Experts welcomed the data with hope — and
caution. Tropical forest loss is still 46% higher than ten years ago.
Today’s newsletter looks at how Brazil’s 2023 anti-deforestation plan is
starting to bear fruit. We also bring you the latest on how climate change impacted Europe’s temperatures, glaciers and oceans last year.
Deforestation win
Tropical forest loss declined significantly last year, falling 36% after reaching a record level in 2024. Still, the world lost 4.3 million hectares (10.6 million acres) of rainforest — an area roughly the size of Denmark, or more than 11 soccer fields every minute.
New
data from the University of Maryland, published through the World
Resources Institute’s Global Forest Watch, shows that the loss of
primary — or mature and largely undisturbed — humid tropical forests
slowed down in 2025. But it was still 46% higher than a decade earlier,
and last year saw a relative lull in wildfires after an exceptionally
bad fire year in 2024. Blazes are increasing in the tropics due to
warmer temperatures and more severe droughts
Outside the tropics, the
climate signal was starker. Wildfires burned 5.3 million hectares in
Canada, making 2025 the country’s second-worst fire year on record. In
France, fire-driven tree-cover loss was the most severe on record, seven
times higher than in the previous year.
The
analysis uses a broad definition of forest loss that includes not just
deforestation for agriculture but also timber harvesting and natural
disturbances to forests.
At
the COP26 climate summit in 2021, more than 100 countries pledged to
halt and reverse forest loss by 2030. The world remains far from that
goal as agricultural expansion and fires continue to destroy important
biodiversity hotspots and carbon sinks. Forest loss in 2025 was still
about 70% too high for countries to be on track for the deadline,
according to the World Resources Institute, or WRI.
“Achieving
this goal in the coming years will not be easy as forests become more
vulnerable to climate change, and as humanity’s demand for food, fuel
and materials from forests and the lands they stand on continues to
grow,” said Elizabeth Goldman, co-director of Global Forest Watch at
WRI.
Smoke rises during a fire in the Brazilian Amazon
Photographer: Leonardo Carrato/Bloomberg
Brazil, which encompasses
two-thirds of the Amazon, the world’s largest rainforest, recorded the
largest absolute area of primary forest loss. But it cut that loss by
42% from the previous year. The report attributes the decline to
stronger environmental policy and enforcement under President Luiz
Inácio Lula da Silva.
The
improvement stands in stark contrast to 2024, when Brazil’s Amazon
suffered its worst drought on record, fueling unprecedented forest
fires.
André Lima, Brazil’s
secretary for deforestation control, said in a phone interview that the
country’s forest policy rests on “two agendas that are intertwined” —
curbing deforestation and controlling fires. He said the government
relaunched the federal anti-deforestation plan in 2023 under Lula and is
now beginning to see results. Citing Brazil’s official data, Lima said
Amazon deforestation fell 50% in 2025 compared with 2022.
Public servants working for the Tokyo
metropolitan government are being encouraged to swap their suits for
shorts this summer to combat sweltering heat and rising energy costs
caused by the US-Israel war on Iran.
Inspired by the country’s Cool Biz energy-saving initiative, Tokyo officials hope the measure will cut dependence on air conditioning.
Cool
Biz, launched by the environment ministry in 2005, initially encouraged
bureaucrats to dispense with ties and jackets, but has so far stopped
short of allowing them to display their bare legs in front of
colleagues.
Japan and other countries in Asia are growing anxious
about the economic effects of the conflict in the Middle East, amid
rising oil prices and shortages of petroleum products such as jet fuel.
Resource-poor Japan
is particularly vulnerable to a prolonged war as it depends on the
Middle East for 90% of its oil imports, most of which pass through the
strait of Hormuz. About 20% of the natural gas used in South Korea comes
via the same route.
Vietnam, South Korea and
other countries have taken steps to ration energy use, while other Asian
nations have encouraged government officials to work from home or
reduced the length of the working week. In Seoul, authorities have urged
residents to make short trips on foot or by bicycle.
Japan has already tapped into its large strategic oil reserves,
with local media reporting on Friday that it plans to release a further
20 days’ worth from 1 May. It is also sourcing oil imports from
suppliers that do not use the strait of Hormuz.
Experts
have warned that if shipping in the vital waterway doesn’t return to
normal soon, the world’s fourth-biggest economy will eventually face a
crude oil shortage. That could force businesses and households to make
more drastic cuts in petrol and electricity usage reminiscent of those
introduced during the oil shocks of the 1970s.
