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Argentine Pampas Climate, Forecasting, and Social Implications

By Ivan Ramirez

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I. Introduction

The Pampas region of Argentina is one of the most highly productive agricultural areas in

South America and spans well over 75 million hectares of land of which 25% is

cultivated (see Figure 2: light green indicates cultivated land) (Mechoso et al., 2001;

Boulanger et al., 2005). Located in the temperate zone of central and northeastern

Argentina (See Figure 1), the Pampas are characteristically flat grasslands and plains that

are generally fertile. (Hammond World Atlas, 2000; Republica Argentina, 2006).

Agriculture that is mainly rainfed is an important livelihood for the local people and

contributes to ~51% of exports and ~12% of GDP in Argentina (University of Miami,

2006). The agricultural sector has been increasing since the 1980s, and in the areas near

Buenos Aires, agriculture grew by ~40% from 1988 to 1993 (Mechoso et al., 2001).

Wheat, soybean, and maize are the major crops grown in the region and account for 90%

of the land allocated for farming (Jones et al., 2000).

Figure 2. Map of Pampas and agricultural area.

Source: Republica de Argentina

For both figures.

Figure 1. Map of Argentina and Pampas

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Climate in the Pampas is generally subhumid and dominated by mid-latitude circulations

from the South Pacific Ocean. Rainfall is prevalent in the austral summer and autumn,

and markedly influenced by the interannual variability pattern known as El Niño/

Southern Oscillation (ENSO) CLIVAR, 1999; Barros, 2000; University of Miami, 2006).

ENSO is a major concern for agricultural producers and the general population in the

region. Both the warm phase (El Niño) and cold phase (La Niña) are associated with

rainfall anomalies that create favorable and unfavorable conditions for crops in the

Pampas (Hansen et al., 2002; Podesta et al., 1999; Messina, Loustau, 2002). However, El

Niño does produce a strong climate signal that allows for some degree of predictability

and the possibility for incorporation of climate information into decision-making schemes

(Glantz, 2001).

This document presents the different scales of climate in the Argentine Pampas and

climate change in the region, climate forecasting capabilities for the region as well

climate information available, and the social implications of climate information. The

Argentine Pampas were chosen because the region exhibits a strong El Nino signal and

the information was available. The methodology is to conduct a literature review from

various leading authors, institutional reports from NCAR, IRI, and other organizations,

governmental websites, and utilize information from the CRED reports.

Following this introduction is a brief discussion of the general climate in the Pampas,

short-term forecasting, seasonality, and its applications in the region. The third section is

similar to the previous, but more extensive since it will be discussing the interannual

variability in the region, which strongly impacts the region. The fourth section is the

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interdecadal and multi-decadal variability in the region and discusses 20th

century

observations. The fifth section is climate change in the region, trends observed, future

projections and impacts, and mitigation/adaptation activities in the region. The final

section is the conclusions.

II. General Climate in the Pampas

The Pampas region is strongly influenced by mid-latitude circulations exerted from the

Tropical Pacific Ocean and affected by sea surface temperatures (SST) in the Southwest

Atlantic Ocean. Intra-seasonally, the South Atlantic Convergence Zone (SACZ)

dominates the austral summer from December to March (CLIVAR, 1999; Barros, 2000;

University of Miami, 2006). Via large-scale atmospheric circulations, the SACZ

teleconnects with the Atlantic Inter Tropical Convergence Zone when the South

American Monsoon (SAMS) extends southeastward along the northeastern boundary of

the Plata Basin (Mechoso et al., 2001; Boulanger et al., 2005). Local heat fluxes and

orographic lifting are important for the large-scale circulations associated with the SACZ

(Nogués-Paegle & Mo, 1997). The Andes Mountains in northern South America act as a

barrier and deflect low-level airflow, bringing moisture to southeastern South America

(Mechoso et al., 2001; Boulanger et al., 2005). However some studies suggest that the

South Pacific Convergence Zone may affect the SACZ, and that the Andes may not be as

important to upper-level flow associated with the SACZ (CLIVAR, 1999).

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Rainfall is generally found year-round in central and eastern Argentina, but it is markedly

seasonal (IRI, 2001). The maximum rainfall amounts normally occur in March and April

and again in October and November, while rainfall minimums occur in July through

September, the austral winter. Increases in rainfall during the summer are likely

attributable to a weaker SACZ and rainfall in the region and in South America are

generally correlated with SSTs in the Tropical Pacific Ocean (CLIVAR, 1999; Barros &

Silvestri, 2002).

