The "Pause" - A Review of Its Significance and Importance to Climate Science 77

[rconnor]

----------Introduction---------
A comparison of recent temperature trends in isolation of earlier data, say 1998-present, to long(er)-term temperature trends, say 1970-present, reveals that more recent temperature trends are lower than long-term temperature trends. This has led many, including many prominent climate scientists, to refer to the recent period as a “pause”, “hiatus” or “slowdown”. While in isolation of any other context besides two temperature trends, the term “pause” or “hiatus” may be quasi-accurate, much more context is required to determine whether these terms are statistically and, more importantly, physically accurate.

It should be noted that most times when these terms are used by climate scientists, they keep the quotation marks to indicate the mention-form of the word and are not implying an actual physical pause or hiatus in climate change. The subsequent research into the physical mechanism behind the “pause” has continually demonstrated that it is not indicative of a pause in climate change nor does it suggest a drastic reduction in our estimates of climate sensitivity. However, this fact appears to be lost on many who see the “pause” as some kind of death-blow to the anthropogenic climate change theory or to the relevancy of climate change models.

While this subject has been discussed repeatedly in these forums, it has never been the focus but rather used as a jet-pack style argument to change the conversation from the subject at hand to the “pause” (“Well that can’t be right because the Earth hasn’t warmed in X years!”). Revisiting past threads, I cannot find an example of where someone attempted to defend the “pause” as a valid argument against anthropogenic climate change. It is brought up, debunked and then not defended (and then gets brought up again 5 posts later). The hope is to discuss the scientific literature surrounding the “pause” to help readers understand why the “pause” is simply not a valid argument. While some points have been discussed (usually by me) before, this post does contain new research as well as 2014 and 2015 temperature data, which shed even more light on the topic. The post will be split into three parts: 1) the introduction (and a brief discussion on satellite versus surface station temperature data sets), 2) Does the “pause” suggest that climate change is not due to anthropogenic CO2? and 3) Does the “pause” suggest that climate models are deeply flawed?

------Why I Will Be Using Ground-Based Temperature Data Sets-------
Prior to going into the meat of the discussion, I feel it necessary to discuss why I will be using ground-based temperature data sets and not satellite data sets. Perhaps one of the most hypocritical and confused (or purposefully misleading) arguments on many “skeptic” blogs is the disdain for all ground-based temperature data sets and the promotion of satellite temperature data sets. The main contention with ground-based temperature data sets is that they do not include raw data and require homogenization techniques to produce their end result. While I am not here (in this thread) to discuss the validity of such techniques, it is crucial to understand that satellite temperature data sets go through a much more involved and complex set of calculations, adjustments and homogenizations to get from their raw data to their end product. Both what they measure and where they measure it are very important and highlights the deep confusion (or purposeful misdirection) of “skeptic” arguments that ground-based temperatures are rubbish and satellite-based temperatures are “better”.

[ul][li]Satellites measure radiances in different wavelength bands, not temperature. These measurements are mathematically inverted to obtain indirect inferences of temperature (Uddstrom 1988). Satellite data is closer to paleoclimate temperature reconstructions than modern ground-based temperature data in this way.[/li]
[li]Satellite record is constructed from a series of satellites, meaning the data is not fully homogeneous (Christy et al, 1998). Various homogenization techniques are required to create the record. (RSS information)[/li]
[li]Satellites have to infer the temperature at various altitudes by attempting to mathematically remove the influence of other layers and other interference (RSS information). This is a very difficult thing to do and the methods have gone through multiple challenges and revisions. (Mears and Wentz 2005, Mears et al 2011, Fu et al 2004)[/li]
[li]Satellites do not measure surface temperatures. The closest to “surface” temperatures they get are TLT which is an loose combination of the atmosphere centered roughly around 5 km. It is also not even a direct measurement channel (which themselves are not measuring temperature directly) but a mathematically adjustment of other channels. Furthermore, due to the amount of adjustments involved, TLT has constantly required revisions to correct errors and biases (Christy et al 1998, Fu et al 2005).[/li]
[li]See the discussion on Satellite data sets in IPCC Report (section 3.4.1.2)[/li]
[li]Satellite data and the large amount of homogenization and adjustments required to turn the raw data into useful temperature data are still being question to this day. Unlike ground-based adjustments which lead to trivial changes in trends (from the infamous Karl et al 2015), recent research shows that corrections of perhaps 30% are required for satellite data (Weng et al 2013 .[/li][/ul]

