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4.2 Kiloyear Event (wikipedia.org)
136 points by smacktoward on Dec 16, 2019 | hide | past | favorite | 97 comments

Naming things is hard.

Current name is relative to current date because it talks about an event 4200 years ago. Any literature discussing this will be stuck with this relative name and eventually will become incorrect.

I understand why they don't want to use BC to name a global event that touched all cultures, and far before C was a thing.

Maybe it would make sense to adopt kurzgesagt's Human Era calendar, starting at approximate time of first human settlements. They call current year 12019.

Not exactly. A word "BP" in the full name ("4.2-kiloyear BP event") is a key: it stands for "Before Present", where the "Present" is defined as 1 Jan 1950 for the archaeological and geological purpose [1].

[1] https://en.wikipedia.org/wiki/Before_Present

So when Marty went back to 1955, that actually was The Future, archaeologically speaking.

Why do you think it's called `back to the future`?

maybe because he wanted to go back to the future after getting slightly displaced

BP can be read as "Before Pollution by airborne radioactive isotopes made radiocarbon dating unusable"

or "British Petroleum"

Present being defined as 1950 strikes me as exactly the sort of problem that GP was trying to avoid.

The middle of the period called "modern art" seems to be about 1915.

Modern is not a synonym of contemporary. We're currently in the late stage of the postmodern period.

Postmodernism has been around for a long time. It appears at least some people think it's firmly historical and not contemporary...and that opinion is from almost a decade ago.

Yeah, I considered that, but I couldn't think of a new philosophical movement that's replaced it, so chose to say that we're in a late phase of postmodernmism. The important point is that modernism is firmly in the past.

EDIT: Early Modernity began around 1500 and Late Modernity (allegedly) ended in 1989. I think Postmodernity still has a few years left to play out.

I'd never heard of that before... I like it.

So BP = C + 1950, and this is better how ? Seems worse really, why not just stick with C ?

BP specifically means that the date was calibrated [1] after radiocarbon dating. It is not just an epoch difference.

Also, the radiocarbon dating itself (and thus the beginning of effective absolute dating) was invented around 1950, and nuclear weapon tests made everything after that point unsuitable for the radiocarbon dating. It would be natural to have that point as a reference for the "present" at least for now.

[1] https://en.wikipedia.org/wiki/Radiocarbon_calibration

I actually never thought about the fact that human nuclear testing would basically destroy the accuracy of radiocarbon dating. Any distant future civilizations who assumed there had never been any ancient sources of distortion would end up with results that are way off. Of course, that’s true of us as well.

Technically we are still able to use radiocarbon dating for dates after 1950, at the reduced accuracy though. This is what I meant by "unusable", because other dating techniques will work better.

The calibration is there because the global 14C/12C ratio is not constant over the time, and the same procedure can be used given the recent history of ratios (that we do have). As far as I know, though, resulting error bars might be much larger than usual because the function from uncalibrated ("14C") years to calendar years is no more regular. For example see [1] where uncalibrated t2 and t3 can correspond to much larger periods than t1's; historically this happened only locally, but after 1950 it would be far more common. Still the radiocarbon dating can be used with this caveat [2].

[1] https://commons.wikimedia.org/wiki/File:Variations_in_calibr...

[2] https://www.nytimes.com/2011/03/29/science/29qna.html

Right, right, a new calendar system starting at the dawn of the Atomic Era.

That way we can have another shot at it being 1957.

It's better in the way that radio-dating kind of broke once we figured out fission and started nuclear weapons testing, so the early post-war years are quite important to people who use that technique.

Exactly this: it is a permanent mark on the strata: below this, radiocarbon dating works, provided no leakage fom above; above, not.

I guess it's just because the difference between BC and BP is irrelevant for most archeological and geological purposes, and referring to a specific year for something that happened 200 million years ago doesn't seem to make much sense, so "present" is a suitably vague indication. But then you have special cases like this one, recent enough that the difference is actually 50%, and you need to specify a more precise time point for present. So, as an afterthought, you decide that "present" is 1950, but you still use a uniform scale for all events.

