Grade Expectations. Review of 1990s Water Projections for 2025 Finds Withdrawals Overestimated and Calls the Results Well Aligned

Charles Rotter On October 28, WIREs Climate Change published Early Climate Impact Assessments Targeted 2025—How Did They Perform for Global Water Resources? by Declan Conway, Rachel James, Roger Calow, Kate Gannon and Jim Hall. It is a rare thing in this field, a look back at projections whose target date has actually arrived. The two papers under review are Arnell (1999)00017-5) in Global Environmental Change and Vörösmarty et al. (2000) in Science, the first global water models to use 2025 as ...

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7 Comments

Laws of Nature

November 1, 2026 10:57 am

I cant read this paywalled article yet, but I happen to know that there was a massive discrepancy of the physics (in particular cloud related) and resolution between CMIP6 and any older model, which makes any older model or conclusion drawn from it seem very irrelevant.

(At least until this discrepancy is resolved for the old published findings – but so far there is not the slightest attempt by any of the climate scientists to correct their old findings even so they all know without any doubt that those were not correct! )

Whetten Robert L

Reply to Laws of Nature

November 1, 2026 6:37 pm

there is not the slightest attempt by any of the climate scientists to correct their old findings…

They’ve moved on already, like a Hit-&-Run Driver fleeing the scene of the accident.

Whetten Robert L

Reply to Laws of Nature

November 1, 2026 9:18 pm

Even now, after six (6!) decades of General-Circulation Modeling (GCMs), they have to admit that they cannot get the water cycle (Hydrology) quite right.

Usually in an oblique or dismissive manner, such as ‘Cloud Parametrization needs tweaking’… but revelatory nonetheless.

Can’t one just come out & state plainly that this (Hydrology Fail) is prominent among the original sins (erroneous assumptions) in the Carney Report (~ ’79)?

Even an alert schoolchild might enquire, ‘Why assume that the Relative Humidity (RH) will remain unchanged?’ (invariant / constant) when the sea-surface temperature (SST) varies.

As evidenced in the actual meteorological records, the RH is not maintained, neither is the Absolute Humidity (water vapor mole-fraction) unchanged, as the SST varies from year to year, but rather some unknown quantity betwixt the two.

To treat hydrology, or rather to dismiss it, as a pedestrian issue — somehow beneath the dignity of the specialists in optics – spectroscopy – radiative thermodynamics, may seem retrospectively as a colossal error in judgment, from which today’s Climate Science (so-called) may never recover.

Lest anyone think it remains a too-simple-for-[us] problem to (re)solve, don’t forget that water (hydrology) is implicated in the ‘Bio-Physics’ along with Photochemistry & elevated-CO2 ‘fertilization’. Enhanced retention of water in healthy soils and microbes, as well as in the more obvious ‘leaf index’ and its oceanic equivalent … may factor into any water ‘missing’ from the balance-sheet. As Prof F. Dyson was insistent upon, these factors frequently lack adequate metrology, as compared to sea-land-sky metrics.

It’s not that no-one is aware or working on this! Not-A-Climate-Scientists such as Meteorologist J. Bastardi (in his own quirky way) have been insisting on the novel (or re-emergent) level of atmospheric water-content, especially extra-tropical zones that have not seen such levels in the instrumental record.

Rather it is that they cannot do this heavy-lifting alone, or intermittently (after their day-job work is done). It requires attention & staying-power to see it thru to some enduring resolution.

Thanks for reading, and for tolerating many faults, — RLW (from Chennai, IIT-Madras)

Jeff Alberts

November 1, 2026 12:21 pm

“and are cited most by the IPCC and the World Bank:”

That tells you pretty much all you need to know.

Mike Webb

November 1, 2026 4:35 pm

So, don’t let my lying eyes deceive me into thinking there is a draught outside.

Phillip Chalmers

November 1, 2026 11:56 pm

Firstly, I cannot see any justification or use whatsoever for the spending of one single rupee on the initial report or the checking of the validity of the predictions.
It is peppered with the use of assumed AGW as an explanation
The lower than expected “water stress” is unexplained.
No mention was made of the greening of the planet, a proxy of “less need for water to grow the same amount of food” – the higher carbon dioxide allowing much of the photosynthesis to be done with less loss of water from each pore in every leaf.

Fran

November 2, 2026 9:51 am

Is not the depletion of aquafers a serious problem in many regions?

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