BBC’s Californian Megadrought Fairy Tale

By Paul Homewood

 

This garbage is laughingly presented as a factual piece!

 

 

 image

In our monthly feature, Then and Now, we reveal some of the ways that planet Earth has been changing against the backdrop of a warming world. Here, we look at the effects of extreme weather on a crucial reservoir that supplies water to millions of people in northern California.

This year is likely to be critically dry for California. Winter storms that dumped heavy snow and rain across the state are not expected to be substantial enough to counterbalance drought conditions.

Lake Oroville plays a key role in California’s complex water delivery system.

This 65km-square body of water north of Sacramento is the second-largest reservoir in California.

Not only does Lake Oroville store water, it helps control flooding elsewhere in the region, assists with the maintenance of water quality and boosts the health of fisheries downstream.

In 2014, more than 80% of California was in the grip of an "extreme drought". Against this backdrop, Oroville’s capacity fell to 30% – a historic low level.

As the water level receded to hundreds of feet below normal levels, ramps and roads no longer reached the water’s edge.

More worryingly, the reservoir – when full – provided enough water for an estimated seven million households, as well as providing power for hydroelectricity facilities and irrigation for agricultural land.

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‘Unusually destructive’

The dry conditions didn’t start in 2014, however, there had been a drought for years prior to Oroville recording its historic low level.

Indeed, the US space agency’s Earth Observatory had warned that the multi-year drought was having a wider impact on the region. Among its effects was a contribution to "unusually active and destructive" fire seasons and poor yields from agricultural land.

"There is strong evidence from climate models and centuries of tree ring data that suggest about one-third to one-half of the severity of the current drought can be attributed to climate change," observed Benjamin Cook, a climate scientist from Nasa’s Goddard Institute for Space Studies in New York.

Agency scientists added that the data suggested a "megadrought" might already be underway in this region – and that it could last for decades.

The latest update from the US Drought Monitor in December 2020, showed that much of the country’s western states were gripped by extreme or exceptional drought, with Nevada, Utah, Arizona and New Mexico, Colorado and western Texas being the worst affected.

The damaged spillway and the eroded hillside at the Oroville Dam

The emergency spillway at the dam was predicted to collapse

 

From one extreme…

Climate change is not just about a warmer world, it also means that the planet will see more extreme environmental conditions and weather. So, for example, episodes of flooding will increase, as well as episodes of droughts.

Lake Oroville was a perfect illustration of how these extremes can threaten our existing infrastructure.

While the lake’s levels reached a historic low in 2014, the reservoir’s vast embankment dam – the tallest in the US – was pushed to breaking point in February 2017.

Following fierce storms in the surrounding mountains, water was flowing into the lake at a rate of roughly one-and-a-half Olympic-size swimming pools each second.

In the space of two years, the lake went from an unprecedented low to a capacity that had not been experienced before. Water cascaded over the emergency spillways, which had not previously been required.

https://www.bbc.co.uk/news/science-environment-56225862

 

When we look at the actual data however, we find that the 2014 drought was not unprecedented – worse droughts had occurred in 1923/4 and 1976/7. Nor were the years leading up to 2014 particularly dry. Megadrought it most certainly was not!

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Climate at a Glance | National Centers for Environmental Information (NCEI) (noaa.gov)

It is also apparent that California’s climate annual rainfall has always swung  from one extreme to another. Plainly the heavy rainfall which led to the overspill at Oroville was not unprecedented either.

Nor is there any evidence that this year will be “critically dry”, with winter rainfall only the 19th lowest on record. Clearly there is no trend either towards drier winters.

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Taking a longer perspective, the chart from NOAA below shows that droughts have regularly been much worse in the past:

 CA_pdsi_V2

https://statesummaries.ncics.org/chapter/ca/ 

 

As I started by saying, this is presented as a factual piece. Let us examine two specific statements:

1) Agency scientists added that the data suggested a "megadrought" might already be underway in this region – and that it could last for decades.

As we have seen, since 2014 rainfall has returned to typical levels for California.

 

 2) Climate change is not just about a warmer world, it also means that the planet will see more extreme environmental conditions and weather. So, for example, episodes of flooding will increase, as well as episodes of droughts.

Regardless of climate models may say about the future, the weather in California is no more extreme than it has always been.

via NOT A LOT OF PEOPLE KNOW THAT

https://ift.tt/3torj98

March 15, 2021 at 06:18AM

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