15,000 scientists give catastrophic warning about the fate of the world in new ‘letter to humanity’

A new, dire "warning to humanity" about the dangers to all of us has been written by 15,000 scientists from around the world.

The message updates an original warning sent from the Union of Concerned Scientists that was backed by 1,700 signatures 25 years ago. But the experts say the picture is far, far worse than it was in 1992, and that almost all of the problems identified then have simply been exacerbated.

Mankind is still facing the existential threat of runaway consumption of limited resources by a rapidly growing population, they warn. And "scientists, media influencers and lay citizens" aren't doing enough to fight against it, according to the letter.

If the world doesn't act soon, there be catastrophic biodiversity loss and untold amounts of human misery, they warn.

Only the hole in the ozone layer has improved since the first letter was written, and the letter urges humanity to use that as an example of what can happen when it acts decisively. But every single other threat has just got worse, they write, and there is not long left before those changes can never be reversed.

There are some causes for hope, the letter suggests. But humanity isn't doing nearly enough to make the most of them and soon won't be able to reverse its fate.

"Soon it will be too late to shift course away from our failing trajectory, and time is running out," the letter warns. "We must recognize, in our day-to-day lives and in our governing institutions, that Earth with all its life is our only home."

10 photographs to show to anyone who doesn't believe in climate change

10 show all 10 photographs to show to anyone who doesn't believe in climate change

1/10 A group of emperor penguins face a crack in the sea ice, near McMurdo Station, Antarctica Kira Morris

2/10 Amid a flood in Islampur, Jamalpur, Bangladesh, a woman on a raft searches for somewhere dry to take shelter. Bangladesh is one of the most vulnerable places in the world to sea level rise, which is expected to make tens of millions of people homeless by 2050. Probal Rashid

3/10 Hanna Petursdottir examines a cave inside the Svinafellsjokull glacier in Iceland, which she said had been growing rapidly. Since 2000, the size of glaciers on Iceland has reduced by 12 per cent. Tom Schifanella

4/10 Floods destroyed eight bridges and ruined crops such as wheat, maize and peas in the Karimabad valley in northern Pakistan, a mountainous region with many glaciers. In many parts of the world, glaciers have been in retreat, creating dangerously large lakes that can cause devastating flooding when the banks break. Climate change can also increase rainfall in some areas, while bringing drought to others. Hira Ali

5/10 Smoke – filled with the carbon that is driving climate change – drifts across a field in Colombia. Sandra Rondon

6/10 A river once flowed along the depression in the dry earth of this part of Bangladesh, but it has disappeared amid rising temperatures. Abrar Hossain

7/10 Sindh province in Pakistan has experienced a grim mix of two consequences of climate change. “Because of climate change either we have floods or not enough water to irrigate our crop and feed our animals,” says the photographer. “Picture clearly indicates that the extreme drought makes wide cracks in clay. Crops are very difficult to grow.” Rizwan Dharejo

8/10 A shepherd moves his herd as he looks for green pasture near the village of Sirohi in Rajasthan, northern India. The region has been badly affected by heatwaves and drought, making local people nervous about further predicted increases in temperature. Riddhima Singh Bhati

9/10 A factory in China is shrouded by a haze of air pollution. The World Health Organisation has warned such pollution, much of which is from the fossil fuels that cause climate change, is a “public health emergency”. Leung Ka Wa

10/10 Water levels in reservoirs, like this one in Gers, France, have been getting perilously low in areas across the world affected by drought, forcing authorities to introduce water restrictions. Mahtuf Ikhsan

A host of environmental calamities are highlighted in the warning notice, including catastrophic climate change, deforestation, mass species extinction, ocean "dead zones", and lack of access to fresh water.

Writing in the online international journal BioScience, the scientists led by top US ecologist Professor William Ripple, from Oregon State University, said: "Humanity is now being given a second notice ... We are jeopardising our future by not reining in our intense but geographically and demographically uneven material consumption and by not perceiving continued rapid population growth as a primary driver behind many ecological and even societal threats.

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"By failing to adequately limit population growth, reassess the role of an economy rooted in growth, reduce greenhouse gases, incentivise renewable energy, protect habitat, restore ecosystems, curb pollution, halt defaunation, and constrain invasive alien species, humanity is not taking the urgent steps needed to safeguard our imperilled biosphere."

In their original warning, scientists including most of the world's Nobel Laureates argued that human impacts on the natural world were likely to lead to "vast human misery".

The new notice, written as an open-letter "viewpoint" article, won the support of 15,364 scientists from 184 countries who agreed to offer their names as signatories.

The authors drew on data from government agencies, non-profit organisations and individual researchers to set out their case that environmental impacts were likely to inflict "substantial and irreversible harm" to the Earth.

Prof Ripple said: "Those who signed this second warning aren't just raising a false alarm. They are acknowledging the obvious signs that we are heading down an unsustainable path.

"We are hoping that our paper will ignite a widespread public debate about the global environment and climate."

Progress had been made in some areas - such as cutting ozone-depleting chemicals, and increasing energy generated from renewable sources - but this was far outweighed by the damaging trends, said the scientists.

They pointed out that in the past 25 years:

The amount of fresh water available per head of population worldwide has reduced by 26%.

The number of ocean "dead zones" - places where little can live because of pollution and oxygen starvation - has increased by 75%.

Nearly 300 million acres of forest have been lost, mostly to make way for agricultural land.

Global carbon emissions and average temperatures have shown continued significant increases.

Human population has risen by 35%.

Collectively the number of mammals, reptiles, amphibians, birds and fish in the world has fallen by 29%.

Prof Ripple and his colleagues have formed a new independent organisation called the Alliance of World Scientists to voice concerns about environmental sustainability and the fate of humanity.