A new study warns that global declines in soil moisture in the 21st century could mark a “permanent” shift in the world’s water cycle.
Combining data from satellites, sea level measurements and observations of “polar motion”, the research shows how soil moisture levels have decreased since the year 2000.
The findings, published in Science, suggest the decline is primarily driven by an increasingly thirsty atmosphere as global temperatures rise, as well as shifts in rainfall patterns.
Consequently, the researchers warn the observed changes are likely to be “permanent” if current warming trends continue.
An accompanying perspective article says the study provides “robust evidence” of an “irreversible shift” in terrestrial water sources under climate change.
The drying out of soil “increases the severity and frequency” of major droughts, with consequences for humans, ecosystems and agriculture, explains Dr Benjamin Cook, an interdisciplinary Earth system scientist working at the NASA Goddard Institute for Space Studies and Columbia University, who was not involved in the research.
He tells Carbon Brief:
“Droughts are one of the most impactful, expensive natural hazards out there, because they are typically persistent and long lasting. Everything needs water – ecosystems need water, agriculture needs water. People need water. If you don’t have enough water – you’re in trouble.”
Drying soil
Every year, around 6tn tonnes of water cycles through Earth’s land surface. When rain falls on land it gets held up in soil, wetlands, groundwater, lakes and reservoirs on its journey back to the oceans.
Soil moisture forms a critical part of the Earth’s system, helping to irrigate soil, cycle nutrients and regulate the climate.
The amount of water contained in the soil is sensitive to a range of factors, including changes in rainfall, evaporation, vegetation and climate – as well as human activity, such as intensive agriculture.
The research points to a “gradual decline” in soil moisture levels in the 21st century, kickstarted by a period of “sharp depletion” in the three years over 2000-02.
Specifically, the researchers find the depletion of soil moisture resulted in a total loss of 1,614bn tonnes (gigatonnes, or Gt) of water over 2000-02 and then 1,009Gt between 2002 and 2016.
(For context, ice loss in Greenland resulted in 900Gt of water loss over 2002-06.)
Soil moisture has not recovered as of 2021, according to the research, and is unlikely to pick up under present climate conditions.
Joint-lead author Prof Dongryeol Ryu, professor of hydrology and remote sensing at the University of Melbourne, explains to Carbon Brief:
“We observed a stepwise decline [in soil moisture] twice in the past two decades, interspersed within a continuously declining trend in soil moisture. We haven’t seen this trend earlier, so that is why this is very concerning.”
Ryu explains the decision to analyse changes to soil moisture on a global scale meant the researchers could confirm trends difficult to see in smaller geographic datasets:
“The unique thing we found through analysing these larger-scale measures is that – even if we have seen widely fluctuating ups and downs in precipitation and increasing temperature – the total water contained in the soil, as soil moisture and groundwater, has been declining gradually from around the beginning of this century.“
The maps below illustrate soil moisture changes in 2003-07 and 2008-12 against a 1995-99 baseline, as estimated by the ERA5-Land reanalysis dataset. The areas marked on the map in brown saw a drop in soil moisture and the areas marked in blue an increase in soil moisture.
The top map shows soil moisture depletion across large regions in eastern and central Asia, central Africa and North and South America over 2003-07. The lower map shows that “replenishment” in the years that followed occurred in relatively small parts of South America, India, Australia and North America.
Climate change
Ryu says the researchers “suspect that increasing temperature played an important role” in the decline in terrestrial water storage and soil moisture in the 21st century.
The study points to two factors driving gradual depletion of soil moisture over the last quarter century: fluctuations to rainfall patterns and increasing “evaporative demand”.
Evaporative demand refers to the atmosphere’s “thirst” for water, or how much moisture it can take from the land, vegetation and surface water.
Studies have highlighted how global evaporative demand has been increasing over the last two decades globally, impacting water availability, hurting crops and causing drought.
The new study notes that “increasing evaporative demand driven by a warming climate” suggests a “more consistent and widespread trend toward drying as temperatures rise”.