Well now that makes a bit more sense.

Any date epoch using calendar years as a unit is going to be C + X for some (positive or negative) X.

That depends on your calendar. Some calendars average around the same time as the gregorian calendar, but can deviate significantly on shorter time scales (e.g. the Hebrew calendar, which uses lunar months and leap months to keep rough track to a solar calendar). Other calendars have more deviation - for instance, the Islamic calendar merely approximates the solar year with moons on a single year timeframe, so it moves about 10-12 days a year and just accepts that in some years, Ramadan will be in winter and in others it will be in summer.

Moreover, even our calendar and epoch has changed. Since Jesus pbuh was conceived nine months before he was born, the English used to record the beginning of the year as the 25th March OS before they adopted the Gregorian calendar. Therefore, the 20 March and the 30 March of the same year would have different numbers. (The general public still celebrate new years on the 1 January in this period, which can make dates between new years and lady day ambiguous.)

So unless you circuitously define a "calendar year" to mean "the calendar used for measuring compared to C", your statement is false. If you circuitously define it, it is a useless statement which says nothing more than "true statements which can be made about calendar length are true", which is unnecessarily specific while being at the same time redundant.

"Jesus pbuh was conceived nine months before he was born"

I thought he was conceived 4-5 years before he was born, if you're going to nitpick.

Why is BC bad because this event touches all cultures? Every part of science and academia is effected by the culture doing the research, and is almost its own fascinating historical record in itself. Trying to make everything as generic as possible is bland and boring.

The reason BC is bad is because, when you hear BC, you think, oh this has been calibrated by knowledge of the passage of time according to records by humans. So perhaps we know it happened in year 20 of the reign of King B, and we have enough other information to believe that means about 125 BC.

But the date of this event was determined by radioactive calibration. It's not measuring the same thing. It measures something that approximates human years.

This might seem like a trivial distinction to lay people, but it's relevant to the field, and the 4.2 k BP year event is a technical term.

> Trying to make everything as generic as possible is bland and boring.

This is subjective.

On the other hand going with a generic choice helps create a well defined universal language. This makes scientific cooperation across cultures easier.

Sample difficulties of going with culture-specific naming: https://en.m.wikipedia.org/wiki/Comparison_of_the_imperial_a...

> Naming things is hard.

> Maybe it would make sense to adopt kurzgesagt's Human Era calendar, starting at approximate time of first human settlements.

So what about calling it the settlement era, as humans were around before the first settlement, making "human era" a bad name to begin with. :)

https://en.m.wikipedia.org/wiki/List_of_periods_and_events_i... 'List of periods and events in climate history'

I love learning about past Earth climate history and just history in general. One of my mind blowing climate events is:


It's not in the list you link, but it's a pretty neat read. Basically, the Mediterranean dried up and refilled about 6 million years ago.

And it's five kilometres deep.

One of the best XKCDs ever is sort of related:


These are very interesting. They do not get covered very often, but these events show climate changes in precipitation and temperature occur on the regular and cause even dramatic events (like the drying of the Sahara) naturally. I'm still trying to piece together what impacts geomagnetic excursions and reversals have on climate. During the last reversal 780,000 years ago the winter Asian monsoon was about 3x stronger than today according to one study I read.

Historical civilisations were very vulnerable to changes in local climate as they were heavily reliant on local food production, whereas we routinely ship food across oceans. Events like the [Little Ice Age](https://en.wikipedia.org/wiki/Little_Ice_Age) barely show up in the global climate record.

Earth's climate has varied greatly over time but its the current rate of change that is so alarming. During the last ice age it was about 4.5 degrees colder but it took 10,000 years to reach modern temperatures. We're currently on a path to changes of that magnitude within the next 70-100 years.

