Outlook on climate change adaptation in the Tropical Andes mountains

clear overall than changes in temperature, as the rugged topography of the Andes influences the generalizability of precipitation measurements. Most importantly though, the internal variability (such as year-to-year differences) is very large for precipitation, and therefore any climate change signal must be very strong to be visible in this variability (and it isn’t). The trends observed are that precipitation has increased in the inner tropics but decreased in the outer tropics (Magrin et al., 2014). Bolivia and southern Peru have the biggest problems with water shortages. The north-western coast of Peru and the hyper-humid Ecuadorian Choco have experienced an increase in precipitation, while the drier Altiplano area has observed a decrease. Changing seasonality is perhaps the most important change in precipitation patterns observed so far. In the south in particular, there are indications that the rainy season has become more intense and more seasonally concentrated, while the dry season has become longer (Seth et al., 2010). Precipitation in the Tropical Andes also has great yearly and decadal variation. This is mainly due to the El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) climate systems. It is important to remember that ENSO events have spatially and temporally different and asynchronous effects in different parts of the Tropical Andes. Along the lower slopes of the Tropical Andes, El Niño events generally cause heavy rainfall. However, this rainfall does not reach above 2000 m.a.s.l. In fact, El Niño events generally lead to warm and dry weather in the high elevations of the Tropical Andes and along the eastern slopes. La Niña events, on the contrary, generally cause cold and wet conditions in the high mountains. In the Central Andes, this influence is less significant and less uniform (Chevallier et al., 2010).

The effect of El Niño on weather in the Andes

Wet conditions

Dry conditions

Raising of warmmoist air

Low soil moisture

South East trade winds reversed or weakened

Severe droughts Droughts in the Andes Intense summer rainfall

Warmwaters accumulates on South America’s coast

Dryer than usual

Warm ocean layer

Cold ocean layer

Cold and warm episodes Oceanic Niño Index

2,25

1,50

0,75

0

-0,75

-1,50

1950

1960

1970

1980

1990

2000

2010 2015

Source: National Oceanic And Atmospheric Administration

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