Ryu says the “very unusual” drop in water moisture observed over 2000-02 could be attributed to low levels of rainfall globally, which coincided with the “period when evaporative demand started increasing”.
Another – less pronounced – period of rapid soil moisture decline seen over 2015-16 can be attributed to droughts triggered by the 2014-16 El Niño event, Ryu notes.
Ryu says the study findings indicate that soil moisture can no longer bounce back from a dry year, as it has in the past:
“It used to be that when precipitation goes up again, we recover water in the soil. But because of this increasing evaporative demand, once we have strong El Niño years – which lead to much less rainfall for a year or two – it seems that we are not recovering the water fully because of increasing evaporative demand. Because of that – even if we have a wet year following dry years – the water in the soil doesn’t seem to recover.”
Cross-validation
Measuring changes in global soil moisture has historically presented a challenge to scientists, given the lack of comprehensive and direct observations of water in soil.
The researchers attempt to reduce this uncertainty by corroborating the ERA5-Land reanalysis dataset from the European Centre for Medium-Range Weather Forecasts (ECMWF) with three geophysical measurement datasets.
ERA5’s land surface modelling system uses meteorological and other input data to estimate water within the upper few metres of the soil.
These figures were compared with data collected by the Gravity Recovery and Climate Experiment (GRACE) mission – a joint satellite mission between NASA and the German Aerospace Center.
Running since 2002, the GRACE mission tracks changes to the Earth’s gravity by collecting data on groundwater depletion, ice sheet loss and sea level rise. These observations have revealed a persistent loss of water from land to the ocean.
The scientists also cross-reference the ERA5 reanalysis data with a century-old dataset that measures fluctuations in the rotation of the Earth as the distribution of mass on the planet changes.
(The redistribution of ice and water, such as melting ice sheets and depleting groundwater, causes the planet to wobble as it spins and its axis to shift slightly. This is known as “polar motion”.)
The third set of measurements the scientists use is global mean sea level height, which is collected by satellites.
To extract soil moisture changes from this set of data, the researchers subtracted other components of sea level rise from the overall total – including Greenland ice melt, Antarctica ice melt, the impact of increasing sea surface temperature (which expands water volume) and the contribution of groundwater.
This process of elimination left researchers with an estimate of the contribution of soil moisture to global sea level rise.
The study notes that both the sea surface height and polar motion observations “support the conclusion that the abrupt change in soil moisture is genuine”.
Ryu says using global average sea level rise and “Earth wobble” to track water redistribution on land is the “main innovation” applied in the paper.
He adds the value of “reverse engineering” the ERA5 dataset is to understand how to enhance land surface modelling in the future:
“By explaining all the contributing factors to this measurement, you can understand the process. And if you understand the process, you can actually predict what’s going to happen in the future if any of these factors change in a certain manner.”
NASA’s Dr Cook says the “corroborating evidence” supplied by the paper offers a “really strong case that there has been a large-scale decline in soil moisture in recent decades”.
However, he says the relatively short reference period of the study means that identifying the cause of the decline is less clear cut:
“Whether [the decline] is permanent or not is much more uncertain…On these timescales, internal natural variability can be really, really strong. Attributing this decline to something specific – either climate change or internal variability – is much much more difficult.”
Sea level rise
A notable finding in the study’s sea level rise analysis is that terrestrial water storage may have been the dominant driver of sea level rise in the early 21st century.
Specifically, the paper notes that the decline in terrestrial water storage over 2000-02 – when soil moisture plummeted – led to global average sea level rise of almost 2mm annually.
The researchers note this rate of sea level rise is “unprecedented” and “significantly higher” than the rate of sea level rise attributed to Greenland ice mass loss, which they note is approximately 0.8mm a year.
Prof Reed Maxwell, a professor at the High Meadows Environmental Institute at Princeton University, who was also not involved in the study, says the researchers’ efforts to compare soil moisture with other global water stores was “novel” and “opens the door to future study of a more holistic global water balance”.
