Global Warming, History of Earth's Temperature

[Tom.G]

TL;DR Summary

We are currently at the lowest temperature ever.

According to this study published in Science magazine, the Earth hasn't been this cold for the past 350-450 million years. The Global Mean Surface Temperature took a dive about 40mya from 27C to the current 11C.

It seems like we are in the 'Golden Age' for warm-blooded animals.
The graph is in the attachment.

Original at: https://doi.org/10.1126/science.adk3705


Cheers, (?)
Tom

 

[Arjan82]

I don't know enough about climate science to know whether that study is any good or not. But I do know it doesn't matter... It's beside the point.

The earth will be fine with, say, 5 degrees Celcius increase in temperature. Life will be fine. Even many humans will survive 5 degrees of increase in temperature, no problem. However...

We are currently not well suited with our modern way of living for 5 degrees increase in temperature. That is: most people live at or around sea level, when the sea rises enough many people will be displaced causing mass migrations and thus lots of trouble. Also some places might be getting too hot to live (think Spain, Greece, Italy). Locations where we currently do agriculture may become too wet or too dry to do so, or at a lower yield. Causing huge disruptions in food supply leading possibly to lots of famine. And I'm sure there are more things that I don't think of right now.

So, in a century or two, maybe three, or whenever the temperature stabilizes again, there will still be plenty of life. I'm also sure that humans will find some way to continue to exist. But it is the road from here to there and the huge disruptions along it that I'm worried about...

 

[BillTre]

The earth will be fine with, say, 5 degrees Celcius increase in temperature. Life will be fine. Even many humans will survive 5 degrees of increase in temperature, no problem. However...

This sounds like BS.

This contradicts you earlier statement:

That is: most people live at or around sea level, when the sea rises enough many people will be displaced causing mass migrations and thus lots of trouble. Also some places might be getting too hot to live (think Spain, Greece, Italy). Locations where we currently do agriculture may become too wet or too dry to do so, or at a lower yield. Causing huge disruptions in food supply leading possibly to lots of famine. And I'm sure there are more things that I don't think of right now.

 

[russ_watters]

This sounds like BS.

This contradicts you earlier statement:

I don't see the contradiction. "Even many humans will survive..." means many humans won't and sounds consistent with "lots of famine" to me.

 

[berkeman]

I don't know enough about climate science to know whether that study is any good or not. But I do know it doesn't matter... It's beside the point.

A quick reminder that this thread is in the technical PF forums, and is subject to the technical PF rules (plus the additional Global Warming rules). Opinions without basis in the professional literature will not be allowed.

 

[BillTre]

I don't see the contradiction. "Even many humans will survive..." means many humans won't and sounds consistent with "lots of famine" to me.

Doesn't sound like life will be fine in many ways to me.
What is being described is several ecological collapses. Each can have a lot of cascading consequences some of which could be easily predicted and some not.
Its pretty trivializing and short sighted to say all that is OK, but yeah, OK.

 

[Bandersnatch]

A quick reminder that this thread is in the technical PF forums, and is subject to the technical PF rules (plus the additional Global Warming rules). Opinions without basis in the professional literature will not be allowed.

Do note, that the OP is provoking this discussion by having put 'global warming' in the title.
That processes with timescales of millions of years bear little relevance to changes counted in decades is hardly an opinion that needs substantiation in literature.
Had the OP titled the thread along the lines of 'improved assessment of Earth's past temperature', or pretty much just the title without the non sequitur of GW in it, it wouldn't look like a rehash of an old chestnut from a deniers playbook, that calls for debunking.
(Those are the optics, I'm agnostic of the intent)

 

[Arjan82]

This sounds like BS.

Do you think the earth will be sterile after global warming? In that sense I mean it will be fine. 'just another extinction event'.

But the rest of my post should convey that it will not be fine...

 

[jack action]

This is where I don't follow scientists (not science).

Science says the Earth is hotter than a century ago, and humans have roamed the Earth when it was much hotter than today (OP's study) — end of scientific facts.

Then you have these speculative words being thrown around:

some places might be getting [...]

Locations where we currently do agriculture may become [...]

What is being described is several ecological collapses. Each can have [...]

To all of this science says "We can't predict the effect of this." There are no Earth models or simulations with little humans going on with their daily lives we can study. Too many variables leading to too many potential outputs. Nothing in history too, this is totally new.