None of this is meant to say the satellite temperature data is “wrong” but it very clearly highlights the deep-set confusion in the “skeptic” camp about temperature data sets. If one finds themselves dismissing ground-based temperature data sets because they require homogenization or adjustments while claiming satellite temperature data sets are superior have simply been lead astray by “skeptics” or are trying to lead others astray. Furthermore, it clearly demonstrates that any attempt to compare satellite data (which measures the troposphere) to the surface temperature output of models is completely misguided (*cough*John Christy *cough*). It is for these reasons that I will use ground-based data in the rest of the post.

Again, I would like to state that I do not wish this to be a focal point of this discussion. I am merely outline why I will be using ground-based temperature data sets and my justification for that as, undoubtedly, someone would claim I should be using satellite temperature datasets. In fact, I appear to be in pretty good company; Carl Mears, one of the chief researchers of RSS (and the same Mears from all the papers above), stated:

My particular dataset (RSS tropospheric temperatures from MSU/AMSU satellites) show less warming than would be expected when compared to the surface temperatures. All datasets contain errors. In this case, I would trust the surface data a little more because the difference between the long term trends in the various surface datasets (NOAA, NASA GISS, HADCRUT, Berkeley etc) are closer to each other than the long term trends from the different satellite datasets. This suggests that the satellite datasets contain more “structural uncertainty” than the surface dataset

If this is a topic of interest to people, perhaps starting your own thread would be advisable as I will not be responding to comments on temperature data sets on this thread. Now, onto the actual discussion…

 

[Panther140]

I don't think syngas would be a 100% replacement for all of our fuels. I also don't think its wise to make a substantial amount of syngas and then rely on one single source. There is a lot of carbon-based waste that we currently make.

By the way, only 29% of the world is covered by land. Only a portion of that facilitates substantial growth year round, and the plants are only exposed to sunlight for a portion of those days..

You are the one who is most concerned with this alleged problem in the first place. I would think you would also be on the forefront of the solution, which I hope you don't believe to be lithium batteries and coal electricity!

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

 

[cranky108]

" the US uses 51% of its land area for agriculture already."

I believe you misunderstood what they said. I believe they mean that 51% of developed land is used for agriculture.

A great deal of land can't be used for agriculture because of a lack of water. And of that 51% a good deal of it is used as pasture, which really isen't that much used.

I object to misquoting facts to prove a point.

Another issue is ethanol has proved to reduce smog in many cities, or we could go back to MTBF if you would like. The point here is the two news perspectives are both wrong.
Ethanol does make the air cleaner, even if it requires more fuel to produce it than it provides.

 

[GregLocock]

MTBF= mean time between failures? Where are these studies, ethanol is cleaner than /what/ so far as smog goes? Smog is zapped by catalysts, I doubt they care overmuch whether the engine is supplied with partially burnt hydrocarbons (ethanol) or unburnt hydrocarbons (gasoline). Are you seriously claiming that ethanol burning cars are significantly cleaner than gasoline burning cars of the same recent vintage? I'd hazard a guess that most smog these days is not from new gasoline or ethanol cars at all.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[rconnor]

As I’ve said before, why discuss solutions with people that reject the problem in the first place? We did, however, have a brief discussion on it in this thread (see 30 Nov 15 18:23). (Interestingly followed by a conversation on “it’s changed before”…oh how the cycle of whack-a-mole spins)

I'll entertain the opposition for a minute and help you reach a non-destructive non-intrusive solution to your alleged problem.