The
threat of an energy crunch had been “one of the factors” in allowing
Tokyo government staff to wear casual clothes to work, Agence
France-Presse said, adding that some employees had been spotted in
shorts, T-shirts and short-sleeved blouses since the initiative’s launch
this week to coincide with the start of Japan’s heatstroke warning
system.
“I was a bit nervous, but it’s very
comfortable, and I feel like it’ll improve my work efficiency,” a
metropolitan government official who was wearing shorts to the office
for the first time told the Yomiuri Shimbun newspaper. “As it gets even
hotter, I’d like to come in earlier and work from home as well.”
Citing
“a severe outlook for electricity supply and demand,” Tokyo’s governor,
Yuriko Koike, who as environment minister was behind the Cool Biz
campaign two decades ago, told reporters: “We encourage cool attire that
prioritises comfort, including polo shirts, T-shirts and sneakers and –
depending on job responsibilities – shorts”.
War notwithstanding, Japanese employers have been forced to rethink old rules on workplace attire as a result of the climate crisis. Last year, the country endured its hottest summer since records began in 1898, according to the meteorological agency.
Now
that it is no longer unheard of for temperatures to rise to 40C or
above, the agency last week announced a new extreme weather event: kokusho, or “cruelly hot”.
Even in his final months, he counted the days
until the cherry blossoms. Prof Yasuyuki Aono of Osaka Metropolitan
University spent his career gathering data on the spring flowering dates
of cherry trees in Japan in what is one of the world’s longest climate records tracking a seasonal occurrence.
Using
sources dating as far back as the 9th century, he revealed that cherry
tree flowerings have occurred progressively earlier in recent decades – a
now famous marker of climate change.
Last April, Aono posted a photo
to social media of his spreadsheet. He had just completed the 2025
entry, recording “4 [April]” as the peak flowering date for the
particular cherry tree species he tracked, the mountain cherry, or
Prunus jamasakura.
Below this, the next row
was already marked “2026” but Aono never got to fill it in. He died on 5
August last year, according to former colleagues contacted by the
Guardian.
Yasuyuki Aono learned old forms of Japanese so he could read 9th-century records. Photograph: Richard Primack
“You can very much see that he planned to
continue,” said Tuna Acisu, a data scientist at Our World in Data, an
online platform that publishes a chart based on Aono’s cherry tree data. “That made me a little bit emotional.”
Now, following a search
launched by Acisu last week – sparked by fears that no one would be
able to continue the 1,200-year cherry blossom record – a researcher in
Japan has stepped forward and offered to make formal observations of the
mountain cherry’s spring flowerings.
“He is
consulting the same sources as Prof Aono to get us this year’s cherry
blossom peak bloom and said he will confirm the date in the coming
days,” Acisu said. The researcher in question asked to remain anonymous
until the arrangement is finalised.
Acisu and
colleagues first realised that something may have happened to Aono when
they noticed in January that his university web page was no longer
active. They then learned that he had died and that no other researcher
or institution had emerged to carry on his observations. Spring arrived
with no new mountain cherry data.
After Acisu
launched her campaign to find a new cherry blossom observer, she
received dozens of messages. “It’s really great to know that the dataset
is being continued,” she said, expressing her gratitude to the new
researcher. “I feel very relieved.”
Crucially, Acisu had sought a contact in Japan
who could continue tracking not only the same species of cherry, but
also in the same location: Arashiyama, Kyoto.
There
are other projects that monitor cherry tree flowerings around Japan,
since cherry bloom festivals are an important part of culture and
tourism in the country, but not this specific species. For example, the
Japan Weather Association monitors a different species: the Somei-yoshino cherry (Prunus x yedoensis), which was cultivated in the 19th century.
That Aono was able to compile flowering data for
the mountain cherry over a period spanning more than 1,200 years is what
gave his data series such significance, said Acisu.
Scientists have found the signature of climate change in a wide variety of other sources, including tree rings, plant pigments deposited in seabed sediments, and even temperature and humidity records jotted down by organ tuners in British churches.
Among the revelations made by Aono were the 2021
and 2023 peak flowering dates – they are the earliest in the entire
mountain cherry record, occurring on the 85th and 84th day of those
years, respectively.