But let's be cautious and imagine the worst. (Although, who says we have to? But let's ignore this philosophical question for now.) Let's try solutions that could reverse the greenhouse gas emissions, which science says is the source of this global warming that we should fear. Again, science cannot offer guarantees for these solutions as it is still too difficult to model the Earth. But let's try them and see what we get.

We've been putting all sorts of measures to reduce emissions of CO₂ since at least the 80's. Let's take some scientific measurements and see the impact of our actions:

This curve is known as the Keeling curve, and is an essential piece of evidence of the man-made increases in greenhouse gases that are believed to be the cause of global warming. (source)

​

I don't see the slightest decrease. It doesn't even stabilize. Wouldn't that mean that our efforts have no impact on the increase in CO₂? Or is it just that 20-40 years are not enough to see an effect yet? (That may be true for Global Warming but it shouldn't for CO₂ emissions.)

I'm not sure where this next graph comes from (source), but at least it shows a drastic decline after 2019:

The cause? People slow down living to almost a stop due to the COVID pandemic. But the scientists agree that we should go back to the 1990's level to be OK. And by staying at home, doing almost nothing, we only get that little dip? Is there really a point to converting all combustion engines to electric motors, when NOT using our combustion engines has so little effect? Or wasn't the pandemic period long enough to see the full effect?

Even knowing that science agrees that the major cause of Global Warming is the rapid increase in atmospheric CO₂ caused by human activities, scientifically speaking, are we achieving something for CO₂ emissions and Global Warming? Is the stuff we're doing right now working? Can we really do something about it or is it now bigger than us and we just have to go through it, good or bad?

In other words, are the [speculative] solutions coming from scientists better than anyone else's opinion?

 

[russ_watters]

We've been putting all sorts of measures to reduce emissions of CO₂ since at least the 80's. Let's take some scientific measurements and see the impact of our actions:

​

I don't see the slightest decrease. It doesn't even stabilize. Wouldn't that mean that our efforts have no impact on the increase in CO₂? Or is it just that 20-40 years are not enough to see an effect yet? (That may be true for Global Warming but it shouldn't for CO₂ emissions.)

I think much of this is rhetorical, but I'll answer anyway: Everything done to date has had little to no impact on CO2 emissions and therefore no impact on climate change mitigation. You're right, global emissions rates haven't really even started slowing down the increases, much less dropping (caveat: unless something meaningful happened in the past 3 years that isn't in data I'm seeing yet).

But why? Well, for all the talk about action (lots and lots of talk), and a few real actions by developed nations, carbon emissions reduction is mostly in the hands of developing nations like China and India. In most developed nations carbon emission intensity (per capita or per unit of GDP) peaked many decades ago and absolute carbon emissions peaked several decades ago. But these decreases are relatively small even for most of the developed countries themselves, and are swamped by the far larger increases by developing nations. Here's a selection of some countries and the rest of the world:

The cause? People slow down living to almost a stop due to the COVID pandemic. But the scientists agree that we should go back to the 1990's level to be OK. And by staying at home, doing almost nothing, we only get that little dip? Is there really a point to converting all combustion engines to electric motors, when NOT using our combustion engines has so little effect? Or wasn't the pandemic period long enough to see the full effect?

The Pandemic period wasn't very long. Q2 had a 28% drop in GDP for the US, but it recovered most of that in the 3rd quarter; for the year it was only a 2.2% drop. And even then, the impacts weren't uniform. Driving mileage of cars dropped substantially, but did trucks/trains/ships? I doubt they changed much and some may have increased due to the boom in shipping things to peoples' houses.

Is it worth it to keep trying? It may be a matter of opinion how much we (globally) should, but one thing is not: if we want China and India to try, we have to try.

 

[hutchphd]

Wouldn't that mean that our efforts have no impact on the increase in CO2?

That is a specious conclusion. It only means what the data says: CO₂ emissions have not been much diminished. Perhaps things would be far different had no effort been made. Perhaps not.
There is only one test tube and we live in it. Demanding definitive proof before action is taken is not likely to yield a palatable result.

 

[Bandersnatch]

Is the stuff we're doing right now working?

