Arguments
What does past climate change tell us about global warming?
What the science says...
| Select a level... |
Basic
|
Intermediate
| |||
|
Greenhouse gasses, principally CO2, have controlled most ancient climate changes. This time around humans are the cause, mainly by our CO2 emissions. |
|||||
Climate Myth...
Climate's changed before
Climate is always changing. We have had ice ages and warmer periods when alligators were found in Spitzbergen. Ice ages have occurred in a hundred thousand year cycle for the last 700 thousand years, and there have been previous periods that appear to have been warmer than the present despite CO2 levels being lower than they are now. More recently, we have had the medieval warm period and the little ice age. (Richard Lindzen)
At a glance
Just imagine for a moment. You fancy having a picnic tomorrow, or you're a farmer needing a dry day to harvest a ripe crop. So naturally, you tune in for a weather-forecast. But what you get is:
“Here is the weather forecast. There will be weather today and tomorrow. Good morning.”
That's a fat lot of use, isn't it? The same applies to, “the climate's changed before”. It's a useless statement. Why? Because it omits details. It doesn't tell you what happened.
Climate has indeed changed in the past with various impacts depending on the speed and type of that change. Such results have included everything from slow changes to ecosystems over millions of years - through to sudden mass-extinctions. Rapid climate change, of the type we're causing through our enormous carbon dioxide emissions, falls into the very dangerous camp. That's because the faster the change, the harder it is for nature to cope. We are part of nature so if it goes down, it takes us with it.
So anyone who dismissively tells you, “the climate has always changed”, either does not know what they are talking about or they are deliberately trying to mislead you.
Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!
Further Details
Past changes in climate, for which hard evidence is preserved throughout the geological record, have had a number of drivers usually acting in combination. Plate tectonics and volcanism, perturbations in Earth's slow carbon cycle and cyclic changes in Earth's orbit have all played their part. The orbital changes, described by the Milankovitch Cycles, are sufficient to initiate the flips from glacials (when ice-sheets spread over much of Northern Europe and the North American continent) to interglacials (conditions like the past few thousand years) and back – but only with assistance from other climate feedbacks.
The key driver that forces the climate from Hothouse to Icehouse and back is instead the slow carbon cycle. The slow carbon cycle can be regarded as Earth's thermostat. It involves the movement of carbon between vast geological reservoirs and Earth's atmosphere. Reservoirs include the fossil fuels (coal/oil/gas) and limestone (made up of calcium carbonate). They can store the carbon safely over tens of millions of years or more. But such storage systems can be disturbed.
Carbon can be released from such geological reservoirs by a variety of processes. If rocks are uplifted to form mountain ranges, erosion occurs and the rocks are broken down. Metamorphism – changes inflicted on rocks due to high temperatures and pressures – causes some minerals to chemically break down. New minerals are formed but the carbon may be released. Plate tectonic movements are also associated with volcanism that releases carbon from deep inside Earth's mantle. Today it is estimated by the U.S. Geological Survey that the world's volcanoes release between 180 and 440 million tonnes of carbon dioxide per year - as opposed to the ~35 billion tonnes we release.
Epic carbon releases in the geological past
An extreme carbon-releasing mechanism can occur when magma invades a sedimentary basin containing extensive deposits of fossil fuels. Fortunately, this is an infrequent phenomenon. But it has nevertheless happened at times, including an episode 250 million years ago at the end of the Permian Period. In what is now known as Siberia, a vast volcanic plumbing-system became established, within a large sedimentary basin. Strata spanning hundreds of millions of years filled that basin, including many large coal, oil, gas and salt deposits. The copious rising magma encountered these deposits and quite literally cooked them (fig. 1).
Fig. 1: schematic cross section though just a part of the Siberian Traps Large Igneous Province, showing what science has determined was going on back then, at the end of the Permian Period.
Now laden with a heavy payload of gases, boiled out of the fossil fuel deposits, some of the magma carried on up to the surface to be erupted on a massive scale. The eruptions – volcanism on a scale Mankind has never witnessed - produced lavas that cover an area hundreds of kilometres across. Known as the Siberian Traps, because of the distinctive stepped landforms produced by the multiple flows, it has been calculated that the eruptions produced at least three million cubic kilometres of volcanic products. Just for a moment think of Mount St Helens and its cataclysmic May 1980 eruption, captured on film. How many cubic kilometres with that one? Less than ten.
