Guest essay by Eric Worrall
A JPL led study has suggested construction of water reservoirs in the 1970s held back so much water from running into the sea it paused sea level rise.
Climate change: Dams played key role in limiting sea level rise
By Matt McGrathEnvironment correspondent
The construction of large-scale dams has played a surprising role in limiting rising seas, say scientists.
Over the past century, melting glaciers and the thermal expansion of sea water have driven up ocean levels.
But this new study finds that dams almost stalled the rising seas in the 1970s because of the amount of water they prevented from entering the oceans.
Without them, the annual rate of rise would have been around 12% higher.
…
Read more: https://www.bbc.com/news/science-environment-53836018
The abstract of the study;
The causes of sea-level rise since 1900
Thomas Frederikse, Felix Landerer, Lambert Caron, Surendra Adhikari, David Parkes, Vincent W. Humphrey, Sönke Dangendorf, Peter Hogarth, Laure Zanna, Lijing Cheng & Yun-Hao Wu
The rate of global-mean sea-level rise since 1900 has varied over time, but the contributing factors are still poorly understood1. Previous assessments found that the summed contributions of ice-mass loss, terrestrial water storage and thermal expansion of the ocean could not be reconciled with observed changes in global-mean sea level, implying that changes in sea level or some contributions to those changes were poorly constrained2,3. Recent improvements to observational data, our understanding of the main contributing processes to sea-level change and methods for estimating the individual contributions, mean another attempt at reconciliation is warranted. Here we present a probabilistic framework to reconstruct sea level since 1900 using independent observations and their inherent uncertainties. The sum of the contributions to sea-level change from thermal expansion of the ocean, ice-mass loss and changes in terrestrial water storage is consistent with the trends and multidecadal variability in observed sea level on both global and basin scales, which we reconstruct from tide-gauge records. Ice-mass loss—predominantly from glaciers—has caused twice as much sea-level rise since 1900 as has thermal expansion. Mass loss from glaciers and the Greenland Ice Sheet explains the high rates of global sea-level rise during the 1940s, while a sharp increase in water impoundment by artificial reservoirs is the main cause of the lower-than-average rates during the 1970s. The acceleration in sea-level rise since the 1970s is caused by the combination of thermal expansion of the ocean and increased ice-mass loss from Greenland. Our results reconcile the magnitude of observed global-mean sea-level rise since 1900 with estimates based on the underlying processes, implying that no additional processes are required to explain the observed changes in sea level since 1900.
Read more: https://www.nature.com/articles/s41586-020-2591-3
A few mm / year of sea level rise is no threat to anybody’s wellbeing. But I find it fascinating that constructing a few dam projects was apparently enough to stall this allegedly serious climate threat.
If building a few dams in the 1970s was enough to stall sea level rise, there are plenty of other gigantic water projects on the drawing board which would likely stall sea level rise for a few more decades, such as the Egyptian Qattara Depression Project, the CSIRO Three Rivers Northern Catchment Scheme, or one of the many variations of the Bradfield Scheme. China has a large area of useless wasteland which could conceivably be filled with water. Even filling these natural depressions with sea water in many cases could improve the local microclimate.
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making use of land below sea level that one day will eventurally be breached through land movement or pressure ??? sounds a good idea, but not to just flood it, a controlled plan would be needed to get the best for our planet and mankind. their could be some great benifits from this and will no doubt be some that are not so good but the science should be able to work these out ,,,, if people can one day work together,, could be used to produce almost free electric after costs, and that could be used to make hydro fuel on a large scale, taking the need from the oil,gas and coal ind to an extent, then their’s the climate and evaporation and it’s effect on the planet’s weather system,,,, and so much more
It’s definitely doable to drop sea level a little with fairly small environmental impact using a variety of engineering methods. The problem is that the greens don’t want any environmental impact whatsoever.
The dams don’t hold the water forever. That’s the point of dams. Less what’s lost to the atmosphere via evaporation (which probably ends up in the sea eventually), once full they release water (for power production, preventing over-flow, and/or refreshing the downstream river) which reaches the sea as it would if free-flowing. My hunch is they don’t have their mass flows computed properly. Or maybe I’m missing something.
Once full, dams make no difference to sea levels. But while filling, they are intercepting water that would have gone into the seas.
That’s exactly what I was going to post. The initial fill might delay water reaching the ocean but that would reduce sea level rise. From that point forward, water behind the dam is either released and is basically the same amount as with no dam or it is used and some reaches the sea while the rest goes into an aquifer.
Where do these people come from? I swear these people have all grown up in a city and have never experienced real physical things in the out of doors. Their only knowledge comes from computer games. Meat is grown in the backroom of the meat counter. Vegetables and fruit appear each night in the grocery storeroom by magic.
Jim
And chocolate milk comes from brown cows.
These are mostly millennial authors, without wishing to denigrate their qualifications. They have been trained to the agenda, starting with a conclusion and searching for things to validate that conclusion.
One author, David Parkes, was a co-author of this paper in 2018:
https://www.nature.com/articles/s41586-018-0687-9
“Global-mean sea-level rise (GMSLR) during the twentieth century was primarily caused by glacier and ice-sheet mass loss, thermal expansion of ocean water and changes in terrestrial water storage. Whether based on observations or results of climate models, however, the sum of estimates of each of these contributions tends to fall short of the observed GMSLR. Current estimates of the glacier contribution to GMSLR rely on the analysis of glacier inventory data, which are known to undersample the smallest glacier size classes. Here we show that from 1901 to 2015, missing and disappeared glaciers produced a sea-level equivalent (SLE) of approximately 16.7 to 48.0 millimetres.” (precisely…)
Idiotic conclusion
What a joke. Sea level rise has not changed for at least 150 years and dams slowed it down. Where’s the water?
my two cents on this issue
https://tambonthongchai.com/2020/08/20/dams-and-sea-level-rise/
So, the amount of water on the planet remains the same yet the level increases.