You make it sound like somebody is following the recommendations of the IPCC. What was it, global net zero by 2050*? You're seeing that implemented?
The fossil fuels keep getting dug up at ever increasing rate, and emissions keep growing, so what would you expect? It's not that what we - the global we - are doing isn't working. It's that we're not actually doing much. The 'efforts' are mostly talk, vague promises, and creative bookkeeping. It's publicising your new solar plant with one hand, and investing in fracking with the other. It's western economies boasting of reducing emissions (by a bit, but let's not talk about that) - achieved through exporting their industrial capacity to Asia. It's companies loudly proclaiming commitment to net zero, and then weaseling out of it when a new business opportunity arises (cough*Google*cough).
At best, you can say that it could have been worse - the curves you posted could have been steeper (the climate modelling predictions for various emission scenarios has always been included in the IPCC reports, so it's not like it's divination). Well done us.

*I don't actually remember, so don't hold me on that

 

[BillTre]

Do you think the earth will be sterile after global warming? In that sense I mean it will be fine. 'just another extinction event'.

The world was not sterilized by the Chicxulub impact that ended the reign of the Dinosaurs either, so I guess that was fine, as determined by all the people around at that time. I guess that means that the earth would have to fall into the sun for some climatic perturbation to be not good.

The world was not sterilized by the Chicxulub impact that ended the reign of the Dinosaurs either, so I guess that was fine, as determined by all the people around at that time.

Poor choice of words at best.
Good AI imitation.

But the rest of my post should convey that it will not be fine...

Yeah, well there is that.
But it also conveys how you think its OK for millions to die and several great ecological disruptions to occur. That's just fine!!!

 

[Arjan82]

Yeah, well there is that.
But it also conveys how you think its OK for millions to die and several great ecological disruptions to occur. That's just fine!!!

Alright... note to self: sarcasm really Really doesn't work in written language... I mean, the whole point you are making is exactly the same as I was trying to make using my silly idea of humor. I absolutely do not think it is OK at all!

Poor choice of words indeed I guess.

 

[BillTre]

Alright... note to self: sarcasm really Really doesn't work in written language... I mean, the whole point you are making is exactly the same as I was trying to make using my silly idea of humor. I absolutely do not think it is OK at all!

Poor choice of words indeed I guess.

Actually, I am a generally sarcastic person, so I feel for you.
There are emoji sarcasm indicators (like maybe or
) one could use, not that I am good with them.

However, there were those who took your interpretation seriously, so don't get sarcastic with GW.
I support the the ecosystem.

 

[Frabjous]

Here’s a fun plot on energy usage.

The author is arguing against the concept of successful energy transition.

from “More and More and More” by Fressoz

 

[gmax137]

Have you read this book? When I look on line it says "available August 2025."

 

[DOGE3500]

If you think heat is bad, wait until this graph bottoms out.

 

[Frabjous]

Have you read this book? When I look on line it says "available August 2025."

I have started the British edition.

 

[pinball1970]

A slight aside, some positive initiatives below including investment in clean energy.

https://www.canarymedia.com/article...ew-record-with-71b-in-clean-energy-investment

https://phys.org/news/2024-12-good-humanity-combat-climate.html

 

[PeroK]

A slight aside, some positive initiatives below including investment in clean energy.

https://www.canarymedia.com/article...ew-record-with-71b-in-clean-energy-investment

https://phys.org/news/2024-12-good-humanity-combat-climate.html

The growing CO2 emissions data in a previous post proves that, as a species, we haven't even started doing anything meaningful yet. And, it's seems likely that we will hit +1.5C this year. As I understand it, that was supposed to be the limit that we must not reach. We've reached it already, have we not?

If we had been serious about tackling climate change, then we would have changed our lives radically over the past 40 years - and fundamentally looked for contentment in life from things other than gross over consumption. This is the fundamental problem. I can ask myself: what have I personally been required to sacrifice in order to reduce my carbon footprint? The answer is precisely nothing. Not one single thing. I'm free to produce as much CO2 as my modest wealth will allow.

The ony thing you can say is that perhaps it could have been worse. We haven't actually made the situation as bad as possible. You could give us some credit for that, perhaps.

 

[gmax137]

The growing CO2 emissions data in a previous post proves that, as a species, we haven't even started doing anything meaningful yet.

Yeah, but we're about to begin to start to get ready to commence...

 

[pinball1970]

As I understand it, that was supposed to be the limit that we must not reach. We've reached it already, have we not?

Yes, that's my understanding.

 

[hutchphd]

Yeah, but we're about to begin to start to get ready to commence..

I believe that we have already begun to to start to get ready to commence.......hence the palpable backlash. No worries.