Aono’s work on the
mountain cherry was “extremely important”, said Toshio Katsuki, a
dendrologist at the Forestry and Forest Products Research Institute in
Ibaraki prefecture, who added that efforts to continue recording the
same species’ spring flowering dates would be academically valuable.
Tourists wearing kimonos pose with cherry blossoms in Kyoto at the end of March this year. Photograph: Manami Yamada/Reuters
Richard Primack, a professor of biology at Boston
University, met Aono on a trip to Japan in 2006. Aono told him that he
had learned to read old forms of Japanese in order to build up his
dataset of mountain cherry flowering dates. In dusty historical
archives, Aono would find references to cherry blossom festivals in
Kyoto and, from that, was able to calculate the flowering dates for
specific years.
While some years are missing,
the earliest record he found dated to 812. “It was really quite an
amazing experience,” said Primack, remembering the meeting. “You just
realise how dedicated an individual he was.”
In a paper published earlier this month,
Primack and Katsuki described how flowering of the Somei-yoshino cherry
also appears to be affected by climate change in southern areas of
Japan. Data from 1965 to 2024 shows that milder winters were
increasingly causing the spring-flowering cherries to have “a kind of
bedraggled look, rather than a full, dazzling display,” said Primack.
“Many of the flower buds were falling off without opening.”
When Hurricane Michael, a
Category 5 storm, tore through Florida’s Tyndall Air Force Base in 2018,
it battered F-22 stealth fighter jets, destroyed hundreds of buildings
and churned up 700,000 cubic yards of debris. The total cost of the
damage approached $5 billion.
Now,
Tyndall is being rebuilt as a super-resilient “installation of the
future.” New buildings sit more than a foot above the ground, to remain
dry through 75 years of sea-level rise. Their roofs are designed to
withstand winds of up to 165 miles per hour. Manmade oyster reefs will
protect coasts by breaking up waves.
The
massive project will be 70% complete next year, said the officer
leading it, Col. Robert Bartlow, chief of the US Air Force Civil
Engineer Center Natural Disaster Recovery Division. “This is a first for
the Air Force,” he said, with large-scale, cutting-edge construction
taking place “on top of an existing base, while there was a continued
flying mission.”
Storms like Michael are
becoming more powerful and damaging as the world warms, and many
military installations are exposed to them and other climate hazards.
Still, Secretary of Defense Pete Hegseth vowed last year that the
Pentagon wouldn’t do any “climate change crap” on his watch. Biden-era
climate action plans were scrapped, and the 2025 National Security
Strategy invoked climate change only to label it a “disastrous”
ideology. Hegseth canceled nearly 100 research studies related to global
warming and security, which experts say will compound the loss of
climate knowledge across the federal government under President Donald
Trump.
“Because ‘climate’
is a dirty word, we’re not investing in that predictive capability,”
said Sherri Goodman, secretary general of the non-governmental
International Military Council on Climate and Security and, from 1993 to
2001, the US deputy undersecretary of defense for environmental
security.
But as Tyndall
shows, the Defense Department is still engaged on one front of the
climate fight: steeling its bases against the effects of a warming
atmosphere, such as higher seas, fiercer storms and deadlier fires. A
new flood wall is rising at the US Naval Academy in Maryland; a
low-lying Air Force runway is being elevated in Virginia; and projects
are underway to reduce wildfire risk around various military sites in
Hawaii.
Work that was
previously described as confronting the climate threat is now touted for
ensuring “resilience” and “readiness.” The semantics are a nod to
necessity: At stake are hundreds of billions of dollars of assets and
the ability to launch missions quickly and smoothly.
Much
of the military’s resilience work began years ago; construction
timelines are long. The $900 billion 2026 National Defense Authorization
Act, which Trump signed into law in December, includes measures that
could be said to come under the umbrella of climate adaptation. The law
bolsters the military’s ability to respond to wildfires; raises the cost
limit for replacing structures destroyed by disasters; and requires
military leaders to identify the biggest risks to water security on
bases.
Close to $400
billion of federal government assets, most of them belonging to the
Defense Department, are at high risk of being hit by a major coastal
flood or storm in coming years, according to a Bloomberg Law analysis.
The
Pentagon explicitly recognized the warming climate as a danger for many
years. The 2008 National Defense Strategy flagged climate change as an
emerging risk, and two years later it was named a national security
threat in the Pentagon’s Quadrennial Defense Review. After that, the
Defense Department and the individual armed forces put out
a stream of climate and sustainability plans. (Some have now been
removed from government websites.)