A better bet would be the Aral Sea which used to be the fourth largest lake in the world at around 23,000 square miles but lost around 90% of its area due to water being diverted from incoming rivers for irrigation projects, mainly cotton.
The government of Kazakhstan is now trying to restore the lake.
I think doing this is good, and refilling aquifers that have been used for agriculture. On problem though is that the greenies don’t like diverting some flow from rivers to do this. I don’t understand as so much fresh water wasted flowing to ocean from rivers.
1970s Dam Construction Paused Global Warming Sea Level Rise
If building a few dams in the 1970s was enough to stall sea level rise…
Then we need a mass building programme of swimming pools.
While I don’t doubt that the new dams had an impact on global sea level rise, I suspect the cool temperatures of the 70’s had a much bigger impact.
It’s probably also causing the melting of glaciers and increase in global temperature. All that extra water surface changes the effective land use of an area.
Presumably, all of these dams are above sea level.
They have taken a lot of water from sea level and placed it above sea level.
Has anyone calculated how many micro-seconds this has slowed the earth’s rotation by?
NASA has calculated that the Three Gorges dam slows the Earth’s rotation by a mind boggling 0.06 microseconds, which is six hundredths of a millionth of a second. So all of the dams on the planet would maybe cause a slowing of a few microseconds. Don’t rush to change your clocks as it hardly even affects the leap seconds we need to adjust to keep things in ‘time’ with natural processes.
I was reading an article yesterday about the flooding currently going on around the Three Gorges dam and the article said China hadn’t seen this much rain since the 1940’s.
Next thing you know, the Alarmists will start claiming China is experiencing unprecedented flooding and Human-caused Climate change is the reason why, but we will just have to refer them to the 1940’s. Nothing to see here.
If the world population increased by 4.2 billion people from 1970 to 2020, and the average person is 60% water, I wonder how many new dams worth of water are walking around on the planet today?
Maybe the UN can mandate making more babies to slow the sea level rise. For the common good, of course.
Somebody contact Al Gore and Greta. They need to get busy.
Did the paper compensate for pumping out ground water ?
“The rate of global-mean sea-level rise since 1900 has varied over time, but the contributing factors are still poorly understood”
Heresy! Everyone knows the science is settled and we’re all doomed to drown. I trust these deniers and spreaders of fake news have been kicked off Facebook and Twitter.
Has anyone done a more comprehensive study of the global climate/weather impacts of all these man-made reservoirs? I recall Roger Pielke Sr. co-authored a 2011 study which found evidence of micro climate changes near some large reservoirs.
So we need to build bigger toilets to hold more water and prevent sea level rise?
https://www.theguardian.com/environment/2020/aug/20/greenland-ice-sheet-lost-a-record-1m-tonnes-of-ice-per-minute-in-2019
Greenland ice sheet lost a record 1m tonnes of ice per minute in 2019
Climate-driven loss is likely to be the worst for centuries, and is pushing up sea levels
Tony Heller exposes the Guardian’s lies:
https://realclimatescience.com/2020/08/no-lie-is-too-big-for-journalists/
Greenland ice loss..LOL… more puerile meaningless bluster from griffool, the climate change denier.
SMB is average this year, and the tiny losses due to the partial recovery from the 1970s COLD era are meaningless
Greenland ice area is still way above what they have been for most of the last 10,000 years
Get an education griffool, so you don’t continue to make an baboon’s a*se of yourself.
The 1970’s had the strongest solar wind conditions of the space age. That drove a colder AMO, which cools the Arctic, increases low cloud cover, and slows continental glacier retreat. Since 1995 the reverse has occurred, with weaker solar wind driving a warmer AMO, and which is why the sea level is normally higher during centennial solar minima.
https://notrickszone.com/2019/12/05/cartology-affirms-relative-sea-levels-were-the-same-or-higher-than-now-during-the-little-ice-age/
Ummm… Griffter,
The climate-driven ice sheet loss has been ‘worst’ since about 13,000 years ago, when naturally (and thankfully!) the climate started warming and mile thick glaciers spanning the northern USA and Canada began to melt. All natural climate change… and continuing today, naturally. The Null Hypothesis holds!
Have a rainbow day!
At the same time, lots of parking lots, roads, houses were built and lots of forests got cleared to make more farmland. All that makes rainfall just go downriver, instead of staying in the aquifer for a month or seven.
On the other hand, much more farmland needs irrigations, so much that some rivers run dry. Add swimming pools and lawns and evaporation…
So many variables, but sure, the Graudian picks one and cries ‘Wolf’
Sorry, the Beeb, not the Graudian
I wonder how many millimeters of sea level rise could be mitigated by completing the Auburn Dam-
https://en.wikipedia.org/wiki/Auburn_Dam
It would certainly help mitigate black outs in the foothills.
“The rate of global-mean sea-level rise since 1900 has varied over time, but the contributing factors are still poorly understood”
As if the world didn’t exist before 1900. Way to cherry pick. Why not start with the end of the last glaciation?