You're incorrect about your assumptions. If you click the link in the parent post, you'll see that temperatures swung as much as 8C during the ice age. These events are called Dansgaard-Oeschger events (https://en.wikipedia.org/wiki/Dansgaard%E2%80%93Oeschger_eve...) The warming would happen rapidly (within 3 decades), followed by a stepped down cooling period (often lasting hundreds of years). This happened repeatedly during the most recent glacial.

And then more recently, after the last glacial period had ended, you had incidents like the Younger Dryas, for example, where temps plunged to near ice age levels (up to 6C drop in a few decades) and then rapidly warmed all of a sudden. If you read https://en.wikipedia.org/wiki/Younger_Dryas) some are suggesting that a warming episode at the end of the Younger Dryas occurred in as little as a few years and warmed global temps by 7C.

Note, that by the end of the Younger Dryas, the Arctic was as much as 7C hotter than it is today (https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019...).

There's thousands of papers on the Little Ice Age. It certainly shows up all over the world in the fossil record. https://www.sciencedirect.com/search/advanced?qs=little%20ic...

"But there have been several times in Earth’s past when Earth's temperature jumped rapidly, in much the same way as they are doing today. Those times were caused by large and rapid greenhouse gas emissions, just like humans are causing today. In Earth's past the trigger for these greenhouse gas emissions was often unusually massive volcanic eruptions known as “Large Igneous Provinces,” with knock-on effects that included huge releases of CO2 and methane from organic-rich sediments. But there is no Large Igneous Province operating today, or anytime in the last 16 million years. Today’s volcanoes, in comparison, don’t even come close to emitting the levels of greenhouse gasses that humans do.

Those rapid global warming events were almost always highly destructive for life, causing mass extinctions such as at the end of the Permian, Triassic, or even mid-Cambrian periods. The symptoms from those events (huge and rapid carbon emissions, a big rapid jump in global temperatures, rising sea levels, ocean acidification, widespread oxygen-starved zones in the oceans) are all happening today with human-caused climate change. The outcomes for life on Earth were often dire. The end Permian extinction saw around 90% of species go extinct, and it left tropical regions on the planet lethally hot, too hot for complex life to survive. The Triassic extinction was another, one of the 5 biggest mass extinctions in the geological record. Even in the end Cretaceous extinction, in which dinosaurs were finally wiped out by an asteroid impact, a major global-warming extinction event was already underway causing a major extinction within 150,000 years of the impact. That global warming 66 million years ago was due to catastrophic eruptions in India, which emitted a pulse of CO2 that sent global temperatures soaring by 7°C (13°F).

So yes, the climate has changed before, and in most cases scientists know why. In all cases we see the same association between CO2 levels and global temperatures. And past examples of rapid carbon emissions offer no comfort at all for the likely outcome from today’s climate change."


> ...you'll see that temperatures swung as much as 8C during the ice age. The last glacial period itself covers some 100,000 years.

I could have phrased it better, I'm talking about the temperature difference between the end of the last age and the current day.

> ...Dansgaard-Oeschger events

The recorded temperature swings are local rather than global, global temperature does not rise by five degrees in a matter of decades unless something catastrophic happens.

> There's thousands of papers on the Little Ice Age. It certainly shows up all over the world in the fossil record.

Yes, but average global temperatures were barely affected.

And what was the effect of that on animal life? Not great: https://en.wikipedia.org/wiki/Quaternary_extinction_event#Pl...

Thats why I hate these Greta style "climate activists", since they only focus on climate, as if thats the only bad shit going on concerning environment. And even so, they are wrong about "apocalypse" style of events.

Even if you solve atmospheric conditions, CO2 and temperature, still you have the pollution of the waters, mass extinctions due to habitat loss, car-tyres rubbering off everywhere, unknown untested toxins even on your cloths. Thats like, not talked about.

EDIT: Cant believe somebody downvoted you. Yes nature has done fast changes, faster than human-induced change currently, and "nature" has mass-exterminated most of its life several times over, and other forms of life caused the deaths and biological disaster for most of other life on earth as well. These are facts.

Somehow these Greata climate activists, would like to believe that humans are more powerful in their destruction than cyanobacteria. Wishful thinking really.

