Thank you for this AmA!

Money aside: how are our chances to survive rising temperatures, changing landscapes, stronger storms and flutings? Are we well enough equipped, with modern technology, to grow enough food? I think about anything, from solar powered greenhouses to stuff I don‘t know exists.

Thank you for taking our questions.

Exactly how unprecedented is our current situation compared to what you've found in the record?

Asking for your educated speculation here. Have we already hit the tipping point?

Finally, is there any indication that the tipping points are reversible? For example, if a new technology came online tomorrow that magically returned greenhouse gasses to better than pre-industrial levels, would it matter?

Thank you for your work and answers.

What are some of the biggest "canaries in the coal mine" today and in the immediate future?

Thank you!
I see you mentioned 2100 as a year of a potential turning point. Can this estimate be cut dramatically by external forces such as nuclear detonations, chemical fires (ohio train) or even a severe volcanic eruption?

How long have we got?

The present rate of CO2 increase is much larger than in past disruption events. However, the critical rate of change seen in past events is only part of the story. First. the timescale of the current situation (about a century) is much shorter than past events. Second, natural processes in the oceans tend to damp perturbations of CO2, at a roughly 10,000 year timescale. The upshot is that the critical rate of the modern event must be rescaled by a factor of about 100/10000 = 0.01 to be compared to past catastrophes. When that rescaling is done, our modern disruption event, if it continues throughout this century, looks fairly similar to the runup to extreme warming events of the past, including those associated with mass extinction. A rough estimate is that the tipping point would occur late in this century. For more detail, see our papers here and here.

But that too is only part of the story. If the tipping point is real, our own calculations suggest a roughly 10000-yr trajectory during which things become progressively worse—but only if there were no negative feedbacks beyond those we currently understand that would act to arrest the trajectory. And we would imagine that new technologies—or simply improved scientific understanding—might contribute towards goading the Earth system in the right direction.

For more AMAs on this topic, subscribe to r/IAmA_Science, and check out our other topic-specific AMA subreddits here.

Thanks for the question! Unfortunately the question of how well equipped we are to survive the coming changes is pretty complex and somewhat outside of our specific expertise (we’ve been focusing more on the changes themselves). Understanding this involves not just scientific knowledge from a range of disciplines but also knowledge from social sciences about how societies will respond, what’s possible in terms of economics and policy, and so on.

We agree with you that the food question is a really important one. We’re also not experts on agriculture, but there are some other researchers and research institutes doing great work on this. Off the top of our heads, one prominent recent study is that of Gerten et al. (2020): they argue that it should in principle be possible to transform the global food system to feed 10 billion people in away that’s relatively globally sustainable. Whether this is going to be possible in practice, of course, is another matter.

What are some ways we can encourage thriving ecosystems in the surrounding areas we live? (Individually, or community/city efforts).

EDIT: Also, have you read Greta Thunberg's new book? Thoughts on it?

Thank you for doing this. Do you think that humanity should engage in climate change mitigation and adaptation, rather than attempting to reduce carbon emissions?

To be clear, I understand the science and PPM calculations, but I don't foresee a world where all countries, particularly China, India, and Russia will promote a carbon-free or low-emission economy...and I doubt that the U.S. has the willpower to do so any time soon.

What's the next mass extinction we are probably going to face? How soon? Best way to prepare oneself for it?

Thanks for the great question! One interesting phenomenon that really matches the idea of the canary is that of “early warning signals”: basically, mathematical theory predicts that a system that’s about to cross a tipping point will start fluctuating more slowly, and this can be measured. There is a lot of work going into assessing elements of the climate system that might have tipping points, and searching for such early warning signals: one recent example is the Atlantic Meridional Overturning Circulation (AMOC; think Gulf stream). Recent work (e.g. Boers 2021) suggests that the AMOC is currently exhibiting early warning signals for collapse.

With respect to the global-scale disruption events, we could say that the canary is the historical record itself. Appropriately analyzed, the record suggests that there is a critical rate of CO2 perturbation at which mass extinction occurs, and that we are on track to cross the threshold by 2100 (see also this comment). Nevertheless, since it may take thousands of years for the ultimate consequences to play out, actions we take today to mitigate this could still have an effect.

Thanks for your question! Severe volcanic eruptions would be minor perturbations (in terms of CO2 injection) compared to the fossil-fuel burning. Chemical fires even more so, but clearly they are problems by themselves. Nuclear detonation would bring us towards an entirely new set of serious risks independent of climate change.

Thank you!

This is awesome! Thank you so kuch for doing this.

I'm someone who runs Climate Adaptation training and education for an island community. Do you have any suggestions for maintaining a hopeful tone when discussing these big life changing topics?

