(-117.91)
(-118.62)
(39.37)
(37.33)
-1.213
-4.298
-3.635
-0.340
-1.075
(-8.61)
(-30.50)
(-25.9)
(-2.41)
(-7.63)
4.859
-8.333
-9.520
13.306
9.192
(19.25)
(-33.01)
(-37.71)
(52.71)
(36.41)
1.190
-3.289
-4.653
1.548
1.883
(13.89)
(-38.36)
(-54.27)
(18.05)
(21.97)
1.8761
0.633
1.316
2.087
2.406
(15.76)
(5.31)
(11.05)
(17.53)
(20.20)
0.275
-7.386
-8.915
0.416
-0.628
(1.81)
(-48.54)
(-58.58)
(2.73)
(-4.13)
-0.271
-8.561
-6.559
0.678
0.794
(-4.27)
(-134.98)
(-103.36)
(10.68)
(12.51)
0.007
-0.018
-0.011
0.004
0.0138
(6.97)
(-17.36)
(-10.77)
(4.29)
(13.49)
15.543
-88.559
-89.587
36.821
30.718
(11.95)
(-68.09)
(-68.88)
(28.31)
(23.62)
Impact of climate variability and change on forestry
Impact on boreal forests
•
Climate change may affect the biodiversity in boreal forests of Asia through a
myriad of processes and effects like local mortality of boreal species and
replacement by northern hardwoods or prairies, migration of boreal species
northward and coastward, increased probability of fire; increased or decreased
soil nutrients availability, increased emissions of green house gases particularly
methane from wetlands etc.
•
Major alterations in vegetation could be expected, specially in the mountains of
the northern boreals subzones and the
subarctic forest – tundra ecotone in
northeast Siberia.
•
In the middle and southern boreals subzones, vegetation changes may be more
limited because of more resistant species interaction in the forest communities
of the continental area and the isolated islands of the Kuril, Shantar and
Kommander groups.
(Contd..)
Impact on temperate forests
•
Studies on projected impacts of climate change suggest that northeast China
may be deprived of the conifer forests and its habitat and broad leaved forests
in east China may shift northward by approximately 3
0
of latitude. These
results are based on a 2 0C increase in annual mean temperature and a 20%
increase in annual precipitation.
•
Although the area of potential distribution of temperate forests in Temperate
Asia is to a large extent, cleared and used for intensive agriculture, global
warming can be considered to trigger structural changes in remaining
temperate forests.
The nature and magnitude of these changes depend on
associated changes in water availability, as well as in water use efficiency.
•
Shifts in temperature and precipitation in temperate rangelands may result in
altered growing seasons and boundary shifts among grasslands, forests and
shrublands.
(Contd..)
Impact on tropical forests
•
Results of research from Thailand suggest that climate change would
have a profound effect on the future distribution, productivity, and
health of Thailand’s forests. The area of subtropical forest could decline
from the current 50 % to either 20 % or 12 % of Thailand’s total forest
cover (depending on the model used), whereas the area of tropical
forests could increase from 45 % to 80 % of total forest cover.
•
A decrease in tropical rainforest of 2-11 % and an increase in tropical
dry forest of 7-8 % in Sri Lanka.
•
A projected depletion of soil moisture would likely cause teak
productivity to decline from 5.40 m3/ha to 5.07 m3/ha in India.
The
productivity of moist deciduous forests also could decline from 1.8
m3/ha to 1.5 m3/ha.
(Contd..)
Impact on Arid and Semi-Arid rangeland
•
With an increase in temperature of 2-3 0C combined with reduced precipitation as projected
for the future in the semi-arid and arid regions of Asia, grassland productivity is expected
to decrease by as much as 40-90 %.
•
Rangelands in Nepal also have been subjected to degradation in recent years. Climate
change is likely to represent an additional stress to rapid social change in many of Asia’s
rangelands.
•
Shifts in temporal biomass patterns due to changed climate have potentially significant
implications for grazing management.
•
Forest fires alter the structure of vegetation and affect nutrient cycling. By making nitrogen
and other nutrients more available to soil microorganisms, fire may result in enhanced
emissions of nitrous oxide (N2O) from soil.
Effect on Fisheries
•
Climate change impacts on fish species generally will be positive through faster
growth, low winter mortality rates, reduced ice cover, and reduced energy costs
as a result of expanded regions of warmer water. Cultivation of warm water
species also may expand. Warming will require greater attention to possible
oxygen depletion, fish diseases, and introduction of unwanted species.
•
For marine fisheries, slight changes in environmental variables such as
temperature, salinity, wind speed and direction, ocean currents, strength of
upwelling, and predators – can sharply alter the abundance of fish population.
Rises in sea level also may cause saline water fronts to penetrate further inland,
which could increase the habitat of brackish – water fisheries.
Coastal
inundation also could damage the aquaculture industry.
•
Fisheries at higher elevations may be particularly affected by lower oxygen
availability resulting from increases in temperature. In the plains, the timing
and amount of precipitation may affect the migration of fish species from the
river to the flood plains for spawning, dispersal and growth. If the magnitude
and extent of floods increase, more flood control projects would further deplete
flood plain fisheries.
Effect on Fisheries
(Contd..)
•
Marine productivity is greatly affected by temperature changes that control
plankton shift, such as seasonal shifting of sardine in the sea of Japan and
induced during the cyclic occurrence of the ENSO in low latitudes. The impact
of global warming on fisheries will depend on the complicated food chain,
which would be disturbed by sea level rise, changes in ocean currents, and
alteration of mixing layer thickness.
•
The rise in the SST will shift the southern limit of salmon species further to the
north. It is also suggested that the Sea of Japan bottom water will become
anoxic within a few hundred years; a decreased oxygen supply will lead to
major losses in biological productivity in deep waters.
•
Increased frequency of El-Nino events, which are likely in the warmer
atmosphere, could lead to measurable declines in plankton biomass and fish
larvae abundance in coastal waters of south and southeast Asia. Such declines
in lower levels of the food chain will have negative impacts on fisheries in Asia.