By: Jose Caceres
Peru, located at a tropical latitude, in the proximity of the Equatorial line and at the shores of the Pacific Ocean in the western side of South America, is often assumed to possess a tropical climate. This is in part true, but given Peru’s rough landscape and the influence of the rather cold waters of the Pacific Ocean among other factors, make of this 1.285 million sq. Km land a true catalog of climates and micro-climates.
The rough landscape that I am referring to accounts for the presence of the tallest tropical mountain range in the world -Cordillera Blanca- with peaks that soar to an altitude of 6768 meters above sea level at its highest point, in the Huascaran mountain. Cordillera Blanca is only a segment of the Andes mountain range, being the Andes some sort of a ‘dorsal spine’ for Peru, as it runs all along the country from the Northwest to the Southeast.
When it comes to the ocean current that runs along the western coast of Peru, this segment of the Pacific Ocean is identified as the Humboldt current. The Humboldt current given its colder temperatures in an otherwise tropical waters, has a considerable cooling influence on the climate of Peru (and also of Chile) and is responsible also of the aridity of the Peruvian and Northern Chilean coast, which conforms the Atacama Desert, the driest – most arid in the world.
Seasonal disruptions by the southbound Niño’s ‘warm’ current counterbalance the effects of the Humboldt ‘cold’ current, bringing down the ‘thermal inversion’ produced by the cold waters at this tropical latitude and altering the patterns of the climate, particularly when its intensity (of the Niño’s current) is deemed high. Atypically strong Niño’s current appearances not only cause havoc with Peru’s weather but also at a global context, since its effects echo in a sort of chain reaction all around the world each time that this occurs.
With all the above said, and in a ‘nutshell’, Peru has three main geographical regions (Figure 1): The Coast which is mostly arid. The Mountain region, which in accordance to the altitude goes from sub-tropical (western slope) or tropical (eastern slope) in the lowlands to cold and with presence of glaciers in the highlands, and the third major geographical region being the tropical rainforest, the Amazon, which extends east of the Andes and that accounts for more than 50% of the Peruvian territory.
Figure 1: Geographical Map of Peru
Instrumental data collected in various meteorological stations in Peru provide evidence that the average temperature is rising and that the effects of global warming are being felt in this country. A proof that this is occurring is the accelerated retreat of the tropical Andean glaciers.
The NOAA (National Oceanic and Atmospheric Administration) provides weather historic data from meteorological stations all around the world. The information collected for this study is from the NOAA data-center and corresponds to 11 stations from Peru. The stations chosen gather quantitative information since the 1950’s. These stations are distributed throughout the country and in the 3 main geographical regions as previously described: 5 in the Coastal region, 2 in the Andean region and 4 in the Eastern rain-forest.
In order to understand the Peruvian case, it is important first to recognize the global scenario and to identify the main forces that could be acting together in creating this warming. The broad picture can help also on clarifying to at which extent this is due to natural causes or due to human activity (anthropogenic).
The Global Trend:
The figure below (Fig. 2) provides a chart (lower right section) of the ‘Global Mean Temperature Estimate’, collected from stations around the world (marked as blue dots in the world map), since the year 1851 to 2011. A noticeable trend of increased temperature is observed from 1975 and onward. A 0.9 degrees C increment above the mean temperature for 1851 – 2011 is observed and a 1.1 degrees C increment above the 1950’s level.
Figure 2: Global Mean Temperature Estimate
The following figure (Fig. 3) also from stations distributed around the world (blue dots in the world map), and with data collected for the period of 1880 – 2010, shows the changes in the Solar Intensity. There is a noticeable cycle of around 11 years from peak to peak which are owed to cyclical manifestations of the Sun, such as presence of sunspots and flares. The solar intensity is a natural factor and moreover a determining one for the fluctuation of the temperature on Earth and ultimately the climate. Other factors such as Greenhouse Gases (both natural and man-made), Volcanoes, Ice Albedo, etc. act more as feedback in a way that either exacerbate (positive feedback) or stabilize (negative feedback) the global temperature trend and the climate. The cycles in the Sun intensity since the ‘valley’ in 1953 (see Figure 3) show a very regular leveled pattern which wouldn’t correlate well with the increase on the temperature for pretty much the same period of time observed in the ‘Global Mean Temperature Estimate’ figure.