A rather good diversion away from your previous argument on why “it’s not us”. Given that you don’t know the date of the MWP, when it’s suppose to be central to your argument, it might be a smart strategy.

 

[Compositepro]

I believe Cranky was referring to MTBE (methyl tert-butyl ether) which is an oygenated additive for gasoline that was required by the EPA to reduce smog, but is now banned because it was soluble enough in water to cause ground water contamination problems

 

[IRstuff]

OK, my bad, percentage is only 18%, of which, only a small fraction is available for ethanol-related corn. But, that doesn't matter, because we'd need to grow hundreds of times more biomass to create sufficient syngas to replace our current oil consumption. So, unless we use less than 0.1% of arable land to grow anything at all, we don't have sufficient land area to make that work.

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //

http://www.engineering.com/AskForum/aff/32.aspx

faq731-376 forum1529

 

[Panther140]

IRstuff, its important to know that I said it wouldn't be a 100% replacement. You are also operating under the assumption that we would use traditional farming techniques and traditionally farmed plants in traditional locations.

Think in the gray area a little more.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

 

[IRstuff]

How is a factor of even, say, 100 anywhere in a "gray" area? To blithely say that just by thinking in a "gray" area we can get factors of 10 or 100 is just not realistic plan of action. Might as well say, "Miracle needed here." Why not think in the "gray" area for a 95% efficient solar cell? That would be a once every 20 year investment instead of a continual energy, fertilizer, and water consumption for biomass.


And even my original number was only for oil, which did not include coal, which is 800 million short tons.

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //

http://www.engineering.com/AskForum/aff/32.aspx

faq731-376 forum1529

 

[Panther140]

IRstuff, the point I was making is that we shouldn't be fixated on a single source to replace all of our energy sources.

Syngas is an attainable way to recycle carbon emissions, provide wildlife environment, and clean the air without wildly changing the fundamentals of our industry. That is what it does. The level of practicality decreases with scale. That is true for all forms of energy, which is why we don't rely on one single form of energy.

Solar panels have their place, but why put a solar panel in any environment where it prevents plant life?

There needs to be a matrix of sources that can be used optimally.




"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

 

[IRstuff]

I was not actually suggesting solar, because the actual efficiency is so poor. My point was that while it's easy to say, "think outside the box," getting a useful answer is extremely difficult, which is why the box is there in the first place. 95% efficient solar cells are essentially unobtainium, just like 100x improvement in crop yield, which would be the only way to get syngas and other alternatives of that type into a tolerably competitive price point.

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //

http://www.engineering.com/AskForum/aff/32.aspx

faq731-376 forum1529

 

[rb1957]

think fusion nuke

another day in paradise, or is paradise one day closer ?

 

[rconnor]

I do not see how a scientifically literate person would conclude that our recent climate trends are unnatural.

Panther140, this was an extremely strong statement you made (as were many others you made).

You’ve provided no evidence to support the statement (besides a paper from Michael Mann, the poster boy for the antithetical position, and even that had nothing to do with your point). You’ve asserted that orbital cycles show that “it’s natural” when, in reality, orbital cycles are (1) already a requisite part of the CO2 theory, (2) demonstrate that CO2 sensitivity is high, (3) moreover, cannot be explained without high CO2 sensitivity and (4) cannot explain the current warming (neither the timing nor the rate). You’ve failed to demonstrate a scientific understanding of paleoclimatology (not knowing the date of the MWP certainly didn’t help with that). You’ve failed to describe how “it’s changed before” if CO2 sensitivity is low. You’ve certainly failed to support the quote above. In fact, our discussion begs the exact opposite question - how could one conclude that our recent climate trends are natural?

Now you appear to be slinking away from this position without addressing anything substantive. While this is certainly common in this discussion, I’d like to hold you to your original statement. As I’m bowing out of this topic, I want to make sure we conclude the conversation on “it’s changed before”. I don’t expect it to completely end it as an argument against mitigation (despite the fact it’s actually a strong argument for mitigation) but hopefully this can be used as a reference.