Thanks for your question! Whatever we do, over hundreds of millions of years there will probably be a mass extinction at some point, most simply because there have been 5 mass extinctions in the last 500 million years. That said, there appears to be an unprecedented rate of species loss today, and many would argue that we are already in the sixth mass extinction (see for example Elizabeth Kolbert’s book, or this paper).

Changes in land use probably account for much modern species loss. Climate change and ocean acidification (which we’ve focused on in our work) may eventually contribute to much more. The best way to prepare for this as a society is clearly to act in ways that limit disruptions to the global environment. At the individual level, the question becomes about how to best influence the actions of societies, which is unfortunately outside of our domain of expertise.

Hi, thanks for doing this! I have a couple of questions. :)

1. What prompted you to study these topics in particular, and how do the conclusions you draw assist in combatting climate change in the present day?

2. Would you say your research has made you more pessimistic or optimistic about the ways in which governments/international organisations tackle climate change? Are we doing enough, and if not, what is our biggest drawback in this endeavour?

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If the topic is ask anything, why not be a bit academically selfish. I have an interest in Physics and specially GeoPhysics. I have done B.Tech in IT is there any chance to do Phd in the GeoPhysics and if yes, what is the procedure. If not, how can I proceed for direct Phd?

What are your go-to key points to explain that we should indeed move our asses?

A good friend of mine who is in his seventies looks at me with eyes that say “you sweet summer child, when you’re older you’ll see things are not so bleak” and calls me fatalistic because of how much time and effort I’m willing to diverge into all things climate related. I’ve built a wooden Tiny House (on wheels so I could move it closer to wherever my job would take me), am lending a (musical) hand to multiple food forests/ edible city projects, will not get on the plane even though the train will take two days and I had to cancel a job I love doing for me to avoid getting on a plane, am not planing on having children of my own and am trying to make living differently socially acceptable. I’m hopeful, because I feel the ability to change and find more joy in this new version of living. To me there’s nothing fatalistic about that.

Yet I start to question myself when he ask me why I need to make everything so difficult for myself, the world will be fine if I take the plane he says. I start explaining the tipping points and all of the things that worry me, but I am no scientist and I fear I could be using the things that caught my eye more than the more scientifically important signs on the wall. Which of course undermines credibility and leads to inaction.

Thank you for taking the time to be here, it’s greatly appreciated

Thanks for your question! Clearly the answer is to do both. But how much to each? That depends on relative costs and benefits, time horizons, how easy or hard it is to actually implement certain policy changes, etc. --- and unfortunately these are all things we have no particular expertise in. Nevertheless we think that this discussion is important; democracy probably has an important role to play here.

Thanks for your questions!

1. A large part of the answer is curiosity. We were aware of the great disruptions of the geologic past and wondered whether a quantitative theory could be devised that helped us relate past disruptions to modern environmental change. Of course were were also motivated by the practical importance of the question. But curiosity came first. Perhaps the most important consequence of our conclusions is that they’ve provided a new impetus to study the past, not just because it helps us understand how the Earth came to its pre-industrial state, but also because it helps us understand the risk of disturbing it.

2. Most fundamentally, the experience has led to a deeper respect for and interest in the people doing this important work!

Thank you!

When doing your research, have you attempted to calculate potential affects of -solar radiation management -engineered carbon removal for example DAC

If so what did you find? What are the challenges of modeling these interventions?

Thanks for your question! Promoting ecosystem flourishing on a local scale is a lovely goal, but outside of our particular expertise. And no, we’ve not read the book yet.

First, thank you for doing such important work! It’s hard for us to give advice specifically for your situation (we’d probably just ask you for your thoughts!)

Nevertheless, in case it’s helpful: we’ve found that even talking about it is useful by itself. Extrapolating from our own lives, for the little it may be worth, it seems like often a more thorough awareness of what the negative issues are can help us better deal with them.

How will doing nothing about it other than taxing the middle class further and putting increased costs on us stop this all from happening when it is third world dumps , plane traffic and ocean going vessels making the pollution way more than say anyone middle class from the USA or Europe?

Was there a large extinction event 11600 years ago as Graham Hancock and others claim?

This is extremely difficult to answer. Our own work has focused on a small piece of the puzzle: what happened in the geologic past, and how does it inform us about our problems today? But past events played out in the absence of human societies, and what could happen to human societies over long term (1000s to millions of years) is fascinating but very poorly understood problem.

What is the current rate (mm/year) of sea level rise? Is it accelerating, and if so by how much?

If ozone layer is getting better than why politicians start new agenda to curb methane? I mean why we always blame gases for global warming rather than deforestation?

What role can AI play in tackling climate change?

The ozone depletion was largely caused by CFCs. The reason the ozone is healing is a massive worldwide effort to cut the use of CFCs called “the Montreal protocol.“

I’m not sure why you’re bringing deforestation into this. Deforestation is bad, we should stop that too.