 

[D H]

According to this study published in Science magazine, the Earth hasn't been this cold for the past 350-450 million years. The Global Mean Surface Temperature took a dive about 40mya from 27C to the current 11C.

That is not quite correct. The current Global Mean Surface Temperature is 15 °C, according to NASA, and according to many other sources. The granularity of that study means the last 11700 years (when the last glaciation ended and the Holocene began) barely registers in the terms of that study. The study does not see the difference between the last 11700 years and the glaciation that immediately proceeded it in the Pleistocene. The temperature change over the last 50 years, while smaller in scale than the temperature change since the last glaciation ended -- that isn't even a blip on the timescale of the cited study.

It appears the cited paper switched granularity, possibly multiple times. It definitely does not have good insight into the climate variations during the Karoo ice age, so it is hard to say that the current ice age is colder than the Karoo. That said, that might well be the case. During the Karoo there were no land masses near the North Pole. The Karoo was mostly a Southern Hemisphere event. The current icehouse started around 33 million years ago (mya) when Antarctica started icing over, started to get seriously cold about 10 mya when Antarctica completely iced over, then got colder yet when the Northern Hemisphere joined in on the fun about 2.5 mya, then got colder yet about 1 mya when the glaciation cycle changed from 41 thousand years to the current 100 thousand years.

One last item: It is in general not a good idea to place undue credence on a single very recent peer-reviewed report, even one printed in a journal as prestigious as Science. This paper does after all conflict with other reconstructions. It's best to wait until the scientific dust settles, and this typically takes well over a year.

 

[jack action]

@D H 's comment shows why I don't like how we present a lot of stuff as "proven by science" when not all "sciences" are equal.

There is what I could call "pure science" and "statistical science".

With pure science, you define initial conditions and a set of mathematical rules, which should predict a result. If you do many experiments with precise measurements, you should end up with a 99.9999% success rate (or something in that order) to call it "scientifically proven". The 0.0001% can be assumed to be within the measuring error.

In statistical science, we usually conduct many experiments, find a pattern, and evaluate the success rate using statistics. We are usually satisfied with success rates way below 100%, sometimes in the 70-80% range, if not lower. The experiences may have been conducted with the "scientific method" but the results cannot be considered "scientifically proven". We may be on the right path to understanding but we are clearly missing something.

There is a difference between what is proven by basic physics and, say, a clinical trial. There are often a lot of holes in the latter. For example, people who smoke have a lower life expectancy, but that does not mean all smokers die young. (And the opposite goes for non-smokers.) You don't need to do an extensive study to see that, anyone can.

And this is how we end up with people throwing all science out the door, thinking "Science is science" and if we cannot trust one, we cannot trust all of them. "My uncle smoked all his life and died at 92 from a fall in the stairway, then the Earth must be flat!"

I hate when medical and climate studies are put at the same level as other purely mathematical studies with a higher success rate. Especially when governments make decisions for everyone based on them. It's a rebellion waiting to happen.

 

[BillTre]

Modern large scale science involves not only interactions between doing the science and government regulators, but also the politicians getting elected and the political bases they employ (which are varied and not always emphasizing accuracy) in their elections. When the government gets involved, things can be a lot more complicated.
Politicians are often motivated by their contributors.

 

[hutchphd]

I hate when medical and climate studies are put at the same level as other purely mathematical studies with a higher success rate. Especially when governments make decisions for everyone based on them. It's a rebellion waiting to happen.

I think you do a disservice to the scientific method by drawing such a sharp dichotomy. In principle the the scientific method is the same. We are simply better at some branches than others. All science involvers measurement and statistical inference, but for the flight of a projectile the systems are simple for our brains to apprehend. The fact that we expect other systems to be consistently trivial should not serve as an indictment of the method. One needs to understand the limitations. Don't shoot the messenger . Or toss out baby with the bathwater....(insert hackneyed phrase here)

 

[D H]

@D H 's comment shows why I don't like how we present a lot of stuff as "proven by science" when not all "sciences" are equal.

Nothing is proven by science, and that includes physics. The best that science can do is equivalent to the legal concept of "proven beyond a reasonable doubt." There is always a black swan problem in all of the sciences, and that includes physics. There are biases as well.

There is what I could call "pure science" and "statistical science".

That you agreed with me for all of the wrong reasons is a bit alarming to me. Perhaps my writing needs improvement. All of the sciences, and that most certainly includes physics, rely heavily on statistics. There is no such thing as your imaginary "pure science."