‘Creeping disaster’
The paper notes that land surface and hydrological models require “substantial improvement” to accurately simulate changes in soil moisture in changing climate.
Current models do not factor the impacts of agricultural intensification, nor the ongoing “greening” of semi-arid regions – both of which “may contribute” to a further decline in soil moisture, it states.
Writing in a perspectives article published in Science, Prof Luis Samaniego from the department of computational hydrosystems at the Helmholtz Centre for Environmental Research says that it is “essential” that next-generation models incorporate human-caused influences such as farming, large dams and irrigation systems.
The study posits that the “innovative methods” for estimating changes in global soil moisture presented in the study provide opportunities to “improve the present state of modelling at global and continental scales”.
More broadly, advances in scientific understanding of changes to soil moisture can help improve the world’s preparedness for drought.
Drought is often described as a “creeping disaster” – because by the time it is identified, it is usually already well under way,
Paper author Ryu explains:
“Unlike a flood and heatwaves, drought comes very very slowly – and has prolonged and delayed consequences. We better be prepared earlier than later, because once drought comes you can expect a long period of consequences.”
Dr Shou Wang, associate professor at the Hydroclimate Extremes Lab and the Hong Kong Polytechnic University, who was not involved in the study, says the research findings are “crucial” for advancing understanding of the “potential drivers and dynamics” of “unprecedented hydrological extremes in a warming climate”. He tells Carbon Brief:
“This is breakthrough work that uncovers the drivers of hydrological regime changes, which are leading to unprecedented hydrological extremes such as compound and consecutive drought-flood events.”
The post Global soil moisture in ‘permanent’ decline due to climate change appeared first on Carbon Brief.
Global soil moisture in ‘permanent’ decline due to climate change
Climate Change
DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Blazing heat hits Europe
FANNING THE FLAMES: Wildfires “fanned by a heatwave and strong winds” caused havoc across southern Europe, Reuters reported. It added: “Fire has affected nearly 440,000 hectares (1,700 square miles) in the eurozone so far in 2025, double the average for the same period of the year since 2006.” Extreme heat is “breaking temperature records across Europe”, the Guardian said, with several countries reporting readings of around 40C.
HUMAN TOLL: At least three people have died in the wildfires erupting across Spain, Turkey and Albania, France24 said, adding that the fires have “displaced thousands in Greece and Albania”. Le Monde reported that a child in Italy “died of heatstroke”, while thousands were evacuated from Spain and firefighters “battled three large wildfires” in Portugal.
UK WILDFIRE RISK: The UK saw temperatures as high as 33.4C this week as England “entered its fourth heatwave”, BBC News said. The high heat is causing “nationally significant” water shortfalls, it added, “hitting farms, damaging wildlife and increasing wildfires”. The Daily Mirror noted that these conditions “could last until mid-autumn”. Scientists warn the UK faces possible “firewaves” due to climate change, BBC News also reported.
Around the world
- GRID PRESSURES: Iraq suffered a “near nationwide blackout” as elevated power demand – due to extreme temperatures of around 50C – triggered a transmission line failure, Bloomberg reported.
- ‘DIRE’ DOWN UNDER: The Australian government is keeping a climate risk assessment that contains “dire” implications for the continent “under wraps”, the Australian Financial Review said.
- EXTREME RAINFALL: Mexico City is “seeing one of its heaviest rainy seasons in years”, the Washington Post said. Downpours in the Japanese island of Kyushu “caused flooding and mudslides”, according to Politico. In Kashmir, flash floods killed 56 and left “scores missing”, the Associated Press said.
- SOUTH-SOUTH COOPERATION: China and Brazil agreed to “ensure the success” of COP30 in a recent phone call, Chinese state news agency Xinhua reported.
- PLASTIC ‘DEADLOCK’: Talks on a plastic pollution treaty have failed again at a summit in Geneva, according to the Guardian, with countries “deadlocked” on whether it should include “curbs on production and toxic chemicals”.