Thanks for answering and the links

I understand that the Bronze Age collapse is often attributed, in parts, to environmental disruptions. Which other collapse events in history would you attribute to climate change? When comparing these societies, do you see common strategies that perpetuated the collapse?

Thanks for this! I have three quite general questions: What methods do you use and what data do you collect to study this?

How does thresholds of catastrophe differ to the planetary boundaries framework?

Can you share your paper on the speed of change and associated volcanoes?

Have you studied about the Santa Susan Field Laboratory (old Rocketdyne facility) meltdown near Simi Valley CA that continues today to contaminate the area and it’s people with radiation? Would love to understand what you found.

Nvmd - I just realized my question is stupid.

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If you could de-extinct 1 animal b/c of it's contribution to the environment which would it be? If you could de-extinct 1 just for coolness which would it be?

And if you could de-extinct one but wouldn't b/c it knows what it did, which would it be?

What would you say is the greatest threat or plausible scenario?

There were two major volcanic eruptions in 536 and 542 AD which led to a period known as the Late Antiquity Little Ice Age. It is suspected poorer diets from poorer harvests led to the Plague of Justinian wrecking havoc with a weakened population.

While there was a decline the Avars, Sassanid and Gupta civilisations, the vacuum led to the rise of Turks, Mongols and Islam. The strategy they have in common is that, at the time, the peoples lived nomadic lifestyles on the fringes of deserts. With the Sun being ‘feeble’, as Roman senator Cassiodrus puts it, these people could be more productive during the day.

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What do you think of Graham Hancock's work?

How screwed are we?

What were your undergraduate majors, and what made you study this specfic topic?

Thanks for taking the time to do this! We need more academics offering their expertise in Reddit.

1. Is there anything individuals can do to mitigate the impact in these dire times?

2. Have you worked with policymakers? How eager are they in trying to effect change

or are they just putting on a charade?

Hey Everyone. I appreciate the chance to ask a question. This is a real question. I am in the Solar business. In fact my firm only works on the reduction and production of green energy. There is no possible way to achieve 100% renewable energy because there is not enough raw material to do so. With that said, if this is such a serious issue (affects everyone now and in the future ) why aren’t the scientist boycotting worthless industries that cause massive damage. E.g. fashion industry, movie industry, food channel, entertainment, etc… we all know first hand that these industries waste and kill millions every year. Wouldn’t it be a good start to sanction or tax these first? Outside of minimal educational pieces they are 95% worthless to the future of mankind. Second question. We all know that iPhones and technology is depleting the planet of precious resources. Most of which are outside of the US. Is the work that minorities are doing in 3rd world countries worth an iPhone? This may be outside of your wheelhouse but as a good scientist should, consider other facts that can bring this back to reality. Thank you in advance.

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How long can we go on like the idiots we are until we can't go on anymore (like the consequences are so severe that we lose most of our sacred luxury) and how long until we extinct ourselves like a little cosmic joke?

This is the only question…shame to have it ignored like this. Why waste our time with an AMA?

To be fair, this was posted 9 hours after the AMA went live. They may just not have seen it.

why argue for the lowering of CO2 when that is part of the plants food source? why do you want to starve plants and eventually starve people and animals?

Thank you for the AMA!

You said 3/4 species went extinct in the past events, does that mean there were so many species that we didn't even see? Any estimate on the number?

If a mass extinction happens in 2100, which species are in the line for extinction?

Thanks!

So… what did you find?

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How fucked we are?

How false is the assertion that this climate change is not man-made (or at least not man-catalyzed), e.g. when some say that it's a cyclical change that would have happened anyway?

Pretty false

What do you think of Randall Carlsons take on anthropogenic climate change ?

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How f#cked is the situation and can it be unf#cked in time? If so, by what means?

Doubt they don’t see it and it wouldn’t take much to reply with a response. Hopefully they do I would like to see either an agreement or fair criticism of Hancock.

What do you expect for climate havens or climate refugees in the coming 50 years?

What are your findings for the US hottest year of 1934, and the other 3 top 10 hottest years on record in the 1930's?

Could have. Wow we folow the could have science.

Whats the cyvle? Can you Show another time this happened? If not, how can it be cyclical?

Thanks for the question! Our knowledge of Graham Hancock’s work is currently limited to a few internet searches (Dan) and a few episodes of his Netflix show (Constantin), but we wanted to make sure we got around to answering this.

A first important point is that our own work focuses on catastrophes that occurred much further back in time: many millions of years rather than tens of thousands, and way before humans even evolved as a species. So our own technical knowledge is still rather different than that needed to evaluate archaeological claims about past civilizations, and to productively wade into the debate surrounding his work.