Although farmers in the Pampas have benefited from rich soils, diffusion of technology,

and favorable precipitation trends--at least in the last 30 years, they remain vulnerable to

extreme weather events and climate variability due to their dependency on rainfall. In

addition, they face agriculture and economic uncertainties. The government does not

provide subsidies and commodity prices have fallen. However the potential to minimize

risks and optimize gains does exist in the region. There are sufficient climate records as

well as agricultural databases available. Several institutional collaborations are currently

in development for risk management through the use of climate information (Podesta et

al., 2002). Also available are many types of climate information sources such as

Argentina’s National Meteorological Service (METEOFA), which seems to be very

popular. Another popular source is the Instituto Nacional de Technologia Agropecuaria

(INTA), a private company that serves the agricultural industry and its members with

information on technology, development, and economics and makes available climate

forecasts (INTA, 2006). Several farmers that support INTA refer to periodic meetings in

which climate information is disbursed (CRED, 2006). One particular meeting that seems

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to be popular is regularly organized by Stella Carballo, who is an accountant by training,

and Dr. Sierra, a Professor of Meteorology at the University of Buenos Aires’ School of

Agronomy (Podesta, in person). One optimal use of the forecast is to use daily weather to

adjust planting dates and avoid water stress. Another beneficial use is related to

predicting extreme events, a wet period or dry period (usually related to ENSO) could

help to adjust suitable to either take advantage of the expected weather and climate.

However, while Argentine farmers do seek out climate information, the use of the

information is not generally maximized or even used. There exist many challenges in

using climate information. Firstly, climate itself is inherently uncertain and thus, there are

many uncertainties in the climate information provided. Farmers wish to have more

deterministic forecasts and forecasts with greater confidence. One event of bad forecast

can have a detrimental effect on the farmer’s trust of forecasts. Thirdly, the climate

information may not be communicated correctly or not suited for the end user’s needs.

Therefore, it is important to understand how the end user’s needs, how he/she perceives

the climate forecast, and the beliefs and/or constraints he/she has. For example, in a

recent CRED study (2006) that examined farmers’ perceptions in the Argentine Pampas,

the preliminary results show that farmers do seek climate information, but are not willing

to modify their planting schemes until a concrete event, which confirmed the forecast was

observed. Farmers tend to be risk averse, and unwilling to gamble, as many farmers say.

(Jones et al., 2002; Hansen et al., 2004).

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III. Interannual Variability

The central and eastern parts of Argentina exhibit one of the strongest teleconnections to

El Nino, the warm phase of ENSO (Podesta et al.2002; Bert et al., 2005; Berri et al.,

2005). ENSO has a cycle of 3 to 7 years, and during its warm phase, warm water from

the western Tropical Pacific Ocean shifts to the central and eastern Tropical Pacific

Ocean. The equatorial sea surface temperature gradient decreases, easterly winds weaken,

and atmospheric surface pressure decreases in the eastern Pacific Ocean. As a result, a

positive feedback occurs and convective activity and rainfall move eastward. See Figure

3 for a schematic of SST changes in the tropical Pacific during El Nino. In the cold phase

La Niña, the opposite occurs and there is a strengthening of easterly winds and opposite

anomalies (Goddard et al., 2001). Barros & Silvestri (2002) suggest that the ENSO

pattern is also influenced by SST variability in the South Central Pacific Ocean.

During El Nino years in the Pampas, the austral spring and summer are likely to

experience higher median rainfall amounts and are more pronounced in November and

December, a crucial time for planting in the Pampas. See Figure 4 for climate anomalies

during El Nino and La Nina. In the wintertime, warming is persistent and more intense in

El Nino years (Rusticcuci & Vargas, 2002). This is extremely important for farmers as

they already face a drier period in this time of the year. However, El Nino events in the

Pampas are generally variable. La Nina, the cold phase of ENSO, produces the likelihood

of reduced median rainfall in the region, is less pronounced, and has a narrower range of

anomalies. Positive rainfall anomalies occur from November to February in El Nino

years and negative rainfall anomalies occur from July to December in La Nina years

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(Mechoso et al., 2001; Barros & Silvestri, 2002; Rusticcuci & Vargas, 2002; University

of Miami, 2006). However, a CLIVAR study indicated that negative rainfall anomalies

were more pronounced during November and December of La Nina years than the

positive rainfall anomalies during El Nino years (Baethgen, 1999).