So, again, I’ll repeat the original exercise – please provide a physical explanation of geological, paleo and present temperature variances if the planet is not sensitive to atmospheric CO2 concentrations. This certainly does not rest all on Panther140’s shoulders. Numerous posters (ex. GregLocock, zdas04, orenrynorsk) have played the “it’s changed before” card, none have stuck around to defend it. I’ll address any defenses of this position and then drift away from this conversation entirely.

 

[rconnor]

I’ll add that the criticism that “[I’m taking] the absence of other causes…as validation of [my] hypothesis” is untrue. It is the evidence that supports the CO2 theory that provides me with confidence that it is true. However, as I’m trying to highlight in the exercise, it is also the strength of the CO2 theory that makes counter-theories fail so quickly.

The explanatory power of the CO2 theory for geological, paleo and present temperature variances is incredibly strong. It starts from 19th century physics, confirmed by laboratory experiments, that the greenhouse effect increases temperatures by ~1 to 1.4 K per doubling of CO2 (here or here). This, alone, cannot explain the extent of past changes. Incorporating feedback effects, such as albedo changes, CH4 release (both of which are evident in past changes) and water vapour increase (which can be demonstrated by laboratory experiments), along with negative feedbacks such as Planck feedback and lapse rate, you get a sensitivity of ~2.2 K to 4.8 K (source). This sensitivity range is required to, and does an excellent job at, explaining past and present climate change.

As CO2 sensitivity is largely dependent on positive feedbacks, if you want to say “sensitivity is low” then you are really saying “feedbacks are likely negligible or negative”. This becomes very difficult as albedo and water vapour feedbacks are pretty solid. This further supports the current CO2 theory and makes counter-theories that much more unlikely, as they cannot utilize the same feedbacks as CO2.

Take, for example, the claim that “orbital cycles are responsible for climate change and CO2 has no (or negligible) impact”. Paleoclimateology indicates that the first part is true; orbital cycles, indeed, appear to coincide with past climate changes. However, orbital cycles also coincide with large releases of CO2 (during warming periods) and reductions (during cooling periods) of CO2. This claim assumes that this is a negligible factor, in contrast to the current understanding which states that while CO2 didn’t initiate the warming, it was responsible for the majority of the extent of the warming. So, ignoring the impact of CO2 but given the same temperature rise, we’d need to put more weight on the impact of albedo, CH4 and water vapour feedbacks of the insolation changes. However, as these feedbacks are the same as CO2 feedbacks, we’ve inadvertently demonstrated that CO2 sensitivity is, in fact, high. Thus, we’ve proved the opposite of our original claim. (Note: we needn’t even mention that orbital cycles cannot explain the timing nor the rate of current warming)

Cloud feedback has perhaps the largest uncertainty. Present observations indicate that it is likely small but positive (Clement et al 2009, Lauer et al 2010, Dessler 2010 and Sherwood et al 2014). Furthermore, if asserting a strong negative cloud feedback, then that person needs to explain how this feedback did not dampen past climate changes. Again, “it’s changed before” works against the claim “sensitivity is low”.

Furthermore, “it’s changed before” demonstrates that past climate changes (which were orders of magnitude slower than present changes) had an significant impact on the biosphere and topology of the planet. Past warming periods are linked with most of the major mass extinction events in Earth’s history (Jourdan et al 2014, Burgess et al 2014). So “it’s changed before” works against the claim “it won’t be bad” and “sensitivity is low”. Frankly, the fact that many do not understand that these are mutually exclusive arguments is telling.

So it’s not just that the explanatory power of the CO2 theory is so strong but also that counter-theories fail miserably at providing anything close to the explanatory power of the CO2 theory. In fact, most counter-theories (such as orbital cycles) end up supporting the CO2 theory rather than dismissing it. Thus, the fact “it’s changed before” (a bizarrely common “skeptic” argument) is perhaps the best evidence in support of mitigation measures and the strongest evidence against the “skeptic” position.