Your argument being? That human-induced global warming affecting the life of millions, potentially billions of people, should be ignored because worse has happened in Earth's history? Because humans also adversely affect different parameters of the environment?

Also, it is easy to pinpoint this issue to a little girl from Sweden, but unfortunately she is just repeating the general scientific consensus. Harder to argue against that, is it?

"Harder to argue against that, is it?"

I'm beginning to think that countering illogical arguments with logical ones is actually some kind of tactical error in many situations - I have no idea what the alternative is but I increasingly feel that it is too easy to goad people (particularly those with some kind of scientific training) into types of arguments that really don't resonate with a lot of people.

> Your argument being? That human-induced global warming affecting the life of millions, potentially billions of people, should be ignored because worse has happened in Earth's history? Because humans also adversely affect different parameters of the environment?


My argument is, fuck the climatists, and their self-good crusade, since its not good, and their suggested solutions would actually cause more poverty and hurt poor people more.

My argument is, the rich are the problem, not pollution per se. 0.1% of the world population can pollute and destroy the environment of the rest. They can even ensalve the rest without destroying the environment.

Thats where the problem lies, oppression of the very few on the many, thats the problem we need to solve. The "climate atmospherists" are a side-show, stealing the light from the real issues.

EDIT: scientific consensus

Im not arguing against sci consensus, this climate issue is not "science" its politics, and should be treated as such. Everything is politics, remember that.

What makes you think she doesn’t care about other aspects of the environment? She’s just focusing on climate change because it has an effect on all of those things too.

Indeed. "Greta is focusing on the wrong things, therefore we should do nothing" is a terrible argument.

Thats not my argument, if you listen carefully to all climatists, they are trying to reduce the scope of the issue down to CO2.

They are trying to use soft means like climate meetings and "targets of CO2", instead of spurring eco terrorism and beginning violence to save the planet. Thats a terrible path to take, to just "lets hold each others hands and sign really nice and come to a solution".

When the problem is caused by the same oppressive relationships now as it was 2000 years ago - slavery, and can only be solved with violence.

> Even if you solve atmospheric conditions, CO2 and temperature, still you have the pollution of the waters, mass extinctions due to habitat loss, car-tyres rubbering off everywhere, unknown untested toxins even on your cloths. Thats like, not talked about.

Have you been living under a rock? They're talked about all the time.

So your opinion just happens to benefit the fossil fuel industry and requires no effort on your part? Is that a coincidence?

No, my opinion does not benefit fossil fuel industry, my opinion is - we should burn the gas stations to the ground, stick a potato up every SUV you see, toss tyre-destructing spikes on every road.

Kidnap CEOs of the fossil fuel industry, and citizen-jail Monsanto managers, you know... disruption.

The fossil fuel industry is not inherently bad. You understand that prior to the invention of the internal combustion engines and electricity, the world was a really rough place. Life expectancy has more than doubled in the last 120 years. And natural disasters aren't even in the top 50 ways to die in 2019. A 100 years ago, more than a million people a year were dying from natural disasters. Last year, it was 11,000 worldwide. That is despite the human population going up 8x in that timeframe. It is not the crisis that people are hyping it up to be.

The risk is not only from natural disasters directly, but the changes in habitability that show up as a result, and the refugee flows and resource wars that are expected to happen.

“Even if you solve atmospheric conditions, CO2 and temperature, still you have the pollution of the waters, mass extinctions due to habitat loss, car-tyres rubbering off everywhere, unknown untested toxins even on your cloths. Thats like, not talked about.”

This is how I know you've never engaged seriously with climate activists. These things are definitely talked about.

Agreed, I think there's bigger problems than mild warming. As far as I can tell, mild warming is usually good for the human race and for ecological health, such as plant growth.

For example, leaf area index has increased by 8% since the 80s. CO2 is fertilizing plant growth.



If you listen to a lot of the hype, it seems it's all bad, when really it's a mixed bag of complex trade offs.