In a study by Coelho et al. (2002), it was shown that SST anomalies over the central

Equatorial Pacific, between 100°W - 150°W, are strongly connected to rainfall in South

America during El Nino; in contrast, during La Nina, the central Pacific area around

180°W, seems to be the most important influence on rainfall. However, Barros &

Silvestri (2002) found that rainfall in southern South America is not linearly related to

SSTs in the El Nino regions in austral spring. In 1997/1998, the strongest El Nino of the

20th

century was experienced and record rainfall amounts and several flood events were

observed in the Pampas (IRI, 2001).

Fig. 3 Schematic of Sea Surface Temperature Changes in the tropical Pacific Ocean during El Niño

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Figure 4. Anomalies exhibited during El Nino (warm)

Source: Climagro

Figure 5. Anomalies exhibited during La Nina (cold)

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ENSO patterns are correlated with crops in the Pampas, and therefore predicting or

understanding this climatic phenomenon is important for the region. The clearest

association is found in maize yields, which have a tendency to be higher during El Nino

events and lower during La Ninas (Podesta et al., 1999). ENSO partly explains these

outcomes, but ENSO also happens to coincide with the growing season for maize (Jones

et al., 2000). Soybean, the most important summer crop, is also associated with ENSO,

significantly with the cold phase, but varies between regions (Berri et al., 1999). Lower

rainfall results in lower yields, but higher rainfall amounts do not increase yields. This is

possibly due to water minimums that are satisfied and yield the maximum outputs. In

recent years there has been an increasing trend towards monoculture of soybeans because

of its lower input costs and stable yields; however, monoculture is not sustainable and

there is much concern (Bert et al., 2005). Wheat is another crop with some ties to El

Nino, particularly in the southern Pampas and during the month of November, a good

month for rains (Podesta et al., 1999).

Climate information that is used effectively can enhance agricultural management and

reduce vulnerability in the Pampas (Bert et al., 2005). ENSO is an important signal in the

region and can be exploited for predictability. In addition to crop correlations, ENSO is

also strongly associated with streamflow in El Nino years (IRI, 2001). In a study by Berri

et al. (2005), they found that the forecasts issued by the Climate Outlook Forum (COF),

were potentially better than the climatology for the region; a strong El Nino in 1997/1998

followed by La Nina until 2001, allowed for good skill. When compared with IRI

forecasts, IRI forecasts showed a slightly better result than the COFs, and did not add

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skill to IRI. The Climate Outlook Forum forecasts for Southeast Southern America,

which began in 1997 in Uruguay, was an integration of atmospheric models, physically

based statistical model, diagnostic analysis, and published literature on climate

variability. Until that time, IRI was the only source for seasonal forecast in the region

(Berri et al., 2005).

IV. Multi-decadal Variability

There is some evidence of inter-decadal variability in the region and some studies posit

that a multi-decadal pattern may also be evident. A precipitation increase has been

observed in the last 30 years that coincides with streamflow increases in the region

(Rusticucci & Penalba, 2001; University of Miami, 2006). The Argentine Delegation to

CLIVAR in 1999 issued a report, which included some observations in the last 20th

century. They reported positive changes in rainfall after 1916, which became greater after

the 1950s, and reached ~30% increase from 1956 to 1991 in the region from 20 to 35 S

(CLIVAR, 1999). According to Climagro, a nongovernmental organization in Argentina

that provides seasonal forecasts and technical support to farmers, cycles have been

observed as 4 cycles of rain in the last century. The first cycle was described as a dry

period, which began approximately in the mid 1920s, and included 3 drought campaigns.

The next phase was a transitional period from dry to humid found in the 1950s. In the

1970s it is believed and reported extensively that a more humid period was taking place.

This coincides with extensive land use changes and increase in the agricultural sector in

Argentina and the Pampas as a whole (University of Miami, 2006; Viglizzo et al., 1997)

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Viglizzo et al. (1997) hypothesized that that land-use changes were driven by climate

during this time. Their study confirms the Climagro estimates and found steeper slopes in

semi-arid zones of the Pampas and a shift of increased humidity towards the west, which

is a semi-arid region. The most recent cycle began in the early 1990s and is considered a

transition period from humid to drier conditions. Less harsh summers, warmer winters,

and a delayed onset of frost have been reported in the region (Climagro, 2006). The

1990s were reported to be the warmest years on record in the 20th

century for Argentina

and agrees with global mean temperature trends (Loustau, 2002). It is also suggested that

the Pacific Decadal Oscilliation (PDO) may also affect the region. The PDO is a larger-

scale pattern that is ENSO-like that can persist 20 to 30 years as observed through the last

century. However it is most visible in the Northwest U.S. with some influence observed

in the tropics (NOAA, 2006; University of Washington, 2006). Climagro (2006) suggests

that the PDO is currently in a negative phase, which should mean drier conditions for the

Pampas region. However there is still a debate about the causes of the PDO and its

predictability, and thus, there is much skepticism that it is cause of current trends in

southern South America (CLIVAR, 1999).