But it’s not just the agreement with Paleoclimate that add strengths to the CO2 theory and heaps more leg-work onto counter-theories. Many more recent observations align with predictions of CO2 warming. Here are a few:
[ul][li]Less heat exiting the atmosphere along wavelengths associated with CO2 – correct – solar activity would have no effect on this[/li]
[li]Increased downward infrared radiation along wavelengths associated with CO2 – correct – solar activity cannot explain why it would increase under specific wavelengths[/li]
[li]Nights warming faster than the day – correct – if it was solar activity, the opposite would be true[/li]
[li]Cooling stratosphere, Warming surface – correct – if it was solar activity, both would be warming[/li]
[li]Rising tropopause – correct – solar activity would not affect this[/li]
[li]Cooling and contracting ionosphere – correct – solar activity would have the opposite effect[/li]
[li]Temperatures warming in agreement with climate models – correct, correct, correct (see Part 2 at 7 Oct 15 22:02 for more details) – for reference to solar activity, see Feulner & Rahmstorf 2010 for the impact if (magically) we were stuck in a Grand Solar Minimum from now until 2100. (Hint: it’s very small)[/li]
[li]Rising ocean heat content – correct (and how!) – The very rapid, very consistent rise in OHC dispels the argument that “ocean cycles are causing the warming”. Ocean cycles move heat around the system but they could not both cause a rise in atmospheric temperatures and a rise in OHC; that would violate the conservation of energy.[/li]
[li](The “skeptic’s” favourite) Tropospheric Hot Spots – weak, but growing, evidence (and here). As indicated in a 2006 report, which John Christy was a lead author, “It is likely that a net spurious cooling corrupts the area-averaged adjusted radiosonde data in the tropical troposphere, causing these data to indicate less warming than has actually occurred there”. The two recent papers (Po-Chedley et al 2014 and Sherwood and Nishant 2015) seem to further validate this statement. – Solar activity would also lead to hotspots, so if they were missing (and it looks increasingly like they are not) then that wouldn’t help the “it’s solar” argument either. It should also be added that tropospheric hotspots are an indication of the lapse rate feedback, a negative feedback. So missing tropospheric hotspots would work against the “climate sensitivity is low” argument. But worry not, the more data that comes in the more hotspots appear to be there.[/li][/ul]

What this list demonstrates is that the CO2 theory is, indeed, testable (and falsifiable). It makes predictions, we compare those predictions against observations, the predictions agree with observations. Outside of building a 2nd Earth, with all the interactive effects of ocean-atmospheric dynamics, ocean currents, prevailing wind patterns, etc., and the ability to speed up and isolate interacts, this is the best way to test the theory. This has been referred to as a “ragbag” list of observations and that I’ve “cherry-picked” predictions that were correct and “ignored” predictions that were incorrect. My question would be, what have I left out? Certainly nothing central to the CO2 theory. Furthermore, given the strong consilience of multiple, independent lines of evidence “skeptics” cannot simply cherry-pick one aspect (let’s say hotspots, even though, as stated above, that argument is slowly dying), ignore all other aspects (such as the rest of the list) and proclaim the theory dead. The strength of the theory requires a very strong, very robust argument to kill it. Not only have I not see a very strong, very robust argument against the theory, I haven’t seen a kinda-strong, remotely valid argument. Where accurate, “skeptic” arguments are very weak (such as “there’s still uncertainty”) and where strong, “skeptic” arguments are inaccurate (such as “sensitivity is low”).

[Edit: Added list of observations to further emphasize the consilience of the CO2 theory. Feel free to use this as a fairly good (but certainly not complete) overview on why the CO2 theory is so strong.

 

[Panther140]

"Take, for example, the claim that “orbital cycles are responsible for climate change and CO2 has no (or negligible) impact”. Paleoclimateology indicates that the first part is true; orbital cycles, indeed, appear to coincide with past climate changes. However, orbital cycles also coincide with large releases of CO2 (during warming periods) and reductions (during cooling periods) of CO2."

