Climate Sense

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Adapting to climate change and variability

Jorge F. Carrasco, Dirección Meteorológica de Chile, Dirección General de Aeronáutica Civil

he Chilean continental territory is located on the western

side of South America between 17°30’ and 56°30’ S. It has

a total surface area of 756,096 kilometres squared, which

spans 4,300 kilometres from north to south and is limited to the

west by the Southern Pacific Ocean and to the east by the Andes

mountains. With this geographical location, Chile is character-

ized by a large variety of climates: being home to one of the driest

places in the world (the Atacama Desert) as well as the cold and

snowy Patagonian ice fields. From an atmospheric viewpoint,

the climate is determined by the presence of the permanent

Southern Pacific high-pressure centre, the westerly circula-

tion and the summer monsoon type circulation in the southern

Amazon basin. The annual cycles in temperature and precipita-

tion, as well as other meteorological variables, are related to the

seasonal variation of these features and their interannual vari-

ability is mainly associated with El Niño Southern Oscillation

and the Antarctic Annular Mode. Interdecadal changes can be

related to the Pacific Decadal Oscillation (PDO) and secular

long-term tendencies can be attributed to the greenhouse effect.

The IPCC Fourth Assessment Report indicates an overall warming,

ranging from0.2 to 1.1ºC in the northern, central and southernmost parts

of Chile, while it revealed a cooling of -0.2 to -0.5ºC in the region between

38 and 43ºS during the 1901-2005 period. However, an

overall cooling of -0.2ºC per decade has occurred in the

northern and central coast of Chile (17º-37ºS) along with

a warming of +0.25°C per decade in the inland and Andes

sectors during the period 1979-2006. This coastal behaviour

is associated with the PDO, which showed a phase change

during 1976-77.

The secular precipitation behaviour during the 1950-

2006 period shows no statistically significant tendency

for the central (30-38ºS) and southernmost parts of Chile

(south of 52ºS), while a decrease in precipitation does

occur in the southern part between 38° to 46ºS, which is

statistically significant in some locations. Although the

scarce precipitation records in the northern Altiplano allow

only a limited examination of the precipitation trends, the

long-trend behaviour at Visviri, which can be considered

a reference station in the region, reveals a slight overall

increase (not statistically significant) of between 10 and 14

millimetres per decade during the full 1962-2003 period,

although a non-significant negative trend is observed since

the mid-1980s.

In terms of interannual climate variability, El Niño

Southern Oscillation is the main natural mechanism that

strongly influences the precipitation regime in the north-

ern Altiplano and the central parts of the country. Most

wet years in central Chile are related to El Niño, and dry

years with La Niña, while in the Altiplano the wet summers

are mostly associated with La Niña and dry summers with

El Niño. Seasonal sea surface temperature forecasts have

significantly improved during recent decades, allowing for

predictions of the development and future stages of El Niño

Southern Oscillation. This has made possible the develop-

ment and implementation of the statistical seasonal forecast

(three months in advance) for precipitation and tempera-

ture in the Chilean National Weather Service. The climate

variability and the climate seasonal prediction are priority

issues because of the immediate impact that precipitation

has on many sectors. For this reason, these forecasts are

issued every month and are publicly available on the insti-

tutional webpage. They are also sent to the Secretary of

Agriculture, National Emergency Office, Water Resources

Office and Secretary of Energy–among other organizations

– for specified purposes.

The Intergovernmental Panel onClimate Change (IPCC)

global climate model projections for different scenarios for

the end the 21st century show an overall warming of at least

+2 to +4°C with respect to present conditions (1961-1990

period). This prediction is for the entire country, with the

overnance

and

olicy

Future decrease in precipitation in central and southern Chile will have a strong

impact on water resources (Rapel Dam)

Image: Janette Calderon