James
Mattis, who served as defense secretary during President Donald Trump’s
first term, described climate change as a destabilizing force in 2017.
His Biden-era successor Lloyd Austin said in 2021, “We face all kinds of
threats in our line of work, but few of them truly deserve to be called
existential. The climate crisis does.”
Trump
and Hegseth have made a sharp pivot. In a March 2025 memo to military
leaders, Hegseth called climate change a “distraction” from fighting
wars, ordered that references to it be removed from mission statements
and barred any environmental initiatives from being included in the
Future Years Defense Program, a strategic plan.
Hegseth
also included a caveat big enough to steer an aircraft carrier through.
“Nothing in this memorandum,” he wrote, “shall be construed to prevent
the department from assessing weather-related impacts on operations,
mitigating weather-related risks, conducting environmental assessments,
as appropriate, and improving the resilience of military installations.”
The
overarching goal at Tyndall, Bartlow said, is “preserving lethality in a
high-end combat capability. When we talk about resilience, it’s focused
on preserving that combat capability.” If another Category 5 hurricane
hits, “there’ll be some interruptions, but the idea is you’ll be able to
recover this installation quickly,” hesaid. “You can make that direct
link back to readiness.”
The
Atlantic meridional overturning circulation is a major part of global
climate system and is known to be at its weakest for 1,600 years as a
result of climate crisis. Photograph: Henrik Egede-Lassen/Zoomedia/PA
The critical Atlantic current system appears
significantly more likely to collapse than previously thought after new
research found that climate models predicting the biggest slowdown are
the most realistic. Scientists called the new finding “very concerning”
as a collapse would have catastrophic consequences for Europe, Africa
and the Americas.
The Atlantic meridional
overturning circulation (Amoc) is a major part of the global climate
system and was already known to be at its weakest for 1,600 years as a result of the climate crisis. Scientists spotted warning signs of a tipping point in 2021 and know that the Amoc has collapsed in the Earth’s past.
Climate
scientists use dozens of different computer models to assess the future
climate. However, for the complex Amoc system, these produce widely
varying results, ranging from some that indicate no further slowdown by
2100 to those suggesting a huge deceleration of about 65%, even when
carbon emissions from fossil fuel burning are gradually cut to net zero.
The research combined real-world ocean
observations with the models to determine the most reliable, and this
hugely reduced the spread of uncertainty. They found an estimated
slowdown of 42% to 58% in 2100, a level almost certain to end in
collapse.
The Amoc is a major part of the
global climate system and brings sun-warmed tropical water to Europe and
the Arctic, where it cools and sinks to form a deep return current. A
collapse would shift the tropical rainfall belt on which many millions
of people rely to grow their food, plunge western Europe into extreme
cold winters and summer droughts, and add 50-100cm to already rising sea
levels around the Atlantic.
Dr Valentin
Portmann, at the Inria Centre de recherche Bordeaux Sud-Ouest in France
and who led the new research, said: “We found that the Amoc is going to
decline more than expected compared to the average of all climate
models. This means we have an Amoc that is closer to a tipping point.”
Prof
Stefan Rahmstorf, at the Potsdam Institute for Climate Impact Research
in Germany, said: “This is an important and very concerning result. It
shows that the ‘pessimistic’ models, which show a strong weakening of
the Amoc by 2100, are, unfortunately, the realistic ones, in that they
agree better with observational data.”
He
added: “I now am increasingly worried that we may well pass that Amoc
shutdown tipping point, where it becomes inevitable, in the middle of
this century, which is quite close.”
Rahmstorf, who has studied the Amoc for 35 years, has said a collapse must be avoided “at all costs”.
“I argued this when we thought the chance of an Amoc shutdown was maybe
5%, and even then we were saying that risk is too high, given the
massive impacts. Now it looks like it’s more than 50%. The most dramatic
and drastic climate changes we see in the last 100,000 years of Earth
history have been when the Amoc switched to a different state.”
The Amoc is slowing because air temperatures are
rising rapidly in the Arctic because of global heating. That means the
ocean cools more slowly there. Warmer water is less dense and therefore
sinks into the depths more slowly. This slowing allows more rainfall to
accumulate in the salty surface waters, also making it less dense, and
further slowing the sinking and forming an Amoc feedback loop.
The
Amoc system is highly complex and subject to random natural variations,
making precise predictions impossible. However, a major weakening is
now expected by scientists and that alone could have serious impacts in
the decades to come.
The new research, published in the journal Science Advances,
explored four different ways of using real-world observations to assess
the models. They found a method called ridge regression, which had been
little used in climate science before now, provided the best results.
The
Amoc is difficult to model because it is governed by subtle differences
in water density caused by salinity changes over the entire Atlantic.
The reduction in uncertainty in the new analysis results from
identifying the models that better reflect surface salinity in the south
Atlantic, which scientists already knew was important. This makes the
work “very credible”, said Rahmstorf.
Rahmstorf
said Amoc slowdown in 2100 may be even greater than in the new,
pessimistic assessment. This is because the computer models do not
include the meltwater from the Greenland ice cap that is also freshening the ocean waters: “That is one additional factor that means the reality is probably still worse.”
A person wears a hat while walking along the Strand in Redondo Beach, California, on 20 March 2026, during a heatwave. Photograph: Patrick T Fallon/AFP/Getty Images
Associated Press
March’s persistent unseasonable heat was so intense
that the continental United States registered its most abnormally hot
month in 132 years of records, according to federal weather data. And
the next year or so looks to turn the dial up on global warmth even
more, as some forecasts predict a brewing El Niño will reach super strength.
Not
only was it the hottest March on record for the US but the amount it
was above normal beat any other month in history for the lower 48
states. March’s average temperature of 50.85F(10.47C) was 9.35F (5.19C)
above the 20th-century normal for March.
That
easily passed the old record of 8.9F set in March 2012 as the most
abnormally hot month on record – regardless of the month of the year –
according to records released on Wednesday by the National Oceanic and
Atmospheric Administration (Noaa).
The average maximum temperature for March was
especially high at 11.4F above the 20th-century average and was almost a
degree warmer than the average daytime high for April, Noaa said.
Six
of the nation’s top 10 most abnormally hot months have been in the last
10 years. This February, which was 6.57F above 20th-century normal, was
the 10th highest above normal.
“What we
experienced in March across the United States was unprecedented,” said
Shel Winkley, a meteorologist with Climate Central, a non-profit science
research group.
“One reason that’s so
concerning is just the sheer volume of records, all-time records that
were set and broken during that time period,” Winkley said. “But also
this is coming on the heels of what was the worst snow year. And the
hottest winter of record.”
April 2025 to March 2026 was the warmest 12-month period on record in the continental United States, according to Noaa.
On
20 and 21 March, about one-third of the nation felt unseasonable heat
that would have been virtually impossible without human-caused climate
change, Climate Central calculated.
More
than 19,800 daily temperature records were broken for heat across the
country, according to meteorologist Guy Walton, who analyzes Noaa data.
More than 2,000 places set monthly records for heat – harder to break
than daily records – Walton calculated. That’s more March heat records
set just last month than in entire decades in the past.
All those broken records “tells us that climate change is kicking our butts”, said Jeff Masters, a Yale Climate Connections meteorologist.
“January
through March period was the driest on record for the contiguous US. So
not only was it hot, it was record dry as well,” Masters said. “And
that’s a bad combination for water availability, for agriculture, for
river levels, for navigation.”
The European
climate and weather service Copernicus and Noaa are both forecasting a
“super” strong El Niño to form in a few months and intensify into the
winter.
“A strong El Niño could plausibly push
global temperatures to new record levels in late 2026 and into 2027,”
Victor Gensini, a Northern Illinois University meteorology professor,
said.
Right now, the Arctic is maxing out on sea ice – the cold of
winter has built up over months of darkness, and ice has spread as far
south as it will all year. It’s the North Pole’s sea ice maximum, except
this year, it’s alarmingly low.
There is roughly half a million square miles of ice missing
in this year’s “max,” compared to average — an amount twice the size of
Texas.
It’s the latest profoundly worrying signal from the top of
the planet, a region which has become a clear victim of the climate
crisis as humans burn fossil fuels, and increasingly a geopolitical hotspot as melting ice opens up commercial and military opportunities.
Winter is when Arctic ice builds up, typically reaching its
maximum extent in March. This year, when scientists from NASA and the
National Snow and Ice Data Center measured it on March 15, they found
the ice had reached 5.52 million square miles — roughly 9% lower than
the average between 1981 and 2010.
It came in just below last year’s record maximum of 5.53
million square miles, but close enough to it that it’s technically a
tie, and is the lowest peak observed since satellite records began in
1979.
“A low year or two don’t necessarily mean much by
themselves,” said Walt Meier, a NSIDC ice scientist, but when looked at
in the context of a multi-decade downward trajectory, “it reinforces the
dramatic change to Arctic sea ice throughout all seasons.”
The Arctic will be ice-free in the summer at some point by
2050, even if humans stop pumping out climate pollution, according to a
2023 study.
Disappearing sea ice has global impacts. Ice acts like a
giant mirror, reflecting the sunlight away from the Earth and back into
space. As it shrinks, more of the sun’s energy is absorbed by the dark
ocean, which accelerates global heating.
This new record is not a surprise as Arctic sea ice had been
running at near record lows all winter, said Jennifer Francis, a senior
scientist at Woodwell Climate Research Center. But it’s one more alarm
bell.
“Like when a person’s blood pressure is out of whack
signaling a health problem, the ongoing loss of sea ice is yet another
symptom indicating the Earth’s climate is in big trouble,” she said.
The cause is no mystery she added, “the ongoing buildup of
heat-trapping gases in the atmosphere from burning fossil fuels is
warming the oceans, heating the air, melting the ice, and worsening
weather extremes all around the world.”
The waters of
southern California historically warm every few years. But the marine
heatwave that started last fall wasn’t caused by tropical currents. Photograph: Kevin Carter/Getty Images
Researchers warn the high-pressure conditions could disrupt marine life and ecosystems if it continues
For more than a century, shoreline stations operated by the Scripps Institution of Oceanography have measured water temperatures along the California coast. This year, they are flashing a warning sign.
Over the last three months, several stations have repeatedly posted record-breaking daily high temperatures – with the La Jolla station registering temperatures a full 10F above historical average at one point last month.
The
waters of southern California historically warm every few years as
tropical currents make their way north, a phenomenon known as El Niño.
But the marine heatwave
that started last fall wasn’t caused by tropical currents. Instead, a
high-pressure atmospheric system – think of calm, sunny days – has
perched above southern California, warming both air and sea above
historic levels. The same phenomenon has helped fuel a ferocious
California heatwave on land.
The extended ocean warming has drawn comparisons
to “the Blob”, a three-year marine heatwave caused by similar prolonged
high-pressure conditions a decade ago that devastated marine life.
The next few weeks are likely to determine whether this marine heatwave
fizzles out or evolves into something more Blob-like, scientists say.
“The
biggest concern is how the year plays out,” Andrew Leising, an
oceanographer with the National Oceanic and Atmospheric Administration,
said. “We could be looking at much larger impacts next fall and winter,
if it stays warm and then it’s followed by a strong El Niño.”
It’s typical in the spring for shifting
atmospheric conditions to generate north-westerly winds that push warm
surface water back out to the open ocean, allowing cooler water from
below to rise to the surface – a phenomenon called upwelling. Upwelling
brings nutrient-rich water from the depths to the surface, feeding the
phytoplankton that play a crucial role in supporting much of
California’s marine life.
Over the last few
days, high water temperatures have cooled somewhat, raising the prospect
that the heatwave may be dissipating already. It will take more time,
however, to know for sure that the heat is clearing.
“The
expectation right now is that likely the waters down to even southern
California should start cooling a little bit into next month, but it’s
not a guaranteed thing,” Leising said. “The concern is the sequence of
events and how they unfold.”
Prolonged ocean
heat has a devastating impact on phytoplankton and can cause harmful
algal blooms. Those changes can wreak havoc on many forms of marine
life, from sea lions and dolphins, to shore birds and halibut.
The Blob years led to one of the worst Dungeness crab seasons in recent
history, said Melissa Carter, a researcher at the UC-San Diego Scripps
Institution of Oceanography.
Such
heatwaves are becoming more common and lasting longer, partly because
of the slow warming of the oceans driven by the climate crisis, and
partly because of atmospheric changes that scientists are still
struggling to understand.
“The question is
what’s causing us to have these extreme warm temperatures?” Carter said.
“What are the drivers? That’s what we’re trying to find out.”
What concerns Carter is that once these
high-pressure systems establish themselves in an area, they create a
“feedback loop” that tends to reinforce warm, calm conditions, making
upwelling less likely to occur, she said.
“If
these systems do become that strong and persistent, where they come
every year, it can have the potential to shut down upwelling,” Carter
said. “Everything we think of related to the health of the ecosystems of
the west coast could be forever altered.”
The
lingering ocean heat offers a few upsides, though they pale in
comparison with the costs. The warmer water temperatures bring tuna far
closer to shore, making it easier to fish for them. Surfers and swimmers
have also enjoyed warmer water through the winter.
“I
enjoy being in the water when it’s a marine heatwave,” Carter said.
“But our ocean should not be a swimming pool. Nothing can live in a
swimming pool. That’s not what we want.”
Snow surveys taking place across the American
west this week are offering a grim prognosis, after a historically warm
winter and searing March temperatures left the critical snowpack at
record-low levels across the region.
Experts
warned that even as the heat begins to subside, the stunning pace of
melt-off over the past month has left key basins in uncharted territory
for the dry seasons ahead. Though there’s still potential for more snow
in the forecast, experts said it will likely be too little too late.
“This
year is on a whole other level,” said Colorado State University
climatologist Dr Russ Schumacher, speaking about the intense heat that
began rapidly melting the already sparse snowpack in March. “Seeing this
year so far below any of the other years we have data for is very
concerning.”
Acting as a water savings account of sorts,
snowpacks are essential to water supply. Measurements taken across the
west during the week of 1 April are viewed as important indicators of
the peak amounts of water that might melt into reservoirs, rivers and
streams, and across thirsty landscapes through the summer.
It’s
not just the amount of snow left on mountaintops that’s concerning
experts, but the amount of moisture still frozen within them. “Snow
water equivalent” (SWE), a measurement of what could melt off to supply
natural and manmade systems, is exceptionally low.
Snowpack in California’s Sierra Nevada. Source: Nasa.
California’s Sierra Nevada had just 4.9in of SWE, or 18% of average, as of Monday, ahead of the state’s official 1 April survey,according
to the state’s department of water resources. In the Colorado River
headwaters, an important basin that supplies more than 40 million people
across several states, along with 5.5 million acres of agriculture, 30
tribal nations, and parts of Mexico, had just over 4in of SWE on Monday,
or 24% of average.That’s less than half what was previously considered the record low.
Schumacher
said the incoming storm could slow the early melting but won’t be
enough to pull the basins back from the brink. Snow water equivalent
measurements going into April were at levels typically seen in May or
June, after months of melt-off, according to Schumacher.
The issue is extremely widespread.
Data from a branch of the US Department of Agriculture (USDA), which
logs averages based on levels between 1991 and 2020, shows states across
the southwest and intermountain west with eye-popping lows. The Great
Basin had only 16% of average on Monday and the lower Colorado region,
which includes most of Arizona and parts of Nevada, was at 10%. The Rio
Grande, which covers parts of New Mexico, Texas, and Colorado, was at
8%.
“This year has the potential of being way worse than any of the years we have analogues for in the past,” Schumacher said.
The snowpack in the Colorado Rocky Mountains. Source: Nasa.
‘Nothing short of shocking’
Even with near-normal precipitation across most of the west, every major river basin across the region was grappling with snow drought when March began,
according to federal analysts. Roughly 91% of stations reported
below-median snow water equivalent, according to the last federal snow
drought update compiled on 8 March. Water managers and climate experts
had been hopeful for a March miracle – a strong cold storm that could
set the region on the right track. Instead, a blistering heatwave unlike
any recorded for this time of year baked the region and spurred a rapid
melt-off.
“March is often a big month for
snowstorms,” Schumacher said. “Instead of getting snow we would normally
expect we got this unprecedented, way-off-the-scale warmth.”
More than 1,500 monthly high temperature records were broken
in March and hundreds more tied. The event was “likely among the most
statistically anomalous extreme heat events ever observed in the
American south-west”, climate scientist Daniel Swain said in an analysis posted this week.
“Beyond
the conspicuous ‘weirdness’ of it all,” Swain added, “the most
consequential impact of our record-shattering March heat will likely be
the decimation of the water year 2025-26 snowpack across nearly all of
the American west.”
Calling the toll left by the heat “nothing short of shocking”, Swain noted that California
is tied for its worst mountain snowpack value on record. While the
highest elevations are still coated in white, “lower slopes are now
completely bare nearly statewide”.
The snow is
melting so fast in the Sierra that, if it continues at its current
rate, little would be left by early April. It’s unlikely to keep up this
astounding pace, but there’s still high potential for the earliest
melt-off on record in the state, according to Swain.
“It
is increasingly likely this season will be the one of the lowest 1
April snowpacks on record and one of the earliest peak snowpacks in the
21st century,” said Andy Reising, manager of California DWR’s Snow
Surveys and Water Supply Forecasting Unit. “This year has featured many
of the factors California is expected to see more of in the future:
winters with more rain and less snow and stretches of hot and dry
conditions.”
Snow around the Great Salt Lake seen between February versus March. Source: Nasa.
California’s reservoirs are nearly all filled beyond their historic averages,
however, thanks to a series of robust rains. While this will help
support water supplies, it will also mean fast-melting snow may be
harder to capture.
In the Colorado River
Basin, the situation could be even more dire. The two largest reservoirs
on the Colorado River are Lake Mead and Lake Powell, which together
account for about 90% of storage, are 25% and 33% full accordingly, as of 29 March, and there is little to fill them.
Already
officials are in the process of relocating a floating marina on Lake
Powell in anticipation of the quickly receding water levels, as experts
warn the vital reservoir could drop to the lowest levels recorded since
it was filled in the 1960s. If they fall far enough, the system would
cease to function altogether. So-called “deadpool” – when water isn’t
high enough to pass through the dams, generate hydroelectric power, and
be distributed downriver – would be catastrophic.
The Colorado River has been overdrawn for more
than a century but rising temperatures and lower precipitation are
putting more pressure on the system that depended on by cities, farms,
industries, and wildlife across the west. The extreme conditions have
added more urgency and greater tensions to fraught negotiations
over who will bear the brunt of badly needed cuts. Seven states that
have blown past two key deadlines are still locked in a stalemate over
how the river’s essential resources will be managed through a hotter and
drier future.
But the dire snowpack numbers
have pushed some municipalities to initiate early water restrictions.
Local officials in Salt Lake City, Utah,
have called on residents and businesses to begin conserving, with a
goal to cut up to 10 million gallons, while city facilities will curb
10% of their use. Across Colorado, there are local orders that limit
lawn watering, and in Wyoming residents were warned that full
restrictions on outdoor irrigation could come as early as May. Farmers
and ranchers across the west are also having to make hard decisions and
big adjustments with smaller allocations of water and a recognition that
supplies will be strained.
A troubling outlook for fire season
The
fast-melting snow is expected to have profound impacts on drinking
water supply, agriculture production, and outdoor recreation. It could
also set the stage for bigger blazes.
“Unless
there’s a major change in the weather patterns and we somehow pull out
some sort of miracle springtime precipitation, we’re looking at an
extended fire season,” said Dr Joel Lisonbee, senior associate scientist
at the Cooperative Institute for Research at the University of Colorado
Boulder, noting that there’s not a one-to-one relationship between
snowpack and fire, but they are connected.
“In
any sort of fire situation, you need some spark or ignition,” he said.
Landscapes that would typically spend longer underneath a protective
blanket of snow will become more primed to burn. Fire season may “begin
weeks to months earlier than what we would usually expect,” he said.
“These high temperatures and low snowpack will lead to a rapid drying of
the vegetation that’s around, and that will lead to this early start.”
Dozens
of large destructive fires have already erupted in recent weeks across
the Intermountain West and the High Plains, spurred by extreme heat and
low moisture. More than 1.5m acres have already burned this year across
the US, more than double the 10-year average.
While
Schumacher said he expects this year to be a standout one, the climate
crisis is fueling warming trends that climate scientists have long
warned will leave the west hotter and drier. Seasons with snow in the US
west are shrinking while high fire risks stretch across more months.
“Climate
change is going to result in a lot of these extreme events worsening,”
said Dr Abby Frazier, a climatologist and assistant professor at Clark
University, who added that compound events, where hazards overlap or
occur in quick succession, are on the rise. The heat and the drought
this year, served as a one-two punch, and will work together to produce
greater dangers from fire.
She emphasized the
need to take transformative action, and prioritize adaptation and
mitigation. “It is heartbreaking to see it all playing out as we have
predicted for so long,” she said. “The changes we have teed up for
ourselves are going to be catastrophic.”
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