I have actually linked CO2 and temperature together quite clearly.

I don't have the patience or the crayons to explain this causal relationship to you today. This should help get you started.

http://www.chem4kids.com/files/react_catalyst.html

 

[rconnor]

The only place I see that you’ve “linked CO2 and temperature together quite clearly” is by saying “it’s orbital cycles”. I agree, indeed orbital cycles demonstrates that CO2 drives temperature. But I’m guessing this isn’t what you are getting at.

I patiently await your nobel-prize worthy revolution to atmospheric chemistry and/or radiative physics. Make sure to enlighten me on how this Kuhnian level scientific revolution is consistent with paleoclimate and present climate change.

(and note I’ve added some more information to my last post. However, given your tendency to pick one line to comment on, and ignore the rest, it likely won’t impact your response much)

 

[JNieman]

@Panther140-

Crop-dependent processes do NOT yield wildlife environments. They are fueled by monocrop landscape that is contrary to actual natural wildlife environments. Think about the wildlife you (don't) see in a corn field. Even lumber tree farming shows that the animal culture is drastically different than wildlife as the 'food chains' are not really supported as they are wild. You can't provide a habitat for some animals and expect them to stay if their prey do not like that habitat. Monocrop harvesting is typically dependent upon reliable, predictable, and consistent patterns so that machinery can specialize to it for increased efficiency which makes the process affordable.

Syngas, to be affordable, will not be dependent upon laborious and inefficient harvesting of whatever biomass they encounter. To be affordable, like all crop-dependent processes, farmers will play to the market and plant the fastest growing, highest yield, biomass they can, in a monocrop environment, just like soy beans, corn, etc. Whether it's rapeseed, hemp, bamboo, whatever - it will be a monocrop environment hostile to natural life.

Wildlife does not benefit from syngas.

 

[Panther140]

rconnor -" I agree, indeed orbital cycles demonstrates that CO2 drives temperature. But I’m guessing this isn’t what you are getting at."

Is that a serious statement? Please explain the causal relationship between atmospheric CO2 levels and distance from the sun.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

 

[rconnor]

You really don't read what's said to you, do you.

I directed you to previous posts about Milankovitch/orbital cycles on 3 Feb 16 22:32:

Well, I’m at at it, Panther140,
Re: “it’s changed before” – See 27 Oct 15 18:27, 28 Oct 15 22:03.

You ignored that and responded:

Are you familiar with the orbital mechanics of the earth relative to the sun and other planets?

Which was odd, considering that I just directed you to past discussion on Milankovitch cycles. I replied with:

Yes, I am. In fact, I discussed Milankovitch cycles in both of the posts that I directed you to read. Please see 27 Oct 15 18:27 and 28 Oct 15 22:03. For a much more detailed review of Milankovitch cycles, see here at 22 Apr 15 21:28.

Milankovitch/orbital cycles require large carbon feedbacks to drive the majority of the extent of interglacial warming. So if your mechanism is orbital cycles, you're agreeing with the current scientific understanding and with high CO2 sensitivity. If CO2 sensitivity is low, there’s no way to explain the extent of the change in temperatures. So, you’re doing a better job proving my point than yours.

I also, in my reply to zdas04, discussed Milankovitch cycles and explained how assuming CO2 sensitivity is negligible leads to the conclusion that CO2 sensitivity must actually be high (No CO2 impact = higher positive feedbacks. Since they are the same feedbacks for CO2, CO2 sensitivity is still high).

You ignored both of these. I noted this to you at 6 Feb 16 18:09.

I then re-explained Milankovitch cycles to you at 11 Feb 16 03:21. You seem to have read the first sentence but didn't get much further.

