The past month has been marked by dozens of fires, floods, droughts, heat waves and other catastrophic weather events, which have been intensified by human-induced climate change. Atmospheric scientists have relied on data from satellites to help them issue forecasts and warnings, while keeping abreast of the long-term temperament of the atmosphere.
Here we take a look at some of the most striking images shared by weather satellites in recent weeks.
Falling water levels in Lake Meade
Lake Meade, located in southern Nevada and northern Arizona, is the largest reservoir in the United States, formed after the construction of the Hoover Dam in the late 1920s and 1930s. Some 20 million Americans depend on its water, especially in the Los Angeles metropolitan area.
Since 1983, a combination of increased water demand and persistent drought has kept the reservoir below capacity; today it is at record highs. NASA writes that at full capacity, water levels would be 1,220 feet where the man-made lake meets the Hoover Dam. Instead, that level currently sits at 1,040.65 feet. Last year at this time it was 1,068 feet, and a year before it was 1,085 feet.
“About 10% of Lake Mead’s water comes annually from local precipitation and groundwater,” NASA wrote, “with the rest coming from snowmelt in the Rocky Mountains that flows along the river’s watershed. Colorado through Lake Powell, Glen Canyon and the Grand Canyon.”
This means that Lake Meade is not just a barometer of how much rain has fallen. It is an indicator of the larger water supply of the West as a whole, much of which is stored in the winter snowpack. North of Lake Meade, Lake Powell is only 27% capacity according to NASA, and the entire Colorado River system is at 35%.
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More than a third of the western United States is listed as being in “extreme” or “exceptional” drought – the two most severe levels on the US Drought Monitor scale – with southern Nevada solidly in exceptional shade.
“Tank levels are critically low,” wrote the Drought Monitor. “Hydroelectricity production is limited, alternative energy is expensive; groundwater is decreasing; water allocations to farmers and herders are reduced. It also notes that “the viability of ecosystems is threatened”.
Many climate change experts expect the drought in the West to only get worse in the years to come.
Explosive wildfires in California
The drought has fostered conditions conducive to explosive wildfire development and extreme fire behavior, both of which have manifested in recent weeks across the Golden State. California fires are burning precariously near Yosemite National Park, including the Oak Fire, which erupted on Friday.
So far, the Oak Fire has burned 18,532 acres in Mariposa County near Highway 140 and Carstens Road. It is contained at 26%.
“While good progress continues on the fire, much work remains to be done,” wrote Cal Fire, the agency tasked with overseeing firefighting.
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Tom Yulsman, director of the Center for Environmental Journalism at the University of Colorado and contributor to Discover Magazine, used Landsat satellite imagery to produce the three-dimensional flyby above.
Eighteen of the 20 largest wildfires in California state history have occurred since 2003. Human-caused climate change is amplifying drought and excessive heat that promote more extreme wildfires.
Fires in Portugal, Spain and France
More than 1,000 people have died amid a record-breaking heatwave that brought searing temperatures to western Europe one to two weeks ago and triggered the UK’s first-ever ‘red warning’ for heat . Temperatures hit 40 degrees Celsius (104 Fahrenheit) for the first time on record there, with nearly three dozen weather stations beating the UK’s previous record of 38.7 Celsius (101.7 Fahrenheit).
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Forty thousand residents of France were evacuated due to forest fires, and a number of other fires torched the landscape in Portugal and Spain. Climate change has helped push the already toasty air mass into record territory, which has evaporated moisture from the ground more efficiently, drying out the landscape.
“In Portugal, temperatures reached 45 degrees Celsius (113 degrees Fahrenheit) on July 13 in the city of Leiria, where more than 3,000 hectares (7,400 acres) had burned,” NASA wrote. “More than half the country was on red alert as firefighters battled 14 active blazes.”
The day/night band from the Suomi NPP/VIIRS satellite captured the signatures of wildfires burning on the night of July 12. Visible to the west of Madrid is a fire that has burned 3,700 acres.
Extreme flooding in Saint-Louis
The effects of human-caused climate change can exacerbate extreme floods and droughts. The reason is simple: a warmer atmosphere accelerates the evaporation of water. Where storm fronts are present, such as in the US Midwest right now, the extra water in the atmosphere means heavier downpours. But in much of the western United States, where there are no such fronts, the warmed atmosphere extracts what little moisture is more efficiently from vegetation and soil, reinforcing the drought.
On Monday, residents of St. Louis woke up to a flash flood, with a number of water rescues carried out as hours of torrential downpours inundated the city. A staggering 7.78 inches of rain fell in six hours, most of which fell before sunrise. The recorded day a total of 9.04 inches at St. Louis International Airport — about a quarter of the city’s average annual precipitation. The historic flood, which has just a 0.1% chance of occurring in any given year, was the most extreme on record for the city. St. Peters, Mo., northwest of St. Louis, was nearly 13 inches at 4 p.m.
The origin of the flood was a stationary front draped across the metropolitan area, which served as a railroad for heavy storm cells. Record humidity was also in place.
Heavy showers are more and more frequent in Saint-Louis. Since World War II, days with 1.5 inches of rain have become about 30-40% more frequent; there has also been a slight increase in average annual precipitation in St. Louis, with data suggesting a jump from about 34 inches in the 1940s to 43 inches today.