Latest Momentous Discovery – The “Parched” Earth Is Getting Wetter!
By Paul Homewood
h/t James Grant Makin
Back in February, this paper appeared:
As glaciers melt due to climate change, the increasingly hot and parched Earth is absorbing some of that water inland, slowing sea level rise, NASA experts said Thursday.
Satellite measurements over the past decade show for the first time that the Earth’s continents have soaked up and stored an extra 3.2 trillion tons of water in soils, lakes and underground aquifers, the experts said in a study in the journal Science.
This has temporarily slowed the rate of sea level rise by about 20 percent, it said.
"We always assumed that people’s increased reliance on groundwater for irrigation and consumption was resulting in a net transfer of water from the land to the ocean," said lead author J.T. Reager of NASA’s Jet Propulsion Laboratory.
"What we didn’t realize until now is that over the past decade, changes in the global water cycle more than offset the losses that occurred from groundwater pumping, causing the land to act like a sponge—at least temporarily."
The global water cycle involves the flow of moisture, from the evaporation over the oceans to the fall of precipitation, to runoff and rivers that lead back into the ocean.
Just how much effect on sea level rise this kind of land storage would have has remained unknown until now because there are no land-based instruments that can measure such changes planet-wide.
An artist’s depiction of the NASA GRACE satellites and the Earth’s gravity field. Credit: NASA/JPL
The latest data came from a pair of NASA satellites launched in 2002—known as the Gravity Recovery and Climate Experiment (GRACE).
Researchers learned that the "water gains over land were spread globally, but taken together they equal the volume of Lake Huron, the world’s seventh largest lake," said a NASA statement.
Researchers said the findings will help scientists better calculate sea level changes in the years ahead.
Map of trends in water storage over the continents as measured by the GRACE satellites. Credit: J.T. Reager, NASA /JPL
"These results will lead to a refinement of global sea level budgets, such as those presented in the Intergovernmental Panel on Climate Change (IPCC) reports, which acknowledge the importance of climate-driven changes in hydrology, but have been unable to include any reliable estimate of their contribution to sea level changes," said senior author Jay Famiglietti, a professor at the University of California, Irvine.
"But we’ll need a much longer data record to fully understand the underlying cause of the patterns and whether they will persist."
Updated ocean mass budget. Credit: J.T. Reager, NASA /JPL
Apparently the Earth can be hot and parched, while at the same time it is receiving more rainfall. Put another way, mankind is taking out roughly the same amount from the Earth’s lakes, rivers and aquifers, as is being replenished, at least in global, if not regional, terms.
Notice on the map how areas like the Sahel, East Africa and the Amazon are said to have seen an increase in water storage, contrary to popular myth.
The paper is here.
What makes the paper interesting though was this second study, which appeared three months later:
Groundwater extraction and other land water contribute about three times less to sea level rise than previous estimates, according to a new study published in the journal Nature Climate Change. The study does not change the overall picture of future sea level rise, but provides a much more accurate understanding of the interactions between water on land, in the atmosphere, and the oceans, which could help to improve future models of sea level rise.
"Projecting accurate sea level rise is important, because rising sea level is a threat to people who live near the ocean and in small islands," explains IIASA researcher Yoshihide Wada, who led the study. "Some low-lying areas will have more frequent flooding, and very low-lying land could be submerged completely. This could also damage substantially coastal infrastructure."
Sea level has risen 1.7 mm per year over the 20th and the early 21st century, a trend that is expected to continue as climate change further warms the planet. Researchers have attributed the rising seas to a combination of factors including melting ice caps and glaciers, thermal expansion (water expands as it gets warmer), and the extraction of groundwater for human use.
Land water contributions are small in comparison to the contribution of ice melt and thermal expansion, yet they have been increasing, leading to concerns that this could exacerbate the problem of sea level rise caused by climate change.
However, much uncertainty remains about how much different sources contribute to sea level rise. In fact, sea level has actually risen more than researchers could account for from the known sources, leading to a gap between observed and modeled global sea-level budget.
Previous studies, including estimates used in the IPCC Fifth Assessment Report, had assumed that nearly 100% of extracted groundwater ended up in the ocean. The new study improves on previous estimates by accounting for feedbacks between the land, ocean, and atmosphere. It finds that number is closer to 80%. That means that the gap between modeled and observed sea level rise is even wider, suggesting that other processes are contributing more water than previously estimated.
"During the 20th century and early 21st century, cumulative groundwater contribution to global sea level was overestimated by at least 10 mm," says Wada. In fact, the new study shows that from 1971 to 2010, the contribution of land water to global sea level rise was actually slightly negative — meaning that more water was stored in groundwater and also due to reservoir impoundment behind dams. From 1993 to 2010, the study estimates terrestrial water as contributing positive 0.12 mm per year to sea level rise.
In other words, this study came to similar conclusions, that net extraction of groundwater was much less then originally thought.
But note this comment:
In fact, sea level has actually risen more than researchers could account for from the known sources, leading to a gap between observed and modeled global sea-level budget.
The discovery that we have not been busy extracting our groundwater reserves, as enviro-alarmists like to claim, actually means that this gap is now larger. The theoretical contributions to sea level rise, from thermal expansion, melting glaciers and groundwater do not account for all of the sea level rise, which is currently claimed.
While climate grant funded researchers tie themselves in knots trying to explain this conundrum, there is actually a very simple, eloquent and convincing explanation – sea level rise has actually been overestimated.