“Hail, more rain, greater heat and cold, a greater quantity of crop pests”.
“The peaches are flowering now, instead of in August. [It used to be] that winter lasted until September. Now you don’t know…Where there isn’t supposed to be rain, there’s rain.”
“New crop pests…including pests we’ve never seen before in Cuzco.”
“Higher temperatures…new diseases in crops and animals.”
Over and over again during my stay in Cuzco, I’ve heard the same things. Temperatures are more extreme now than they used to be. Seasons have shifted. New insects and pests have appeared.
The obvious conclusion is that all of these changes are due to global warming. Of course, it’s never quite that simple. Localized environmental problems--like overgrazing and deforestation—also affect temperature and precipitation patterns. What’s more, El Nino often determines yearly weather patterns in Peru, meaning that a high degree of variability is an inherent feature of Peru’s climate.
In order to determine which changes are truly attributable to global warming, we have to turn to climate science. In order to predict climate change impacts in specific countries, climate scientists make use of regional climate models. These operate on the same principles as global models, but on an entirely different scale. (Instead of dividing the entire world into boxes 200 kilometers square, a regional model might split an area the size of Peru into sections 20 kilometers across.) As a result, these models can deliver predictions tailored to a particular watershed or even a particular town.
They take as their inputs the results from global models. For instance, let’s say that the HadCM3 global climate model has suggested that under the A1B emissions scenario, sea temperatures will rise by 2 degrees and air temperatures by four degrees by 2050. A regional model for Peru can then tell us what those changes will mean for rainfall in Cuzco or heat-waves in Lima. Of course, this approach has its weaknesses. Regional models are highly dependent on getting correct inputs from the global models, and they are expensive and cumbersome to create. It can be difficult to compare results from different regional models, as they may be based on different global models, use different time-frames, or consider different emissions scenarios.
Still, regional models can offer some suggestion of what lies ahead. Take the Urumbamba watershed, which encompasses much of Cuzco. According to one model for this area, maximum summer temperatures will rise by as much as 3 degrees C between now and 2100. Rainy season precipitation will increase by 10 to 24%, while dry season precipitation will fall by 50% in high-altitude areas (above 9000 feet). In Piura, which is one of the places I’m headed next, maximum temperatures will rise by as much as 2 degrees in the next fifteen years. Precipitation will probably increase overall, with some decreases in dry season precipitation. (The source for this information is Peru`s Second National Communication to the UNFCCC).
Because these predictions can be quite uncertain, especially when it comes to changes in rainfall and precipitation, it may make sense to prepare communities for more variable weather overall, instead of preparing for specific changes or impacts. This is especially true here, given the possibility that global warming will strengthen El Nino and thus increase Peru´s overall climate variability.
One thing that seems to be without doubt is that global warming will trigger glacial melt (although how much, and how fast, is still up for debate). According to a 2009 World Bank report, Peru has already lost 22% of its glacial ice. At this pace, Andean glaciers could disappear entirely within the next few decades.
This is problematic for several reasons. Glacial melt can trigger massive floods; meltwater is often held back by ice dams, which can burst suddenly, drowning downstream homes and communities. Glaciers also perform a crucial water storage role by building up ice during wet months and releasing it as meltwater over the course of the dry season. With glaciers shrinking or disappearing, water shortages will become more acute, especially on Peru’s dry coast.
According to Peru`s Central Reserve Bank, crop losses, floods, and water shortages mean that climate change could ultimately cost the country as much as $900 billion over the next forty years. (For comparison, Peru´s GDP in 2010 was about $170 billion). That`s no small potatoes! (Ha, ha, ha).