This is a common denialist point and is unfortunately a massive oversimplification, there is a hard limit to this increase. Plants are limited by far more than co2


There's a good deal of observation bias at play here.

We currently track the "average annual daily global mean temperature" to somewhere around 4 digits of precision, with an accuracy of around 3 digits of precision (back in the day my university TAs would fail any lab report with inverse precision like that, but I'm no PhD in climate science), and with a time frame of hours. Estimated historic temperatures are presented with 2 or 3 digits of precision over a timeframe of centuries or kiloyears.

Saying current trends are unprecedented is motivational and technically correct, but not scientifically sound given the actual data. Well, science as in hard sciences like chemistry and physics in which we could run controlled experiments to generate confidence in our understanding; not soft sciences like economics or nutrition where controlled experiments would be unethical and results are only as good as the next product you're selling.

My point is that you can see the current short-term trends because we have precision and accuracy to be able to do that. We lack the precision and accuracy of historical data to be able to do that, which makes it an argumentum ad ignorantiam.

What is the likely cause of this event?

I love reading these kinds of wikipedia articles especially when it comes to reprecussions on ancient civilizations.. anyone got a book suggestion for s/t more detailed?

Best book on the subject I read is Wright's "A Short History of Progress" https://www.amazon.com/Short-History-Progress-Ronald-Wright/... Jared Diamond's "Collapse" is in a similar vein, but less cleanly written.

What will this be called in 100 years?

"Because the present changes every year, archaeologists, by convention, use A.D. 1950 as their reference. "

Climate change over time.

The chart in the article makes recent man made global warming look insignificant compared to recent changes. Much different than the often sited xkcd, https://xkcd.com/1732/, which shows the same time period as basically a flat line. Who is right?

Both, one is a single data point at a single location, the other is global trend. The medieval warm period wasn‘t warmer than the average on average either, it was just a local fluctuation.

According to this[1] that graph is frequently used by climate skeptics but it is outdated and incorrect.

[1] https://www.carbonbrief.org/factcheck-what-greenland-ice-cor...

Chart in xkcd is for global and smoothed temperature (proxy measurements with 200 years resolution), so it downplays abrupt and regional temperature changes like in Greenland or Younger Dryas


All the events in the wikipedia articles are localized, whereas the current global warming is a a global event, which is what is referenced by xkcd.

What this means is that the frequency and/or the intensity of these local outlier events can increase significantly. This is what man-made climate change means and we can still avoid most of the negative effects if we want to.

Often these local climate change events are taken as proof that 'climate has always changed'. Well, yes of course - but not on a global scale during human civilization as we know it.

Personally, imagining these events occuring during our lifetime, maybe several at once or just a couple of decades apart scares the crap out of me.

"we can still avoid most of the negative effects if we want to"

There is (possibly a minority) view that no, we can't, and things are far, far worse than people think. That contrary to the idea that people exaggerate the threat, in fact it's been minimized to the point where we are about as prepared for it as we would be for a large asteroid strike.

Climate change over time. Earth actually experienced more than '4.2 Kiloyear Event'.

1.「4.2 Kiloyear event」 - A severe aridification event, occurring around 2200 B.C., that greatly contributed to the fall of the Akkadian empire.

2.「Medieval Warming Period」 - A warmer climate experienced especially in the Northern Hemisphere when Vikings and Inuit were moving to Greenland, around 800-1300 A.D.

3.「Little Ice Age」 - A cooler climate that eventually caused the demise of the Vikings, lasting from circa 1300-1850 A.D.

4.「The Holocene Era」 - Starting about 10,000 years ago, this era includes the Medieval Warming Period, the Little Ice Age, and continues all the way up until today!

Seems like evidence that our current climate change might be random.

How do you rule out random climate variation scientifically? I'm curious, do we have enough data to say one way or the other?

I'm hesitant to post this, since it seems like detached scientific conversation about climate change has been in short supply. But perhaps.

