It is also the worst-case climate risk scenario currently playing out live.
According to Monday's study in Nature Climate Change, the dramatic drying of 2021 -- which was as dry as 2002 and one the driest years for the region -- has pushed the 22-year drought past megadroughts record-holder in the late 1500s. It shows no sign of abating in the near future.
According to the study, 42% of this megadrought could be attributed directly to climate change.
Park Williams, a UCLA climate hydrologist and study lead author, stated that "Climate Change is shifting the baseline conditions towards a drier. This is in line with the worst-case scenario that people considered in the 1900s. However, I believe we should be preparing for worse future conditions.
Williams examined soil moisture levels in West, which includes California, Wyoming and Utah, Nevada and Arizona. He used modern measurements and tree rings to estimate the back year 800. This is about the most reliable tree-ring-based estimate you can make.
"This drought is really severe; it's one the worst handfuls of years since the year 1800 A.D." Williams stated to CBS News. "So, now humans are facing a water shortage crisis in the West that no modern society has ever had to deal with."
Williams studied the current drought a few years back and determined that it was a long and deep megadrought and that the worst one was in the 1500s. Williams concluded that the current drought would not surpass it because megadroughts tend to end after 20 years. He said that 2019 was a dry year, so the western drought could be ending.
However, the region was dry in 2021 and 2020.
According to the U.S. drought monitor, California was in an official drought state from mid-May through the end of 2021. At least three quarters of California was at the worst two drought levels between June and Christmas.
Williams stated that the drought has "just cranked back to maximum drought severity in late 2020-2021 is an emphatic statement made by this 2000s drought, saying that we are nowhere near the end." He stated that the drought is now 5% more dry than the 1500s record.
According to the drought monitor, 55% of the U.S. West are in drought. 13% of them are experiencing the worst drought conditions.
Williams stated that the megadrought began in 2002, which was based on tree rings and humidity.
Williams stated that Williams was asking if they would ever see another year like 2002 in their lives. In fact, Williams saw it in the same drought 20 years later. Although the drought levels of 2002 and 2021 were statistically equal, they still lag behind 1580 for the worst year.
Scientists say climate change is increasing heat and evaporation due to the burning fossil fuels.
Williams created a hypothetical world using 29 models. He then compared it with what actually happened in real life. This is the scientifically accepted method to determine if extreme weather events are due to climate change. His research showed that 42% are directly due to human-caused global warming. He said that the megadrought wouldn't have occurred without climate change because 2005 and 2006 would not have been sufficiently wet to end it.
Jonathan Overpeck, University of Michigan dean of environment, said that the study was "an important wake-up call." He wasn't involved in the study. Climate change is literally baking water supplies and forests in the Southwest. It could get worse if we don’t stop it soon.
Williams stated that there is a direct correlation between drought and heat, and the increase in wildfires which have decimated the West over the years. Dry fuel is what drought and heat provide for fires.
Williams stated that this megadrought would end eventually due to the good fortune of a few rainy years. Then, another one will begin.
Daniel Swain, a UCLA climate scientist, stated that megadrought is likely to become a permanent feature in the climate of Colorado River watersheds during the 21st Century.
Snow is the most important thing for the West. The snowpack of the mountains melts in the summer and flows into the reservoirs.
According to J.T Reager (a NASA water scientist), snow in the West is like a battery. It's where we store our water." CBS News interviewed J.T Reager. "Now we are getting less snow. The snow season is significantly shorter.
The West is becoming hotter and dryer due to climate change. This means that more rain is falling than snow, and that much of it is evaporating.
Reager stated, "Over the long term, what we see with our satellite data [is] a picture of continuous drying."
NASA's satellite documents the loss of water in mountains, reservoirs and underground aquifers.
Reager stated that these images were taken by the satellite mission in April 2010, 2015, and 2021. They show the steady drying of water in West.