Figure 3: Changes in Solar Intensity
So, before we narrow to the Peruvian case it is important to understand two things, which come as some sort of a conclusion from the previous observations at the global context:
First: The planet is warming and it has warmed already for around 1 degree since pre-industrial times. Second: Factual evidence from instrumental measurements and paleo climate methods suggest that the warming is human induced. This assumption is founded in the proven fact that carbon emissions in the form of CO2 which is a product of burning fossil fuels, has the ability to trap heat in the atmosphere and therefore to act as a positive feedback in the overall rise of the global temperature. Since this temperature rise correlates well with the man-made carbon emitted to the atmosphere during the industrial era and does not match with the solar intensity trend, it greatly points towards the assumption that the warming is not naturally induced but anthropogenic.
The Peruvian Case:
The next figure (Figure 4) shows (in the lower left side) the average temperature trend for each of the 11 stations chosen for this analysis. The results give a composite temperature trend increase of 0.25 degrees C per decade from the year 1950 to 2013. That means an increase of 0.025 degrees per year and an accumulated increase of 1.575 degrees C, almost half of a degree above the global average for quite the same time period.
Figure 4: Temperature Trend, degrees C/decade in 11 meteorological stations in Peru
The compelling evidence:
A verification of the findings provided by the meteorological data is the volume of ice in the tropical Andean glaciers, since mountain glaciers are particularly sensitive to climate change. The evidence is so palpable that not even climate change deniers could underestimate it. The Andean glaciers are shrinking, the smaller glaciers are disappearing altogether, many glaciers of the recent past no longer exist and this is occurring at an alarming rate. It is worth noting that tropical Andean glaciers have been in retreat since the last glacial maximum, also called ‘little ice age’ and that was around AD 1730-50, but the pace of ice depletion at which this is occurring now is much faster. The graphic below, also provided from the NOAA data-set provides information on the measurements of the length of the Zongo glacier in the Peruvian neighbor to the South East, Bolivia. Note the steeper decline from the year 1982 and onward.
Figure 5: Zongo glacier length
The glaciologist and mountaineer Bernard Francou in an article written in January 2015 for The Guardian, in reference to the tropical Andean glaciers of South American, of from which 70% of them belong to Peru, stated: “Glacier depletion has increased dramatically in the second half of the 20th century, especially after 1976. We can claim that in recent decades the glacier recession moved at a rate unprecedented for at least the last three centuries – in 30 years, they have lost between 35% and 50% of their area and volume”.
Figure 6: The changing face of Andean glaciers
Left: Pucaranracocha glacier, in the Cordillera Blanca, in 1932. Credit: Erwin Schneider, courtesy of the Association for Comparative Alpine Research, Munich. Right: Pucaranracocha glacier, in the Cordillera Blanca, in 2009. The glacier has retreated hundreds of meters already. Credit: Alton C. Byers, The Mountain Institute
The tangible effects of Global Warming – Conclusions:
The climate is warming at the world context and the Peruvian case is only a confirmation of it. Among the multiple impacts of this climate change, the retreat of the tropical Andean glaciers represent a vivid example.
In the context of Peru (this assertion can be extrapolated to the whole region), the reduction of the glaciers directly affects the water resources and the ecosystems linked to them, and consequently to the communities that depend on these resources. Note that the river currents and water reservoirs, both necessary for agriculture and hydro-power, depend on a steady flow of water provided a regular and cyclical pattern of glacier ice melting.
At a broader scope the effect of the retreat of the glaciers in Peru has repercussions for the whole country. The ‘ripple’ effect of it initiates on the agricultural sector and then derives in migration from the rural areas to the cities and thus adding strain in the urban services and infrastructure. Power generation is also affected as the hydroelectric production is intrinsically connected to the water reservoirs.
The information provided in this article is factual and the Peruvian case as reviewed in this report is nothing but the testament of a global reality.
Information source: The technical data compiled for this report is from NOAA (National Oceanic and Atmospheric Administration) and can be found in: http://climatemodels.uchicago.edu/timeseries/#DgpBDBIBCDIDB