For me – scientifically-minded layperson, but not a climate scientist – the issue seems to be that people have conflated & confused two issues. One: that the climate was, without argument, different in the past. Two: that we are now, without argument, influencing the climate due to the extraordinary amount of carbon dioxide that we are producing.

One does not preclude the other. Was the climate different, often hotter and drier, in the past? Sure. Evidence shows that it was.

But does that mean that we aren’t leading ourselves in to a short/medium-term catastrophe by dumping enormous amounts of CO2 in to the environment now? No. The two are unrelated.

Imagine if we determined that the climate was on a natural cycle, such that the entire Earth would warm, fires and droughts would become commonplace, and that sea levels would rise as a result of global temperature. Would we just do nothing? I’d hope not. I’d hope that it would spur us in to action, to realise that our quality of life is about to radically change, that human migration will necessarily increase, that people living near the sea, or depending on water, will have their lives irrevocably changed.

That has happened in the past. We just didn’t have such a complicated society at the time, so the impacts were less. If you count the extinction of the Egyptian society as “less”.

It’s also happening now, except we are doing it. Voluntarily, with full knowledge of the ultimate result.

That seems, to people like me, a bit silly.

Shouldn't the default assumption be that humans are affecting the climate and there is an underlying natural trend, and that adds significant uncertainty to the magnitude and sign of those two factors?

People always seem to talk as though it's one or the other, but it seems to me essentially impossible that it's not both.

> Shouldn't the default assumption be that humans are affecting the climate


> and there is an underlying natural trend,


> and that adds significant uncertainty to the magnitude and sign of those two factors?

Ooh you were so close to the trifecta.

Nobody has ever convinced anyone of anything in the history of the universe by affecting an air that you're too smart to explain why you're right.

The warming of our atmosphere is easily predicted by basic science related to greenhouse gasses and solar radiation.

This isn't disputable as randomness any more than an object can be said to have randomly fallen to the ground when dropped.

Here is one of countless sources you can find that explain this principle and the consequences: https://www.climate.gov/news-features/understanding-climate/...

>In fact, the last time the atmospheric CO2 amounts were this high was more than 3 million years ago, when temperature was 2°–3°C (3.6°–5.4°F) higher than during the pre-industrial era, and sea level was 15–25 meters (50–80 feet) higher than today.

Doesn't this mean that the correlation between CO2 levels and temperatures isn't that big?

I can come up with a couple alternatives to your explanation:

1. Our current carbon levels haven’t been high long enough for their total effects in temperature to be felt yet, given the size of the system they must affect. 50 years is a blip on geological timescales.

2. There are cascading effects to high CO2 levels that will take longer to manifest themselves and which will raises the temperatures further. Permafrost melting and releasing methane is a possible example.

The orbit of the earth around the sun, and the activity of the sun itself are also possible culprits. I'm sure actual climatologists have a better explanation.

The correlation has a significant lag on it because of the huge thermal capacity of water and the even bigger latent heat capacity of ice melting. The antarctic ice sheet will take a long time to melt.

It doesn't have to be large if you throw enough CO2 and other greenhouse gasses into the lower atmosphere, it just has to correlate. Far more concerning is the rate of change, which is unprecedented. There could be unforeseen impacts from the speed, and a new equilibrium from the already achieved temperature increase could be hundreds of years away as billions of cubic kilometres of ice takes a while to melt. 2C by 2100 is a reporting convenience.

Ozone depletion measured CFCs in parts per trillion (US short scale).

There are plenty of resources on the topic and prior discussions on HN. People really don't want to rehash them because 1. it gets boring and 2. it leads to flamewars.

You ask "do we have enough data". Well, the same data that gives us evidence of prior climate events is the same data that shows human emissions are climatologically significant. So if we have enough data to study random changes, we have enough to study the changes we are causing.

If you want to take a stance against man-made climate change, you'll actually need to do your own research first and have a really good reason why it's wrong. Can you yourself list all the data sources that go into climatology and why they aren't adequate?

I don't think I took a stance against anything. I think I asked a couple of questions.

I had a longer comment prepared, but as you say, responding to accusations tends to get boring.

