The Andean Glacier and Water Atlas

Temperature Numerous studies have reported significant warming and a resulting glacier melting over the last decades. There is also growing evidence of altitude amplification, meaning that the rate of warming increases with elevation, resulting in high mountain regions experiencing faster than average temperature changes (Pepin et al., 2015; Urrutia and Vuille, 2009). The mean annual temperature in the countries of the northern Andes (Venezuela, Colombia, Ecuador, and Peru) has increased by ~0.8°C during the 20th century (Marengo et al., 2011). Surface temperatures in the high-altitude areas of the Tropical Andes have increased of ~0.1°C per decade over the last 50 years (Vuille et al., 2015). This warming has resulted in the altitude of the freezing level height (zero-degree isotherm) rising by an average of ~45 m across the region (Bradley et al., 2009). Temperature predictions for the Andes using the high emission climate change scenarios (Jiang et al. 2000; IPCC, 2014) indicate that temperatures in the Andes could increase by 2–5 °C by the end of the 21st century (Hijmans et al., 2005; Cabré et al., 2016). The degree of warming varies, but according to one study, it could be most intense at high elevations in the Cordillera Blanca region in Peru (Urrutia and Vuille, 2009). In addition, by 2100 there could be a much larger inter-annual temperature variability, a higher likelihood of extremely hot years, with even the coldest years much warmer than the warmest years observed today (Urrutia and Vuille, 2009).

Elevation dependent warming in the Tropical Andes

Western slope

Eastern slope

Elevation

5 000m

4 500m

4 000m

3 500m

3 000m

2 500m

2 000m

1 500m

1 000m

500m

0.5

1.0

1.5

2.0

2.5

3.0 3.5 4.0 4.5 5.0

5.0

4.5

4.0

3.5

3.0

2.5 2.0 1.5 1.0 0.5 0.0

Temperature increase* with altitude range ºC

1961–1990 baseline scenario for the Andes

Source:Urrutia,R.,Vuille,M.,Climatechangeprojections for the tropicalAndesusinga regional climatemodel:Temperatureandprecipitation simulations for theendof the21stcentury,2009

GEO-GRAPHICS / GRID-Arendal 2018

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