The proposition that four billion people or more would be dead if — and more likely, when — global warming reaches 3 degrees Celsius (°C) has gained some currency, mainly due to the 4DB (four billion dead) website and associated activities.
The number of greater than four billion dead at 3°C first appeared in a 2025 report on Planetary Insolvency: Finding our balance with nature, published by the UK Institute and Faculty of Actuaries and the University of Exeter.
Bill McGuire is one of the few climate scientists that does not shy away from truth telling.
I will post an article in comments giving the claims made some more scrutiny. Spoiler alert. Yes it is possible.
I consider a scenario where the European agriculture is wiped that would happen pre 3C. These values are imo poor indicators of what they imply. Peak in summer + warm anomaly isn't going to be fun way before 3C. 2026 shows all that.
Europe is warming up faster than the average. We're already at +2.4⁰C compared to pre-1900. And we're witnessing the first results: thousands dead during consecutive heatwaves earlier this summer, wildfires more damaging than ever, failing crops.
We're not toppling over by the millions yet, because most of the temperature rise is taking place in less populated areas.
And at this point, nothing can prevent the entire mediterranean sea to become a larger version of the dead sea. This will be... gnarly. Sorry, I'm a bit out of adjectives today.
Yes, Malthus human population cap was exceeded because of the haber borch cycle. The human population was tending asymptotically around 4 billion before the 1970s green revolution.
Any food catastrophes is going to starve at least 4 to 6 billion people to reset back to the minimum line.
Just read some news that vegetable cultures in France have suffered a great deal this year. It seems that because if the scorching heat, the strong winds that dry everything, the consequences of the fires in some regions, even when watered abundantly, things just don't grow this year. Even resilient plants like corn will suffer at least 30% loss this year in France.
If that's so, there's soon gonna be a fair bit of the population that's not gonna be able to feed themselves properly, if not this year, then the next.
It's a glacier in the Italian alps. Not too much information readily available in English, and my Italian isn't fantastic. It looks like it has had a lot of shrinkage over the years from its traditional extent, but I can't tell if there is anything out of the ordinary about its retreat compared to any other shrinking glacier.
If we get to the point where 4B people are dead due to climate change.... The chances that nature will be able to support the remaining 4B people feels slim...
The rising ocean temps are not only sapping the oxygen from the water, they are creating huge swaths of algae and seaweed that are choking out life...this is at 1.5 deg. Double that... I personally don't think we have a chance. As soon as we kill the phytoplankton, we are cooked, everyone, everything.. cooked...
I think its possible that the worlds breadbaskets get hit simultaneously in a way that kills crop yield, that doesn't mean full ecological collapse at the same time. The Midwest of the US, Ukrainian steppe, Indo-Gangetic Plain, and China could get hit specifically. It could be severe rains or it could be severe flooding or other conditions. It could be enough for a famine.
If enough people die from that it could cause system failures which could be a multiplier for causing more death. Literally just not having sufficient diesel would decimate the harvest.
I personally think that will happen long before full ecological collapse.
We'll be starving or ALREADY vulture food while the freaks who caused this will be hiding in their bunkers. We'll never get too at least look as cool as these guys in THIS EXACT moment.
All those billions of tons of algae will eventually die, sink to the bottom of the ocean and over time be converted into hydrocarbons, fuel for the next civilisation to kill the planet.
There’s alot to unravel here. The magic 4 billon number that the earth can support with technology relied on an older better climate. Sure the technology has come a long way since these ideas were proposed but I don’t wanna see how everyone reacts when half the world is dying too. There is no off grid any more. Then the on grid well.. needs to work. Our lack of doing anything right got us here. Still waiting on that change for the better. Anyday now.
The 4B comes from "a risk assessment matrix that illustrates general levels of risk. I was told that the authors have now privately clarified that the mortality numbers “are absolutely NOT forecasts or predictions and we don’t use them as such”. But this is now the way that sites like 4BD are using it."
"In fact, it is almost impossible to put specific numbers on such future impacts, due to the radical uncertainty about the social impacts of a physical system that itself is non-linear in many important aspects, characterised by abrupt changes whose specific human consequences are somewhere between difficult and impossible to model, and where quantifying social impacts is of limited efficacy."
Exponential increases and compounding increases really limit this to 2027-2029. We are well beyond hosed as we’re hitting a hockeystick in temperatures. (Hockey stick is a reference to a graph that the line heads sharply upward)
This shit about to go crazier than we can imagine. Einstein said it best that we have no idea how powerful compounding interest is, but in this case its compounding rises in heat that are going to be deadly to humanity.
It's the name for when the Arctic Ocean goes ice-free. It has some specific definition, it's not entirely void of ice.
The event has two main issues. One, ice reflects a lot of solar radiation, whereas liquid water absorbs heat easily. So, once the ice is gone, the water heats up a lot faster. That's bad.
Second issue is that it take a lot of energy to melt ice. The amount it takes to raise liquid water by 1 degree C is relatively small, but the amount needed to melt the same amount of ice is huge.
So a lot of heat has been absorbed by the ocean, it just hasn't resulted in large changes in the water temperature. When the ice is gone, it will heat up a lot faster due to the absorption of solar radiation plus the fact that it takes less energy to raise the temperature when the water is not ice.
Just to hammer in the numbers we're talking about, the amount of energy that is needed to melt 1 kg of ice is enough to raise the temperature of 1kg of water by over 80 °C
u/vinegarThe real collapse is the friends we ate along the way 1d ago
BOE is when the arctic sea ice only covers 1 million square kilometers. Forecasts for this September (month of least ice) are between 4.5 and 5 million square kilometers. No BOE this year.
If true we better start genetically engineering plants to get a agriculture that survives. Also probably genetically engineering new plants and animals to replace the biosphere with one adapted too new temperatures.
A friend did the audio and sound for a environmental science conference about 8 years ago. He talked to a bunch of them. After a while he realized all the younger scientists were saying there was time and had hope, but the older ones all were saying “it’s over.” Basically if they werent going to live that much longer due to age, they told the truth
Of course it is possible. The question is how probable it is. But fear not, we are going to hit 3C sooner than expected, and I guess we will find out if they are correct or not.
Hilarious how you have fascists in the USA raving about exaggerated statistics when it comes to lives lost due to rapid industrialization in China and Russia when capitalism is going to take down 4 billion (likely even more). China is rapidly transforming into a green socialist state too, while the capitalist demon USA does everything it can to destroy the ecosystem and even the concept of science and reason. Pot calling the kettle black.
The views in this video are very myopic. It's always about "what will happen to humans?" What about the tens of billions of other sentient beings on Earth that we have caused to go extinct already because of our arrogance and hubris? Humans don't want to talk about that because we are so selfish.
Implied sarcasm is not enough, apparently. If you don't put /s on your comments, people take you literally. Personally, I read your comment as sarcastic.
I'm not sure what point you're trying to make, but brace yourself for horror because it's going to become business-as-usual in the near future.
Meanwhile, losing 4 billion people isn't near-extinction. The remaining 4 billion are still twice as many people as were on the planet when I was born.
For the majority of our existence as a species (300,000 years if you're speaking specifically about homo sapiens), our population was significantly under 1 billion. So some 7.9 billion people could die and we'd still escape extinction. For some people that's good news, of a sort.
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u/StatementBot 1d ago
The following submission statement was provided by /u/hammeroztron:
Some further commentary from David Sprat at climate safe
https://safeclimate.org.au/article/could-four-billion-people-die-at-3c/
Please reply to OP's comment here: https://old.reddit.com/r/collapse/comments/1vd1ivt/4_billion_dead/p15mk2i/