If you want to have a conversation about this, though, it would be nice.

How much of the IPCC reports have you read? It would indicate where the appropriate starting point for the conversation is.

For anyone coming to this conversation now, the IPCC Summary for Policymakers Report[1] is absolutely required reading before you can have any opinion on climate science. It's not a hard read, put aside an afternoon for it, you won't regret it. It's written by actual climate scientists, for an audience of laypeople.

[1] https://www.ipcc.ch/srocc/chapter/summary-for-policymakers/


Please don't be a jerk on HN, regardless of how wrong or annoying you feel another comment is.


Oh, I'm on "Y Combinator", eh?

Look sonny, I've been on HN since 2008. I guarantee you that people in the early days would have been nice about this topic.

My options here are to sit quietly and let people take turns kicking me in the stomach merely for asking a question, or to exit the conversation. I'll do the latter.

Have a good week.

As another long-time HN user and as someone myself who has previously held opinions which evidence eventually led me to change, I want to give you the benefit of the doubt.

In this thread you've been responding more to the meta comments than to the actual data people have posted. In a hot-button topic like this, that leads people to believe you are acting in bad faith. Do you have any response to the IPCC report, or to the other comments about CO2 and temperature data?

Here's all the likely causes of warming - earth's orbit, sun, aerosols, volcanoes etc each overlaid on observed over the last 125 years as you scroll down. You decide.


> Seems like evidence that our current climate change might be random.

To me, it seems like (strong) evidence that climate can change.

And that there is a cause of this change, and that the cause that can be found. Maybe volcanic, meteoric, related to vegetation levels, or other?

Which is, I think, the _opposite_ of random. It is understandable and predictable.

> How do you rule out random climate variation scientifically?

Outside of quantum physics, "it was random" is not a scientific explanation. Science finds causes.

When applied to "our current climate change", the idea that climate can change and change a lot, in response to causes, well, that provides the opposite conclusion to yours doesn't it: we can see the causes this time.

It's not that it's random. It's that it is a non-linear, dynamic system. What that means is that if you have the perfect climate model (which, we don't) and you're off on your input of the parameters to that model by the slightest bit, the outcomes will veer off wildly from modeled expectations.

Doesn't that apply to weather much more than it does to climate?

Climate is just the average of weather over a long period of time. It applies to both. The only difference is the units. There are hundreds of cycles and factors that influence climate. We don't have all of them modeled, nor quantified. So there are unknown unknowns.

> The only difference is the units

Negative. It's quite possible (even likely) that the odds of a major hurricane hitting Florida next week are down to "a non-linear, dynamic system" and you're tying to predict which why the storm will "veer off wildly", while the average number and total intensity of storms over the next ten years is neither of those.

We can directly measure that there has been a large increase in the amount of greenhouse gases in the atmosphere. It's extremely well established both experimentally and theoretically how the responses of greenhouse gases to different frequencies of electromagnetic radiation lead to warming. We can probably also actually measure the energy coming in from the Sun, and with satellites measure the amount going out, to further verify that the greenhouse gases are behaving as expected.

That allows us to reduce your question to how do we rule out that the increases in greenhouse gases are due to random variation?

For CO2, we can answer that by looking at different carbon isotopes. CO2 in living plants, CO2 in long dead plants, CO2 in volcanic gas emissions, and CO2 from weathering rock all have distinctly different ratios of carbon isotopes. By looking at the isotope distribution on the carbon in the atmosphere, we can show that most of the increase is from long dead plants--in other words, from burning coal and oil.

In what way is this evidence against man made climate change?

Intense, world-changing climate change has been with us since long before fossil fuels. This is yet another instance.

I am interested in the scientific methodology that rules out such variations and confirms that fossil fuels are in fact responsible.

The time period is an obvious one: we seem to be seeing spikes in one century vs millennia. But the details of those spikes matter in comparison to our total historical record; hence the curiosity.

This xkcd shows the long time graph into perspective with relevant notes : https://xkcd.com/1732

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