Recently, geologists working in this part of Siberia have found and documented numerous masses of part-combusted coal entrapped in the lavas (Elkins-Tanton et al. 2020; fig. 2). In the same district are abundant mineral deposits formed in large pipes of shattered rock as the boiling waters and gases were driven upwards by the heat from the magma.
Fig. 2: an end-Permian smoking gun? One of countless masses of part-combusted coal enclosed by basalt of the Siberian Traps. Photo: Scott Simper, courtesy of Lindy Elkins-Tanton.
It has been calculated that as a consequence of the Siberian Traps eruptions, between ten trillion and one hundred trillion tons of carbon dioxide were released to the atmosphere over just a few tens of thousands of years. The estimated CO2 emission-rate ranges between 500 and 5000 billion tonnes per century. Pollution from the Siberian Traps eruptions caused rapid global warming and the greatest mass-extinction in the fossil record (Burgess et al, 2017). There are multiple lines of hard geological evidence to support that statement.
We simply break into those ancient carbon reservoirs via opencast or underground mines and oil/gas wells. Through such infrastructure, the ancient carbon is extracted and burned. At what rate? Our current carbon dioxide emissions are not dissimilar to the estimated range for the Siberian Traps eruptions, at more than 3,000 billion tons per century. The warning could not be more clear. Those telling you the climate's changed before are omitting the critical bit – the details. And when you look at the details, it's not always a pretty sight.
Last updated on 14 February 2023 by John Mason. View Archives
@ 750 MA Rodger
WOW MA Roger what would I do without your knowledge and brilliance?
I immensely thank you for your response!
Here we go! My favorite denier is back to attacking me.
Why don't you tell us about the severe weather up through the 1700s? Oh, that's right, you can't, because nobody recorded it.
I'm guessing you're totally oblivious to the fact that the Romans grew grapes in Britain and made wine. The Emperor Hadrian was drinking and enjoying that wine.
I responded with a NOAA link that stated.
Clues about the past climate are buried in sediments at the bottom of the oceans, locked away in coral reefs, frozen in glaciers and ice caps, and preserved in the rings of trees. Each of these natural recorders provides scientists with information about temperature, precipitation, and more. Many of these have some type of layers, bands, or rings that represent a fixed amount of time, often a year or growing season. The layers vary in thickness, color, chemical composition, and more, which allows scientists to extrapolate information about the climate at the time each layer formed.
[PS] Desparation to be retreading that old one. Try here.
What does wine making in England have to do with anything? The Romans brought it to England, so what? They liked it, and it was unknown there until then. The climate made it possible, although never ideal. It was cultivated in England almost without interruption until the tax laws of the 19th century discouraged production, and later WW1 activity demanded the land. It was cultivated throughout the so-called little ice age as well. What does that show? That England's climate was stable for about 2000 years. Big deal, like we didn't know that.
England's climate today is far more conducive to growing grapes for the wine industry than at any point in recorded history.
I'll post the links tomorrow.
Your denier is clearly desperate and unencumbered by an education in the science in question.
@ [PS] LOL that's a new one on me. I had never heard of it so it must be a desperate attempt by this denier!
@753 Philippe Chantreau
I thought the same thing...what the heck does wine making in England have to do with anything. Glad to be able to expose this denier as he's been commanding the stage for quite some time as if he's some sort of expert! *rolled eyes*
@ 754 Daniel Bailey
Agree his house of cards has been slowly tumbling down since I arrived to "educate" him.
Thanks everyone I've been learning a lot from you all!
Here's those details and links on vineyards then vs now:
While England had 42 vineyards at the time of the Domesday Book, as is well known, there are now over 300 commercial English vineyards today. So the climate today in England is much more conducive to wine-making than during the Roman occupation of England.
http://www.english-wine.com/vineyards.html
Emphasis and underlining added.
https://www.winegb.co.uk/visitors/background-info/history-of-the-industry/
By 1977, there were 124 reasonable-sized vineyards in production – more than at any other time over the previous millennium. The website of the English wine producers suggests that at present extent of vineyards in Britain probably surpasses that of the Medieval Warm Period between circa 900 AD to 1300 AD.
http://www.realclimate.org/index.php/archives/2006/07/medieval-warmth-and-english-wine/
New Scientist Link
https://www.eh-resources.org/historical-climatology/
In case anyone was wondering about Vikings and vineyards:
LINK
@ 756 Daniel Bailey
Thank you!
