
The basic circulation is well known but it requires accurate long-term records including sea level rise and terrestrial water storage including, aquifers, river flow, shrinking lakes and melting ice to understand how rising temperatures are effecting the moisture of the soil on a planet wide scale.
The research has shown a dramatic depletion of soil moisture which, in some areas, would require ten years of excessive rain to make good the loss, which is unlikely to happen.
The GRACE satellite program, which started in 2002, is a German built satellite funded and operated by NASA , is able to measure the changing mass of liquids and ice so that it can measure the reducing amount of oil in the Saudi oil fields, or the state of the Ogallala aquifer in the USA and the ice loss in Greenland.
What the research has discovered is that there has been a massive transfer of water from the land to the sea starting, most noticeably in 2000 when in two years there was a water loss of 1614 gigatonnes equivalent to 4.5 mm of sea level rise and, in an irregular pattern, this has continued. In the period 1993 to 1999 sea level was rising at 2.5 mm a year, during 2000 to 2010 the rise was averaging 3.4 mm a year, from 2010 to2021 it was 4.8 mm a year and in 2024 it reached an alarming 5.9 mm a year. Most of this came for water heat expansion and ice melting but the amount being lost from the land has alarming consequences in terms of drought and water shortages.
Water loss across the planet is not even, with places like the Central Plains of the US, the Amazon, China and central Asia suffering the worst but, surprisingly, Queensland, the West coast of India and some other areas gain water.
New Zealand is losing 192 million tonnes of topsoil each year, mostly from pastures where the land has been burnt off for sheep farming and land slips occur, and if you put that together with water loss due to heat and changes in rainfall our farmers are going to have a difficult time and we might wonder whether the planning of our reservoirs for drinking water are going to be sufficient, bearing in mind how far we are behind in our infrastructure.
Heavy rainfall and floods make good television, but drought is an insidious, long term, silent killer with failing crops, dying trees and drying rivers and lakes a steady reminder of the consequences.