V. Climate Change

Several climate changes have been documented in Argentina within the last century. The

annual mean temperature has increased by 1°C and the 1990s was the warmest decade on

record in the 20th

century agreeing with global trends. Also, the frequency of frosts has

decreased and the number of frost days per year has decreased by 10%. See Figure 2 for

changes in annual mean temperatures and annual frost frequency in Argentina for 1901 -

1998. Annual rainfall has increased by 10% and summer rainfall has increased by 10%.

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See Figure 3 for seasonal rainfall in the summer and autumn in Argentina for 1901 to

1998. In the Pampas, rainfall has increased by approximately 15% (Hulme & Sheard,

1999). In a study by Barros & Silvestri (2002), which examined long-term trends in Plata

basin scale rainfall patterns over the last fifty years, it was found that rainfall amounts

had increased at boundaries between humid and semi-arid regions in Argentina from

December to February. The authors believe this trend was due to a stronger South

Atlantic Anti-cyclone moving further westward along the continent and agrees with the

Viglizzo et al. study (1997). This would imply that farmers in these regions might have

experienced an extended rainfall period (October-November, December-February,

March-April).

Figure 6. Argentina Annual Mean Temperature & Frost Frequency in 20

th century

Changes are with respect to the average 1961 – 1990 climate values of 14.5 C and 69 days.

Figure 7. Argentina Seasonal Precipitation Anomalies for Summer and Autumn in 20

th century

Changes are with respect to the average 1961 – 1990 values of 211 mm and 168 mm.

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Source: Hulme & Sheard (1999)

According to Loustau (2002), global warming puts Argentina in a double jeopardy

because they are reliant on rain for agriculture and susceptible to climate variability. She

believes the Pampas will be highly vulnerable to extreme precipitation events and

flooding (Loustau, 2002). Future projections do show that Argentina may warm slightly

less rapidly than global expectations and that precipitation is expected to increase as well

as anomalous precipitations events, which will increase the risk for floods. However,

there are many uncertainties associated with the hydrological cycle. In a study by Hulme

& Sheard (1999), projections for the next century were made using the IPCC carbon

emissions scenarios that range from the lowest emissions with lowest climate sensitivity

(B1) to highest emissions with the highest sensitivity (A2). The B1 scenario shows that

temperatures in the Pampas warm ~.4 to .7 degrees Celsius (C) in the 2020s, ~.7 to 1.0 C

in the 2050s, and .~9 to 1.4 C in the 2080s. In the A2 scenario, the results showed that

temperatures in the Pampas region may increase ~1.0 to 1.5 C in the 2020s, ~ 1.9 to 2.7 C

in the 2050s, and ~ 2.9 to 4.4 C in the 2080s. As the emissions and time increase, the

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range of temperature increases in this scenario (Hulme & Sheard, 1999). The Pampas

region may benefit due to these climatic changes. Warmer winters and more benign

summers are expected. Agricultural production is expected to increase by 2 to 5% due to

CO2 fertilization and some crops such as soybean yields are expected to increase

(Loustau, 2002). However climate is not the only factor and crop response to global

warming requires further investigation. Also, there are some negative implications.

Increased agricultural production will lead to increases in land-use changes. Maize yields

are expected to decrease and yields in general may decrease due to loss of nutrients

incurred from increased flooding events. The farming communities are aware of these

changes and have begun discussing mitigation strategies, including the use of climate

information. There is even a campaign to minimize carbon emissions from agricultural

practices (Loustau, 2002).

VI. Conclusions

In conclusion, climate variability is the most serious concern for Argentine farmers and

communities in the Pampas. Changes in the tropical Pacific Ocean are among several

climatic influences in the region and it seems that other influences such as decadal

intervals may also play a role. Further research is needed in order to fully understand the

variability patterns in southern South America, and afford the scientists and communities

in the region a chance to mitigate future climate risks and enhance current livelihoods. If

climate change scenarios are correct for this region as projected by Hulme & Sheard, then

the Pampas may initially benefit in the short run; but as projections (worst case scenario)

also show, variability in the range of climate will increase as time increases, and thus,

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increasing the risks. However the Pampas seem to have some capacity already existing

within their community and therefore, the future risk management may be enhanced.

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