Is our current Holoceen cooler than previous interglacial periods...thus there is nothing to worry about? A denialist posted this.
From my understanding we should be in a cooling era but as we all know we are in a warming era.
Current peak global temperatures have already exceeded those of the Eemian OR the Holocene, looking at the land station data (red):
http://www.columbia.edu/~mhs119/Temperature/T_moreFigs/
Since the peak temperatures of the Holocene 7,000 years ago, global temperatures naturally cooled 0.8 C.
Over the past 100 years, the warming from human activities has warmed the globe 0.8 C, utterly erasing that natural 7,000-year cooling.
With plenty more warming to come.
Bigger image here.
Thank you so much Daniel Bailey!
A denier is claming these things:
The irrefutable scientific evidence is that Earth is always warmer and wetter, never warmer and drier. That will increase the amount of arable land and also increase food production. That's good news for farmers in foreign States, but not good news for American farmers who will have difficulty competing globally.
The irrefutable scientific evidence also shows that in all 8 recorded Inter-Glacial Periods, the sea levels rose 3 meters to as much as 14 meters, even when CO2 levels were 260 ppm to 280 ppm CO2.
So, whether CO2 levels are 260 ppm or 400 ppm makes no difference, because the sea levels are going to rise 3 meters to 14 meters no matter what happens.
Are these claims accurate?
Also is this accurate?
Antarctica was warmer 1,000 years ago, long before the industrial revolution and before there has been an increase in CO2 attributed to man.
I'll have more to say tomorrow, but as a preliminary answer, you're chasing the dog's tail. Stop.
Demand evidence for their claims, including source citations.
Pretty much every single item you quoted is a baldfaced lie or untruth.
He claims to have irrefutable evidence.
Make him damn well show it.
@ 762; 763 Daniel Bailey
Done!
I look forward to your responses!
Thank you!
Warmer and wetter is true - CC relation requires it. However, the very broad pattern (with lots of regional exceptions) is that the wet get wetter, dry get dryer. There is no guarantee of more arable land where you want it. Does mean he now accepts global warming? More like "I will believe any nonsense that can justify sitting on our hands". More likely latter and as we said before, you are wasting your time.
Warmer in Antarctica 1000 years ago? Umm, let's see that evidence.
And for science - eg observations and models, try here. The Palmer drought index looks at both precipation and evaporation.
However, I doubt your denier will open any evidence that might contradict what they would like to believe. If someone isnt prepared to let data inform their opinion, then it isnt worth arguing.
TVC15 @760/761,
It is a smorgasbord of denialist assertions you present.
☻ The "Antarctic was warmer 1,000 years ago" assertion looks a little difficult to uphold in any way. There are reconstructions from ice core data (for instance Ciais et al (1994) fig 7) which shows Antarctic temperatures over the last 10,000 years waggling about by a maximum of about a degree centigrade. (Note the Ciais et al graphic is sensibly using an 'average-over-the-last-5,000-years' as a datum.) The thermometer record (eg Berkeley Earth) shows recent warming of a similar amount (although there is a lot of variability in the warming depending where you are in Antarctica) so this evidence suggests it was colder in Antarctica 1,000 years ago. The image below is gleened from a posting on the planet Wattsupia and appears to be based on data from Marcott et al (2013). The 1,000 years ago temperature again is shown as being colder.
☻ The interglacial sea level has been discussed before, introduced up-thread @715. It was shown that only two of the last 8 interglacials had higher SLR than today, not all eight. The SLR will mainly depend on how much of Greenland & Antarctica melts out, a process that stopped in this present interglacial 8,000 yers ago, and AGW is the process that is doing that melting today.
☻ The "Earth is always warmer and wetter, never warmer and drier" assertion isn't correct. The missing word word is 'atmosphere' which will be, as scaddenp @765 points out, wetter under the CC relationship. So if we have more wet in the atmosphere, will that translate firstly into more rain always falling on the earth beneath. Globally apparently not. This NOAA graphic shows global temperature and global rainfall are not well aligned. (The graph is from here and is for precipitation over global land)
And secondly, as scaddenp @766 describes, even if rain and temperature were inexorably linked, that warmer atmosphere is demanding to be always wetter than it was when cooler and will thus be sucking more moisture right out of that very same land to re-charge its wetness.
Here's a question I've often thought of related to past climate... In periods of a hothouse Earth, like the cretacious, what would the weather have been like? All we ever see are illustrations of dinosaurs in lush tropical landscapes. There would have been a helluva lot more energy in the climate system and so many more extreme weather events.
I'll address a portion of that, now that scaddenp and MA Rodger already weighed in on the rest.
Again, saying that there is irrefutable evidence pretty much ensures that he's making that claim up. If he had such "irrefutable scientific evidence", he'd have cited it.
Part of the fallacy on display here is the presumption that interglacials are interchangeable and equal. They are not. They are the confluence of orbital factors and the "memory" of the climate over time (climate memory has been demonstrated to extend some 800,000 years or more, depending upon the metric in question). A consilience of studies point out that the best analogue for the modern Holocene Interglacial is MIS (Marine Isotope Stage) 19 (per Giaccio et al 2015, Yin and Berger 2015, Vavrus et al 2018, etc).
Looking at the 5 most recent interglacials, we see that sea levels are not identical (from Grant et al 2014, Figure 2):
From Dutton et al 2015, Figure 1, we see that sea levels from previous interglacials are tightly tied to temperatures...and we know from innumerable studies that global temperatures are tightly intercorrelated with atmospheric carbon dioxide levels:
However, emerging evidence (from Grant 2019) for that Mid-Pliocene sea level on the very right-side of Dutton 15, Figure 1 above is that sea levels associated with an atmospheric composition of carbon dioxide like today saw a contribution of about 20 meters just from the Antarctic Ice Sheet by itself. I believe Rob DeConto is coming out with a similar paper soon on that subject.
Figure 6.10 The Whanganui RSL record on the left with the precession-paced MPWP and obliquity-paced late Pliocene sections highlighted with different GIS, AIS and NHIS configurations and SLE illustrated for interglacial and glacial extreme conditions relative to present-day Antarctica (0 m; central figure). The anti-phased 15 m amplitudes of the MPWP are interpreted as 5 m from GIS offset by ~20 m from AIS present day to peak interglacial. Higher amplitudes would then include larger-than-present AIS (nearing LGM; Clarke and Tarasov, 2014). While the late Pliocene amplitudes include increasing NHIS contributions and smaller interglacial configurations.
To sum for this portion, previous interglacials are as unique as are your fingerprints, but contain similarities constrained by physics, with sea levels of the time correlated with global temperatures and atmospheric carbon dioxide levels.
At present, the human burning of fossil fuels is driving an atmospheric composition and temperature associated with a time when sea levels were over 20 meters higher than at present, imperiling coastal port cities around the world and threatening areas where over 2 billion people currently live.
Thank you, scaddenp, Daniel Bailey and MA Rodger!
I'm with scaddeep's statement: "If someone isnt prepared to let data inform their opinion, then it isnt worth arguing".
I realize how utterly useless my efforts are in trying to help the "deniers" understand the science that supports human caused climate change.
I have learned so much from you all when I post the denier claims. I thoroughly appreciate the responses as you provide me with insights that I would not have been able to discover myself.
However I've grown tired of dealing with the deniers. If they can't understand what they are seeing all over the globe right now as I type this there is no amount of science that will open up their minds.
Here is just another sample of the type of denier minds out there.
i have looked at a lot of evidence from both sides of the argument, and i dont need someone to tell me what my conclusions should be. and there is PLENTY of geological evidence that this round of warming is nothing more than a natural event, one that had been going on for the last 2 million years, ever since the north and south american continents collided. 100,000 years ago the arctic was ice free. and as has been noted many times by many people in many ways, here are a few truths you need to take into account;
1: we are out of the last period of glaciation by only 15,000 years roughly
2: the AGW crowd is complaining about an increase of 1 degree C over 150 years, but there is geological evidence that 15,000 years ago the temperature went up by something more like 10-15 degrees C in TEN years.(i didnt know there are that many SUVs back then, who knew?)
3: we are still ten degrees COOLER than at this same time during the last intergalciation period, and the one before that, and the one before that for the last 2 million years. and its funny how the AGW crowd FAILS to take into account previous interglaciation periods, and what was NATURAL warming.
and if you think that i am just being crazy, then why is the IPCC scientists solution always more regulations and more taxes and redistributing the wealth of the developed nations to those nations that are still developing? and why is it that all the so called climate change protocols penalize the developed nations, mostly western europe and the US, and ignore the rest of the world? why is china given a pass, along with india? two of the highest CO2 emitters in the world?
if the AGW message was more consistent, and required ALL countries to stick to the climate change protocols, then perhaps their message might be more acceptable, and more people might actually listen to them.
in the end these protocols are nothing more than a way for the UN to control the worlds population, and to work to usher in one world government with the UN running things, and no national sovereignty of any kind.
now you claim i am a science denier, but that isnt the truth here. i suppose you also consider the science settled, and that is NEVER the case. the science is NEVER settled, except in the case of the closed minded, non scientific lemmings.
I see no point in spinning my wheels on a mind such this.
TVC15 @770,
Well, let that be a lesson for you!!
Denialism isn't logical. It turns folk into swivel-eyed loons.
To correct his nonsense-
♣ It was 3 million years ago (not 2) that North & South America collided and joined up, a process that did kick off the Arctic glaciation which then resulted in c3 million years of ice ages. And over tha last 1 million years the ice ages were significantly bigger. Presumably the present warming that is bringing this 3-million-year-period to an end can be blamed on the collision of the USSR and the Republic of China with the United States of America, these all constituting significantly large land masses.
♣ You probaly could argue the Arctic was ice-free 100,000 years ago but only through the peak of the summer melt season (as in the Arctic Ocean having the levels of summer ice we would declare today to be ice-free).
♣ 15,000 years ago we were still coming out of the last ice age. We were out nearer 10,000 years ago (as the graphed ice core data clearly shows).
♣ The extreme global temperature changes since the Last Glacial Maximum were nothing like "10-15 degrees C" except at a regional level (ie Greenland). And the period over which these increases occurred (the data graphed shows two large sudden Greenland increases in the last 20,000 years - +12ºC at 14.5kybp & +9ºC at 11.5kypb - which were not 10-year periods of increase but 200-year periods. I don't think the ice cap volumes exist in the northern hemisphere to achieve a repeat performance today.
♣ The relative temperature of different interglacials has been discussed in this thread before and so we know the swivel-eyed loon is having difficulty hearing this particular message. So, yes, we do think he is "just being crazy" and that craziness is why he has such difficulty accepting the science and its implications.
♣ With regard to emisions controls, we can, of course, treat all people on Earth equally as the denialist wishes. The science says that anthropogenic CO2 emissions of more than 700Gt(C) will be bad and with 7.7 billion folk living on the planet, that would be an allowance of 91t(C) per head(historical) ('historical' as your allowance-use is handed down from previous generations).
So let's calculate that allowance using Global Carbon Project figures and present-day population. Note these GCP territorial emission data only go back to 1959. Getting full historical figures would be possible (& correcting for increasing population could be factored in) but the general result will not change. That would mean that China still had an outstanding carbon allowance of 54t(C) per head, India 82t(C)/head while the good old USA has exceded its allowance and so has to pay back 238t(C)/head into the collective kitty. If full historical emissions were included, the US pay-back would be greater still, not qute as great as the UK pay-back if taken to the beginning of the Industrial Revolution. (From 1959 the UK pay-back is a trifling 47t(C)/head). Luxembourg from 1959 has a pay-bacl 0f 199t(C)/head but would be the country facing the biggest carbon-emissions pay-back with full historic figures.
Denial is a sad thing to behold. Denialist folk become happy to dismiss the evidence witout any assessment of what they are ignoring. It is simply done. "The IPCC assessment reports? A complete pack of lies!!"
More telling is the misuse of the remiaining information that you do accept. As you are ignoring whole swathes of actual data, your sources tend to be limited and adjusting the findings beyond that limited evidence becomes a necessity. So some, no all previous ice ages were warmer, golly, 10 degrees warmer, 20, 100 degrees warmer. We should be grateful we live now and not then!!!!
And how does the following rate on the scale of untruthfulness given it comes from a real climatologist, abet a retired one. It's from Lindzen's seminar at the UK House of Commons in 2012. (@ 32.20mins in the first videoed part of his talk linked here. (You-tube link here)
The implication is that we have here a retired climatologist who considers a gobal average temperature increase of less than (0.7 x 20=) 14ºC to be unremarkable. Are we then supposed to take such a retired climatologist as a serious authority on climate?
What perhaps we cannot judge is how much a denier knows he is misrepresenting the data he presents, that he is effectively lying. I suppose gross exageration can be justified because the denialist message is to them the correct message and, and denialists don't have the resources to counter all the lies that you climate alarmists generate with all your fake IPCC science.
For my small contributions, you are most welcome.
If only there were actual sides. Because that would imply that both "sides" were roughly equal.
In the discussions around global warming and its anthropogenic causation, there are those who focus on the science using the scientific method and logic, seeking reproducible evidence that best explains what we can empirically measure. We call them scientists, the real skeptics.
Then there is everyone in the extremely small but vocal minority, those who ignore the above in favor of slander, innuendo, unsupported assertion and character assassination in favor of promulgating false equivalence to support the ephemeral facade of "debate" and "sides".
But it is not about the science, the bulk of the science was settled, decades ago. Deniers posing as skeptics set up a charade tableau of false equivalence to poison the well of public acceptance of that science.
A parsimonious harping at the font of stolen, out-of-context and context-less emails proven not germane to the science is continuing on in the prosecution of the agenda of denial.
Truth, science and reputable journalism all sacrificed to the unholy alter of false equivalence under the guise of promulgating a fallacious "debate".
There is no debate. All that remains is the informed and the uninformed.
Those professing the false equivalence of "both sides" are the journalist in this story.
Moral, dear readers: Don't be that journalist.
The discussion surrounding the science of climate change and its human-causation are a Möbius strip comprised of 170 years of evidence from hundreds of thousands of scientists from virtually every country on the planet. Meaning that from an evidence perspective, only one side exists, because only one side uses evidence.
Even the petroleum extraction companies researched the subject themselves and affirm the unassailable facts, physics and evidence of AGW.
Per the oil companies, which admitted it in court, under oath:
The People of the State of California vs BP PLC et al (page 6, line 6).
About the "2 sides of athe argument" thing: there is really no such thing when considering all the aspects of climate science studied, the weight of the evidence leaves no doubt. I remember a video clip by James Hansen in which he expressed the problem in the simplest possible visualization: imagine a square meter of the Earth, put a little candle on it, close to one watt of output. Seems like a very little thing. Now put one on every square meter of the planet's surface: every square meter of every ocean, every square meter of the Arctic, Antarctic, every square meter of every city, and of every desert, every square meter of the mountains, plains, every single square meter of the surface of our home planet. This is so staggeringly enormous that it defies the imagination. We humans are not well equipped to think about tis kind of thing and prioritize our other silly preoccupations down.
@ 772 Daniel Bailey
For my small contributions, you are most welcome.
Daniel, your contributions have been an enormous help to me...nothing small about them! I am grateful to each person here who responds to the things I post as I've learned so much from all of you!
@ 771 MA Rodgers
Well, let that be a lesson for you!!
Denialism isn't logical. It turns folk into swivel-eyed loons.
I agree! I've come to realize that there is no point in discussing science with people who are anti-science or not literate in science. It's a huge waste of my time! If they are literate in science but want to learn then that's a different scenario and I feel happy helping them understand scientific concepts.
However when scientifically liberate people make false statements about science such as the climate deniers do I feel it's a duty to a certain point to expose their misinterpretations or myth spreading lies.
You guys have helped me to better do that!
Thank you!
Ops I meant when scientifically illiterate people make false staements...