The events themselves are also rather different in scale: any extinction that may have occurred during the Younger Dryas is still relatively minor in the grand history of life (if otherwise, this would have been observed in the fossil record), while some of the events we’ve been considering genuinely wiped out a large fraction of species present at the time.

On the whole (and speaking now more generally), we do think that questions of past climate changes and societal collapse are interesting ones that deserve to be looked at. Beyond pure intellectual interest, better understanding whether/how climate changes caused collapse in the past seems quite important for humanity’s future.

Thanks for the question! See our other response here.

Thanks for your question. We think that 100% renewable energy might be an elusive goal, but anything we can do to put less CO2 in the atmosphere is of interest. As scientists we recognize that many industries contribute disproportionately to CO2 emissions. The question then becomes how to develop appropriate policies to deal with problems in which different groups may have different views as to what is important and should be prioritized. As we say elsewhere in this thread, the democratic process probably has an important role to play here.

10 - 12 inches (0.25 - 0.30 meters) in the next 30 years, which is about as much as in the last 100 years, according to https://oceanservice.noaa.gov/hazards/sealevelrise/sealevelrise-tech-report.html.

The greatest threat to humanity stemming from climate change may be the possibility of social strife (due, e.g., to displaced populations) and its interaction with a host of other problems that results in widespread warfare. This is an important but still poorly understood subject.

Maybe the most important thing individuals can do (in democracies) is to vote and support initiatives that advocate for solutions to climate change. We have not worked with policymakers but we have
much respect and admiration for their difficult work.

Among the many ways to answer this question, we’ll choose a path consistent with our topic: rates of change matter. So while plants may ultimately flourish in a world with higher CO2 levels, the fast
rates of change of our current situation risk triggering instabilities in the Earth system and/or very bad outcomes for human society.

The estimate of 3/4 largely derives from the fossil record of marine animals. And that means that if a particular fossil species has not yet been discovered, we cannot know if it went extinct.

Our own work does not predict extinction in 2100. Instead it identifies the end of the present century as a time when the total CO2 added to the oceans will likely exceed a value that in the past has been associated with mass extinctions. See also our other comment here.

Hello again and thank you for answering my question earlier. One follow up. I understand you are saying that increase in CO2 is an issue but CO2 is not a pollutant. It was present the day we were born. So why does adding CO 2 to the atmosphere hurt us? There are 400 trees for every person on earth and each tree provides oxygen for approximately 3 people. Are we at risk of O2 issues if we reduced carbon? I know the 21 to 12 % rule of oxygen inhaled, but have you measured the back end of the reduction?

I understand what you are saying but it was the democratic process that got us here. China and other countries our size do not have same regulations. Will only reducing the Western Hemisphere CO2 actually do what is needed if this is an actual crisis.

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What is the scariest, relatively unknown way that the world is likely to end in?

Thank you for raising these important questions and for expressing them through your own personal experience. Our go-to-points about CO2 emissions and global environmental catastrophe are largely made in other comments in this thread. Depending on context, other scientists will emphasize other points and other issues. We know that reducing and eventually stopping CO2 emissions is necessary for stabilizing temperatures, and also for reducing the risk of the kinds of events we’ve studied, but how to best do this and balance it with other important trade-offs is complicated and involves a number of things outside of our particular expertise. We hope that this helps at least a little.

Because deforestation is also a major threat for earth's temperature

Precisely what I was going to say

good night. you are selling your agenda. thank goodness there is a large number of scientists that disprove your agenda.

What exactly happened to cause the Younger Dryas extinction?

And what do you know? After they saw it, they responded. Incredible…

Is this planet doomed? Are we just delaying the inevitable?

Hello Dr Rothman and Dr Arnscheidt. Thank you so much for taking these questions! I am interested in following your research and that of your colleagues. Do you have any additional resources (books or papers or publications?) that we can read? I think about climate change every single day and am so glad for your work.

On a scale of 1-10, 1 being the best possible outcome and 10 being the worst, how fucked are we in the following categories?

As our civilisation stands today

As a species overall

As a planet.

how much importance do you give to observation of fungi both in the present and fungi from the past (found through archeological search) in your research ?

Got any sources?

The earth goes through periods of warming and cooling as (from what I remember) the ellipses of our orbit changes over time.

This is why we have ice ages and stuff.

Take this with a pinch of salt though because this is a 15 year old memory.

So, did you check on the cycles dates? Last time I checked we should come out of an ice age. There is also a cycle which flips the orientation of our magnetic poles or something like that. Maybe you can include that to make an argument for "non man made climate change"

The climate changes naturally. But that’s an entirely different process happening at an entirely different speed to man made climate change.

Will Earth easily be able to live her best life once all humans become extinct?

How do you find balance and personal health with all the work you collectively have to face?

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