Guest post by Jim Steele
published in the Pacifica Tribune February 25, 2020
Low-tech weathervanes have provided farmers with sage weather advice. If winds were coming from the north, temperatures would be colder than normal; if from the south, temperatures would be warmer. Most fascinating, if winds descended down a mountain slope, they could expect fluctuating extreme weather, with temperatures bouncing between extreme warmth and cold. Across the globe, local downslope winds cause dramatic weather changes and so are given special names such as Chinooks or Foehn winds.
In the western USA, warm dry winter winds descending from the Rocky Mountains are called Chinooks. Because chinooks can melt a foot of snow in one day, Native American Blackfeet people called chinooks “snow-eaters”. Long before it became fashionable to blame warm events on CO2 global warming, standard physics explained extreme warming events. When moist winds are forced over a mountain range, the water vapor condenses at higher elevations releasing precipitation as well as latent heat that warms the air. Then as the winds descend, the air further warms by 5.5°F for every 1000-foot drop in elevation.
For a historical perspective, read the peer-reviewed account of the “Battle of the Chinook Wind at Havre, Montana”. In December 1933 the onset of Chinook winds raised temperatures 27°F in just 5 minutes, and over the next 36 hours temperatures rose by 53°F. When the Chinooks relaxed, typical cold winter air returned, and temperatures fell 40°F in just 2 hours. Montana is a local hot spot for extreme Chinooks. The world record for the greatest warming in 24 hours happened January 1972, just 60 miles away from Havre, as temperatures jumped 103°F (−54 °F to 49 °F).
Such dramatic warming in winter seems unbelievable, but the laws of physics steadfastly state increasing pressure increases temperature without adding heat. As air moves down slope and compresses, it warms. Amazingly, tribes from Borneo to the Philippines beneficially applied the physics of warming long ago. They started fires by rapidly compressing air in a tube. Many modern backpackers carry a similar device called a “fire piston”.
When downslope winds warm and dry the air, they also drive major wildfires. In southern California these periodic wind events are called the Santa Anas, or the Diablo winds in northern California. These rapidly warming wind events dry out grasses and twigs in just a few hours making them easily ignited even in winter. Simultaneously those winds fan the flames, rapidly spreading the fire. A 1960s government report warned those winds made California vulnerable to fire all year long.
In the Swiss Alps, these downslope winds are called foehn winds. And similarly, due to foehn winds fire season in some Swiss valleys peak in the cooler months of March and April. In southeastern Australia where bushfires recently devastated the land, large fires are more likely downslope of the local “Australian Alps” due to foehn-like winds. When human ignitions and poorly managed forests coincide with foehn events, deadly conflagrations ensue.
Antarctica doesn’t experience wildfires, but foehn winds bring extreme temperatures and melt ice. Unlike most of Antarctica, the Esperanza weather station is uniquely situated between cold winds blowing from the continent that battle warm subtropical winds from the north. It is also located in a regional hot spot for foehn winds. On February 6, 2020, a foehn wind raised Esperanza’s normal 32°F summer temperatures to 64.9°F in just 6 hours. A record for the continent but much below nearby Signy Island’s 1982 record of 67.6°F, also driven by foehn winds. Twelve hours after the foehn wind relaxed, the cold winds returned dropping Esperanza’s temperatures back to its normal 32°F. Similar foehn wind events are implicated in the collapse of that region’s Larsen B ice shelf.
Climate change requires 30+ years to detect, but the sharp spike in Antarctic warming came and went over a period of hours. But talking heads mistakenly blamed the warm event on climate change, despite the region’s 2 decade long cooling trend. MSNBC interviewed New York Times reporter Kendra Pierre-Louis, who claimed Esperanza’s extreme temperature verified that climate “models are right” so we must “rein in our greenhouse gas emissions”. But nobody ever mentioned the warming was a natural foehn event. Nor did they mention that the only way to prevent such dramatic warming from foehn events, would require leveling all the mountains of the world. Looking more ill-informed, when Kendra stated this event was “not great for the animals that live in Antarctica”, MSNBC flashed a photo of polar bears.
Instead of informing the public about the science behind these amazing wind effects, they’ve hijacked natural warm weather events to create sensational and misleading climate crisis stories. The public should demand more rigorous scientific reporting!
Jim Steele is Director emeritus of San Francisco State’s Sierra Nevada Field Campus and authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism