Orange rivers, longer days: Nine ways our planet changed in its hottest year yet

The Santa Ana winds started to stir over the desert inland from Los Angeles on January 2 and within days they were driving a firestorm through the city.

Another year had begun with our news dominated by a disaster accelerated by climate change.

Last year was the hottest in history, with global temperatures on average 1.55 degrees higher than the pre-industrial period. The figures, confirmed by the World Meteorological Organisation earlier this month, eclipsed the previous hottest year – 2023. The 10 hottest years in recorded history are the past 10 years.

“This is climate breakdown – in real-time,” United Nations Secretary General António Guterres said in his New Year’s Eve address. “We must exit this road to ruin, and we have no time to lose.”

Weeks later, newly installed US President Donald Trump pulled the United States out of the Paris climate agreement, joining company with Libya, Yemen and Iran.

As the effects of climate change intensified last year, some impacts on humanity were immediate and brutal – an estimated 8700 people were killed, and 40 million people displaced in floods, droughts, tropical cyclones and landslides over the past year.

Others are yet to make their implications known.

Below is a glimpse of the changes our country and world experienced as we sweltered through our hottest year.

1. Rain where once there was ice

A heatwave hit Antarctica in July, pushing land temperatures to more than 28 degrees above average over much of the east of the world’s coldest and driest continent.

The temperatures stayed inexplicably high for 10 days, driven in part by a previous record-breaking heatwave that two years earlier had depleted the region’s sea ice.

Scientists collecting moss samples in Antarctica in February last year.Credit: Laura Phillips

With warm temperatures came rain, a phenomenon normally alien to Antarctica, killing mosses and lichens that have thrived close to Australian bases in the east.

Hit by pulses of warm weather and rains, the plants froze and thawed, damaging their vascular structures and inhibiting their photosynthetic activity, explains Dr Justine Shaw from Securing Antarctica’s Future at Queensland University of Technology.

The rain also seeped into the downy immature feathers of emperor penguin chicks and froze when temperatures dropped, a phenomenon described by Shaw as “just another stress, another pressure from climate change” with unclear consequences.

In a previous heatwave in 2022, a report published in August revealed, not a single chick survived the breeding season in four of five colonies under observation in the Bellingshausen Sea because the ice beneath them broke up before they were mature enough to survive the sea.

2. Toxic orange rivers

At the opposite end of the Earth, Arctic streams are turning bright orange as permafrost melts and leaches iron and toxic metals into the water.

Orange streams are increasingly common in northern Alaska.Credit: Josh Koch/US Geological Survey

The damaged streams span 1000 kilometres of land, including the traditional territory of native Alaskans and the watersheds of several significant rivers, and could affect the quality of drinking water and subsistence fishing.

Previous studies have focused on the gradual shifts over decades in the chemistry of Arctic rivers. This study, published in Nature in 2024, looked at 75 visibly impaired streams – tributaries of 41 river catchments – and demonstrated the damage had mainly occurred in the past decade.

Nearly all were in remote areas, tens to hundreds of kilometres from land-use impacts such as mining or roads.

The scientists published evidence it was the result of melting permafrost because the perennially frozen Arctic soils contain large amounts of organic carbon, nutrients, mercury and other metals. This turns the streams acidic and makes them more turbid, correlated with declines in macroinvertebrate diversity and fish abundance.

3. Longer days, more earthquakes

That melting ice also exerted a planet-spanning, or planet-spinning influence: 2024 was the year we learnt climate change is warping time.

As ice melts, the extra water flows towards the equator, meaning mass from the poles redistributes to Earth’s mid-section. That water bulging at the equator is slowing our planet’s spin, like a dancer slowing a pirouette by spreading her arms. As a result, our days are growing longer.

The lengthening is only about 1.33 milliseconds per 100 years, but that’s the fastest rate of rotational deceleration measured in at least a century.

In our era of smartphones, satellites and driverless cars, the worldwide co-ordination of timekeeping is essential. As the researchers wrote in their Nature paper, those milliseconds pose an “unprecedented problem for computer network timing”.

And as the Earth’s rotation slows, its crust could grow more agitated with tectonic activity – yet another weird consequence of ice melt. Analysis of Sangre de Cristo Mountains in Colorado suggested an active fault line along its western edge may have been suppressed for thousands of years by the enormous weight of a glacier. When it melted, seismological activity increased.

Rapid retreat of mountain glaciers in Alaska, the Himalayas and the Alps could boost tectonic activity in those areas, the authors wrote in their study, which added to a small but compelling body of evidence that climate change could increase the frequency of earthquakes.

4. Desperate black cockatoos invade Perth

It is said the black bodies of Carnaby’s cockatoos once darkened the skies around Perth, so large were their flocks.

A Carnaby’s black cockatoo, a threatened species endemic to southwestern Western Australia, in Perth.Credit: Getty Images

But the decimation of their habitat through the city’s sprawl has resulted in their declaration as a threatened species.

Then came the heat. Perth’s hottest ever summer in 2023-24 was followed by a delay in the onset of winter rainfall, resulting in the unprecedented failure of the coastal plain’s banksia woodlands to set seed.

Last year’s heat and the long dry wiped out what was left of the pre-eminent food source for the region’s beloved black cockatoos, and delayed or prevented the annual breeding season.

Wildlife rehabilitation centres and Perth Zoo’s veterinary clinic were flooded with emaciated black cockatoos, sometimes multiple birds a day.

In December, the WA government announced a one-off funding injection to support veterinarians on the front line. Promises to halt suburban sprawl have one by one been walked back.

5. Earth’s water cycles upended

As global temperature records were broken, water-related disasters killed more than 8700 people, displaced 40 million, and caused economic losses exceeding $US550 billion ($883 billion), the 2024 Global Water Monitor reported.

Professor Albert van Dijk of the Australian National University’s Fenner School of Environment and Society and his colleagues reported that in 2024 about 4 billion people across 111 countries – half the world’s population − experienced their warmest year yet, with 39 countries setting new heat records.

A woman looks out from her balcony as vehicles are trapped in the street after flooding in Valencia in October.Credit: AP

“Record-high monthly rainfall totals were achieved 27 per cent more frequently in 2024 than at the start of this century, whereas daily rainfall records were achieved 52 per cent more frequently,” van Dijk says.

“Record-lows were 38 per cent more frequent, so we are seeing worse extremes on both sides. From historic droughts to catastrophic floods, these extreme events impact lives, livelihoods, and entire ecosystems.”

In March and April, flash floods turned deadly in Afghanistan and Pakistan, killing more than 1000 people and destroying a million tonnes of rice. Flash floods also killed more than 200 people in Spain in October.

Meanwhile, crippling droughts reduced maize production by more than 50 per cent in southern Africa.

6. Shortages for coffee, chocolate and more

Last year was a wild ride for crop shortages and global food prices because of climate-driven heat waves and disasters.

Global coffee bean prices have soared and Australian cafes are struggling.Credit: Justin McManus

The effect was most obvious in crops such as coffee and cocoa, which are traded as commodities on global exchanges.

The price of Arabica coffee increased throughout 2024, ending the year at $US7.57 ($12.1) a kilogram, its highest level since 1972. Robusta beans – used in instant coffee and some specialty blends – had a similar price trajectory.

Climate change is coming for our chocolate too. After decades of stability, the price of cocoa tripled in 2024 and careened between deeper peaks and troughs than seen in modern times.

What is to blame? “It was absolutely the weather,” says ANZ agribusiness economist Michael Whitehead.

He explains that coffee crops were hit by heat waves and drought in Brazil and Vietnam, which between them grow most of the world’s coffee.

Coffee plants affected by drought in Sao Paulo, Brazil in September 2024.Credit: Bloomberg

For cocoa, which is mostly grown in Ghana and the Ivory Coast, production was damaged by too much rain – which brought crop diseases – followed by hot weather.

Drought and heat waves also hit olive oil production in Mediterranean Europe, resulting in price rises and product shrinkage on the supermarket shelves as far away as Australia.

And drought in Texas brought the US beef cattle herd down to its lowest level in 60 years, which Whitehead says has driven export demand for Australian beef.

7. Heatwaves kill vast swaths of the Great Barrier Reef

A global marine heatwave that began in 2023 and stretched into 2024 caused widespread coral bleaching on the increasingly vulnerable Great Barrier Reef.

Severe mass bleaching in early 2024 was the seventh on the Great Barrier Reef since 1998, and the fifth since 2016. Scientists from the University of Sydney report this event was different because, for the first time, the severe mass bleaching hit all regions of the reef – north, central and south – at once.

Researchers spent 161 days tracking the health of 462 coral colonies from their research station at One Tree Island in the southern reef.

Coral bleaching on the northern Great Barrier Reef in September 2024.Credit: © AIMS | LTMP | Linnet Reef | 29.09.2024

Of the colonies they observed, 66 per cent were bleached by February, and 80 per cent by April. By July, 44 per cent of the bleached colonies had died, including 95 per cent of some coral genera.

“The southern Great Barrier Reef, despite its protected status, was not immune to the extreme heat stress that triggered this catastrophic bleaching event,” says Professor Maria Byrne, lead author of the study published last week.

8. Voracious sea urchins devour kelp forests

Further south, the marine heatwave meant a bumper season for longspined sea urchins. Marine ecologist Dr Scott Bennett says it was especially bad in early 2024, with results not yet in for this summer.

Bennett, at the University of Tasmania and co-founder of the Great Southern Reef Foundation, says the urchins are native to NSW, but climate change is causing a population explosion and expanding their territory further south as far as Tasmania.

A barren area created by longspined sea urchins on the edge of a kelp forest off Eden on the NSW South Coast.Credit: Great Southern Reef Foundation

The effect is devastating for the Great Southern Reef, which stretches from southern NSW around under the southern side of Australia and up the Western Australian coast and is home to vast undersea kelp forests.

The urchins devour entire forests of kelp. Yet “they don’t eat themselves out of house and home”, Bennett says, because once the big kelp is gone, they switch modes and start feeding on tiny seaweeds that regrow rapidly.

No such luck for the other animals that rely on the kelp forests, including fish and seals.

There is some hope: Bennett says the spiny sea urchins have a delicious roe and there are efforts to ramp up commercial fishing to keep the species in check.

Sea urchin used in a dish at Kisuke in Sydney.Credit: Wolter Peeters

9. Category 6? Hurricane Milton reached the limit of possible strength

In October, Hurricane Milton brushed against the upper threshold of how strong a storm can possibly get – a destructive manifestation of what the extra heat trapped within our atmospheric system can do.

Tropical storms feed on heat from water below, sucking up energy to power their destructive spiral of thunderclouds. Abnormally hot 30-degree ocean water in the Gulf of Mexico fuelled Milton’s extraordinary power.

Timelapse from space of Hurricane Milton.Credit: X/@dominickmatthew

As a result, the hurricane sustained one-minute winds of nearly 300km/h as it raged offshore near Mexico’s Yucatán Peninsula before the storm spun towards Florida.

“This is considered near the theoretical maximum velocity for tropical cyclones for our planet,” says Australian climate scientist Dr Steve Turton, from Central Queensland University.

“As we continue to trap extra heat in our climate system, due to rising greenhouse gases from human activities, will we need to reconsider the 1-5 scale used for tropical cyclones [and hurricanes and typhoons] and introduce a new category 6 scale?”

A house lies toppled off its stilts after the passage of Hurricane Milton.Credit: AP

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