Maybe you'd prefer to watch a video, rather than read. Heck, we all learn in different ways. In which case, see these three videos by Richard Alley - one, two or three

While we're at it, here's a list of other stuff you've ignored:
- You didn't know the date of the MWP (despite it being central to your "it's changed before" argument.
- You didn't indicate what paleoclimate data set you use to base your assertions on (especially after you were critical of the coverage of most data sets, using anything other than PAGES 2K, which has the best coverage, would be hypocritical).
- You didn't comment on the fact that orbital cycles cannot explain the timing nor rate of the current warming.
- You have not addressed the fact that past changes in climate:

1) coincide with changes in CO2​

2) require high CO2 sensitive to explain them​

3) have been orders of magnitude slower than present climate change​

4) have resulted in drastic changes to the biosphere (mass extinctions) and topology of the planet​

 

[Panther140]

I did explain why CO2 coincides with temp. I even posted a link to how catalysts work to help explain it to you. CO2 is not causing the warming. The warming is causing CO2 increases.

I did acknowledge pages 2k. The very article that I was linked to even said that the temp was this high before the mini ice age.



"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

 

[rconnor]

The warming is causing CO2 increases.

Oh boy. The atmospheric CO2 increase is anthropogenic, not natural. While there is just piles upon piles of evidence to support this (nice compilation here), perhaps the simplest explanation is the basic mass balance example (which I already linked to you). "CO2 increase is natural" is one of those arguments (along with "sky dragon slayers") that is simply dismissed in any serious circle (heck, even most "skeptic" circles).

But, humour me, what's causing the warming? Magic? It ain't orbital cycles. The timing doesn't line up, the next phase of the cycle would be cooling (not warming) and the rate of warming is far too fast. Is the released CO2 a positive feedback (or do you reject basic radiative physics as well)? If so, why wouldn't anthropogenic CO2 also be a positive forcing in the first place?

I did acknowledge PAGES 2K. The very article that I was linked to even said that the temp was this high before the mini ice age.

PAGES 2K does not support your position, at all. The MWP was cooler than the current period and wasn't even present globally, despite your (unsupported) claims otherwise. PAGES 2K says that 1971-2000 temperatures were warmer than any period in nearly 1400 years. If we included 21st century temperatures, it becomes even more anomalous. The rate of global warming is completely unseen in the reconstruction. And, for the Nth time, natural forcing cannot explain it, in fact they are moving in the opposite direction. Any way you want to slice it, the recent warming ain't natural. As PAGES 2K says in the FAQ (also previously linked to you):

The global warming that occurred in the 20th century reversed a long-term global cooling trend. This pre-industrial cooling trend was likely caused by natural factors that continued to operate through the 20th century, making the 20th century warming more difficult to explain without the likely impact of increased greenhouse gasses.

This is contrary to what you've been saying and supports what I've been saying.

To add, you could have just looked at the very first graph I showed to you. Note the last green dot, this represents the last 30 year period (1971-2000) analyzed in the PAGES 2K conclusion. Note the red line showing observational data. Note how the red line is above all the other green dots. Note how rapidly the red line rises. Now, note how incompatible this is with your position.

Add to that the following:
Zeebe et al 2015

the present anthropogenic carbon release rate is unprecedented during the Cenozoic (past 66 million years) by at least an order of magnitude… Furthermore, future ecosystem disruptions will likely exceed the relatively limited extinctions observed during climate aberrations throughout the Cenozoic.

And for those that want to argue “it’s changed before” and “it won’t be bad” see Bond and Wignall 2014, Jourdan et al 2014, Burgess et al 2014, Clark et al 2016, etc.

The fact “it’s changed before” makes four things very clear:
[ul 1][li]The Earth is sensitive to atmospheric CO2 concentrations[/li]
[li]Current climate change is not explainable by natural mechanisms[/li]
[li]That past climate changes, despite being orders of magnitude slower than the current change, were extremely disruptive to the biosphere, leading to large extinction events.[/li]
[li]”Skeptics” that use “it’s changed before” as an argument against mitigation measures have no idea what they are talking about.[/li][/ul]