15
The number of times by which the most ethnically-diverse areas in England are more likely to experience extreme heat than its “least diverse” areas, according to new analysis by Carbon Brief.
Latest climate research
- As many as 13 minerals critical for low-carbon energy may face shortages under 2C pathways | Nature Climate Change
- A “scoping review” examined the impact of climate change on poor sexual and reproductive health and rights in sub-Saharan Africa | PLOS One
- A UK university cut the carbon footprint of its weekly canteen menu by 31% “without students noticing” | Nature Food
(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)
Captured
Factchecking Trump’s climate report
A report commissioned by the US government to justify rolling back climate regulations contains “at least 100 false or misleading statements”, according to a Carbon Brief factcheck involving dozens of leading climate scientists. The report, compiled in two months by five hand-picked researchers, inaccurately claims that “CO2-induced warming might be less damaging economically than commonly believed” and misleadingly states that “excessively aggressive [emissions] mitigation policies could prove more detrimental than beneficial”80
Spotlight
Does Xi Jinping care about climate change?
This week, Carbon Brief unpacks new research on Chinese president Xi Jinping’s policy priorities.
On this day in 2005, Xi Jinping, a local official in eastern China, made an unplanned speech when touring a small village – a rare occurrence in China’s highly-choreographed political culture.
In it, he observed that “lucid waters and lush mountains are mountains of silver and gold” – that is, the environment cannot be sacrificed for the sake of growth.
(The full text of the speech is not available, although Xi discussed the concept in a brief newspaper column – see below – a few days later.)
In a time where most government officials were laser-focused on delivering economic growth, this message was highly unusual.
Forward-thinking on environment
As a local official in the early 2000s, Xi endorsed the concept of “green GDP”, which integrates the value of natural resources and the environment into GDP calculations.
He also penned a regular newspaper column, 22 of which discussed environmental protection – although “climate change” was never mentioned.
This focus carried over to China’s national agenda when Xi became president.
New research from the Asia Society Policy Institute tracked policies in which Xi is reported by state media to have “personally” taken action.
It found that environmental protection is one of six topics in which he is often said to have directly steered policymaking.
Such policies include guidelines to build a “Beautiful China”, the creation of an environmental protection inspection team and the “three-north shelterbelt” afforestation programme.
“It’s important to know what Xi’s priorities are because the top leader wields outsized influence in the Chinese political system,” Neil Thomas, Asia Society Policy Institute fellow and report co-author, told Carbon Brief.
Local policymakers are “more likely” to invest resources in addressing policies they know have Xi’s attention, to increase their chances for promotion, he added.
What about climate and energy?
However, the research noted, climate and energy policies have not been publicised as bearing Xi’s personal touch.
“I think Xi prioritises environmental protection more than climate change because reducing pollution is an issue of social stability,” Thomas said, noting that “smoggy skies and polluted rivers” were more visible and more likely to trigger civil society pushback than gradual temperature increases.
The paper also said topics might not be linked to Xi personally when they are “too technical” or “politically sensitive”.
For example, Xi’s landmark decision for China to achieve carbon neutrality by 2060 is widely reported as having only been made after climate modelling – facilitated by former climate envoy Xie Zhenhua – showed that this goal was achievable.
Prior to this, Xi had never spoken publicly about carbon neutrality.
Prof Alex Wang, a University of California, Los Angeles professor of law not involved in the research, noted that emphasising Xi’s personal attention may signal “top” political priorities, but not necessarily Xi’s “personal interests”.
By not emphasising climate, he said, Xi may be trying to avoid “pushing the system to overprioritise climate to the exclusion of the other priorities”.
There are other ways to know where climate ranks on the policy agenda, Thomas noted:
“Climate watchers should look at what Xi says, what Xi does and what policies Xi authorises in the name of the ‘central committee’. Is Xi talking more about climate? Is Xi establishing institutions and convening meetings that focus on climate? Is climate becoming a more prominent theme in top-level documents?”
