Peru Latest Example of Climate Fueled Extremes
March 27, 2017
The world’s costliest flood disaster of 2017 is still unfolding across parts of coastal Peru, where extreme rainfall atop normally dry terrain has led to episodes of major flooding over the last few weeks. More than 110,000 people have been displaced by flooding since December, according to Reuters, and more than 80 deaths have been reported.
The death toll makes the floods of 2017 Peru’s deadliest floods since 2009 – 2010, when 158 people died in flooding between December and March. Preliminary damages from the 2017 rains and flooding in Peru are estimated at $1.4 billion (0.7% of Peru’s GDP), according to insurance broker Aon Benfield. Significant damage has been done to Peru’s infrastructure, with 2,188 kilometers (1,360 miles) of main roads and 928 kilometers (577 miles) of rural roads destroyed, along with 194 bridges. Approximately 671 kilometers (417 miles) of irrigation canals have been destroyed and as many as 23,000 hectares (56,000 acres) of crops damaged or destroyed, including grapes, mangoes, and bananas.
In the video above, scientists connect extreme events to first order physics, i.e., warmer air holds more moisture.
Recent research dives deeper, making stronger connections between climate caused changes in the jet stream, and more extreme events.
Unprecedented summer warmth and flooding, forest fires, drought and torrential rain—extreme weather events are occurring more and more often, but now an international team of climate scientists has found a connection between many extreme weather events and the impact climate change is having on the jet stream.
“We came as close as one can to demonstrating a direct link between climate change and a large family of extreme recent weather events,” said Michael Mann, distinguished professor of atmospheric science and director, Earth System Science Center, Penn State. “Short of actually identifying the events in the climate models.”
The unusual weather events that piqued the researchers’ interest are things such as the 2003 European heat wave, the 2010 Pakistan flood and Russian heatwave, the 2011 Texas and Oklahoma heat wave and drought and the 2015 California wildfires.
The researchers looked at a combination of roughly 50 climate models from around the world that are part of the Coupled Model Intercomparison Project Phase 5 (CMIP5), which is part of the World Climate Research Programme. These models are run using specific scenarios and producing simulated data that can be evaluated across the different models. However, while the models are useful for examining large-scale climate patterns and how they are likely to evolve over time, they cannot be relied on for an accurate depiction of extreme weather events. That is where actual observations prove critical.
The researchers looked at the historical atmospheric observations to document the conditions under which extreme weather patterns form and persist. These conditions occur when the jet stream, a global atmospheric wave of air that encompasses the Earth, becomes stationary and the peaks and troughs remain locked in place.
“Most stationary jet stream disturbances, however, will dissipate over time,” said Mann. “Under certain circumstances the wave disturbance is effectively constrained by an atmospheric wave guide, something similar to the way a coaxial cable guides a television signal. Disturbances then cannot easily dissipate, and very large amplitude swings in the jet stream north and south can remain in place as it rounds the globe.”
Scientists have been kicking these ideas around for years. More evidence now.
The new work analysed a type of extreme weather event known to be caused by changes in “planetary waves” – such as California’s ongoing record drought, and recent heatwaves in the US and Russia, as well as severe floods in Pakistan in 2010.
Planetary waves are a pattern of winds, of which the jet stream is a part, that encircle the northern hemisphere in lines that undulate from the tropics to the poles. Normally, the whole wave moves eastwards but, under certain temperature conditions, the wave can halt its movement. This leaves whole regions under the same weather for extended periods, which can turn hot spells into heatwaves and wet weather into floods.
This type of extreme weather event is known to have increased in recent decades. But the new research used observations and climate models to show that the chances of the conditions needed to halt the planetary waves occurring are significantly more likely as a result of global warming.
“Human activity has been suspected of contributing to this pattern before, but now we uncover a clear fingerprint of human activity,” said Prof Michael Mann, at Pennsylvania State University in the US and who led the study published in the journal Scientific Reports.
Kai Kornhuber, at the Potsdam Institute for Climate Impact Research (PIK) in Germany and another member of the research team, said: “We looked into dozens of different climate models, as well as into observational data, and it turns out that the temperature distribution favouring planetary wave stalling increased in almost 70% of the simulations.”
Large scale wind patterns are largely driven by the temperature difference between the poles and the tropics. But global warming is altering this difference because the Arctic is heating up faster than lower latitudes and because land areas are heating up faster than the oceans.