Watch, read, listen
TRUMP EFFECT: The Columbia Energy Exchange podcast examined how pressure from US tariffs could affect India’s clean energy transition.
NAMIBIAN ‘DESTRUCTION’: The National Observer investigated the failure to address “human rights abuses and environmental destruction” claims against a Canadian oil company in Namibia.
‘RED AI’: The Network for the Digital Economy and the Environment studied the state of current research on “Red AI”, or the “negative environmental implications of AI”.
Coming up
- 17 August: Bolivian general elections
- 18-29 August: Preparatory talks on the entry into force of the “High Seas Treaty”, New York
- 18-22 August: Y20 Summit, Johannesburg
- 21 August: Advancing the “Africa clean air programme” through Africa-Asia collaboration, Yokohama
Pick of the jobs
- Lancaster Environment Centre, senior research associate: JUST Centre | Salary: £39,355-£45,413. Location: Lancaster, UK
- Environmental Justice Foundation, communications and media officer, Francophone Africa | Salary: XOF600,000-XOF800,000. Location: Dakar, Senegal
- Politico, energy & climate editor | Salary: Unknown. Location: Brussels, Belgium
- EnviroCatalysts, meteorologist | Salary: Unknown. Location: New Delhi, India
DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org.
This is an online version of Carbon Brief’s weekly DeBriefed email newsletter. Subscribe for free here.
The post DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report appeared first on Carbon Brief.
DeBriefed 15 August 2025: Raging wildfires; Xi’s priorities; Factchecking the Trump climate report
Climate Change
New York Already Denied Permits to These Gas Pipelines. Under Trump, They Could Get Greenlit
The specter of a “gas-for-wind” compromise between the governor and the White House is drawing the ire of residents as a deadline looms.
Hundreds of New Yorkers rallied against new natural gas pipelines in their state as a deadline loomed for the public to comment on a revived proposal to expand the gas pipeline that supplies downstate New York.
New York Already Denied Permits to These Gas Pipelines. Under Trump, They Could Get Greenlit
A “critical assessment” report commissioned by the Trump administration to justify a rollback of US climate regulations contains at least 100 false or misleading statements, according to a Carbon Brief factcheck involving dozens of leading climate scientists.
The report – “A critical review of impacts of greenhouse gas emissions on the US climate” – was published by the US Department of Energy (DoE) on 23 July, just days before the government laid out plans to revoke a scientific finding used as the legal basis for emissions regulation.
The executive summary of the controversial report inaccurately claims that “CO2-induced warming might be less damaging economically than commonly believed”.
It also states misleadingly that “excessively aggressive [emissions] mitigation policies could prove more detrimental than beneficial”.
Compiled in just two months by five “independent” researchers hand-selected by the climate-sceptic US secretary of energy Chris Wright, the document has sparked fierce criticism from climate scientists, who have pointed to factual errors, misrepresentation of research, messy citations and the cherry-picking of data.
Experts have also noted the authors’ track record of promoting views at odds with the mainstream understanding of climate science.
Wright’s department claims the report – which is currently open to public comment as part of a 30-day review – underwent an “internal peer-review period amongst [the] DoE’s scientific research community”.
The report is designed to provide a scientific underpinning to one flank of the Trump administration’s plans to rescind a finding that serves as the legal prerequisite for federal emissions regulation. (The second flank is about legal authority to regulate emissions.)
The “endangerment finding” – enacted by the Obama administration in 2009 – states that six greenhouse gases are contributing to the net-negative impacts of climate change and, thus, put the public in danger.
In a press release on 29 July, the US Environmental Protection Agency said “updated studies and information” set out in the new report would “challenge the assumptions” of the 2009 finding.
Carbon Brief asked a wide range of climate scientists, including those cited in the “critical review” itself, to factcheck the report’s various claims and statements.
The post Factcheck: Trump’s climate report includes more than 100 false or misleading claims appeared first on Carbon Brief.
https://www.carbonbrief.org/factcheck-trumps-climate-report-includes-more-than-100-false-or-misleading-claims/
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