[watsisname]

It has been six years since AR4, and the IPCC's latest Physical Science Basis Report on climate change is now available.  Note this is the final draft, so there are a lot of figures to be added and presumably an aesthetic pass to make it less eye-unfriendly.  It is also over 2200 pages long, so the summary for policy makers is recommended for those who don't want to dive into what is basically a textbook the size of Texas.

Some big points:

-Warming of the climate system is unequivocal, and is evident on land, sea, troposphere, and by ocean heat content. (I add that observed changes in the upper atmosphere are also consistent with this.) There have been many climate changes throughout Earth history, but as far as we know there was never one with the rapidity that we are seeing now. This isn't surprising; atmospheric greenhouse gas concentrations have never changed this rapidly.

-The human influence on current climate change is clear. It is extremely likely that human activity has been the dominant cause of the observed warming since the mid-20th century. (Note: ‘extremely likely’ means 95 to 100% confidence).  This is an increase from the ~90% confidence level in AR4.

-Globally averaged land/ocean surface temperature, calculated by linear trend, shows a warming of 0.65 to 1.06°C, median of 0.85°C, since pre-industrial times.  As far as the goal of keeping temperature rise below 2°C goes, we're almost half way there by temperature, and a lot closer than that by emissions / time-frame.

-Slight change in estimates of climate sensitivity.  The new range is 1.5 to 4.5°C temperature rise for a doubling of CO2, compared to the previous estimate of 2 to 4.5°C, with the most likely value unchanged at 3°C.  This reflects new estimates across the lower range of sensitivity.  Also, the likelihood of values below 1°C and above 6°C have been cut dramatically.  Contrary to some media claims; 1.5°C as the new lower bound should not be reassuring -- it still yields >2°C temperature rise by 2100 across a broad range of emissions scenarios.  This level of warming is unacceptable by international agreement.  The upper limit of 4.5°C for sensitivity is also just as likely as the lower limit, and under the same emissions scenarios would be disastrous for us. 

-Evidence of changes in extreme weather: daily max/min temps, heavy precipitation events, heat waves, etc.  Nothing too surprising here since AR4/SREX.

-Ocean warming accounts for >90% of energy accumulated in the last 3 decades, with 60% being in the top 700 meters.

-It is about as likely as not that rate of heat uptake in oceans was slower in the last decade than the one prior, but it is unlikely that there was any change in the lower layers, where interannual variability is smaller. What this means is that media reports of global warming having slowed down or paused this last decade are not supported by evidence.  What is happening is a slowdown of surface/tropospheric temperature rise as heat is being transferred to the deep ocean, combined with reduced solar luminosity during this deep solar minimum.  Similar slowdowns, and speedups, can be seen in the past, and will continue in the future, and are simple consequences of natural variability.

-Ice sheets globally are losing mass, and it is very likely that the Greenland Ice sheet’s mass loss rate has accelerated. It is likely that the Greenland Ice Sheet will disappear, on a timescale of millenia, if global temperature rises above some threshold between 1 and 4 degrees warmer than pre-industrial levels. What this means is that we may find ourselves being committed to the irreversible loss of Greenland's ice, and the many meters of long term sea level rise that comes with that, if we do not act very soon.

-There is high confidence that climate change is affecting permafrost, leading to increased polar methane emissions. This is quite a nasty feedback effect, as methane is a very efficient greenhouse gas.

-There are many lines of evidence showing substantial Arctic warming since the mid 20th century, in agreement with climate model predictions and the ice-albedo feedback effect.

-Quantification of sea level rise and updated projections for the future.

-Improved climate modelling since AR4, and with greater spatial resolution. (woo!)

-The net climate feedback from all types of clouds is likely positive.  (I thought this was a little surprising).

-Improved understanding of carbon cycle feedbacks.

Much more.

edit:  Huh, I thought I had put a link to the report in this post.  Fixed.

[redsniper]

many meters of long term sea level rise that comes with that, if we do not act very soon.

gg coastal cities
Better move inland.

[Goober5000]

-The human influence on current climate change is clear. It is extremely likely that human activity has been the dominant cause of the observed warming since the mid-20th century. (Note: ‘extremely likely’ means 95 to 100% confidence).  This is an increase from the ~90% confidence level in AR4.

The IPCC is hoping that if they shriek more loudly, more people will pay attention to them.  It isn't working because no matter how you dress something up with fancy academic language and impressive statistics, you can't cover up observable reality.

The global warming charade is already crumbling.  Another decade should suffice to put a stake through the heart of it.

[watsisname]

Observable Reality

I dunno, maybe you don't live on Earth or something.

[Beskargam]

I hope (assume) that was sarcasm?

Been reading some of the watered down versions of this, about to dive into the full version in my physical climatology class. Kinda excited. Yay science. Bad Climate change. On a random note a found it entertaining that I had to ask a chem prof why methane was a much better (as in worse for us) greenhouse gas than say CO2 instead of my Climatology prof. It makes sense, just unexpected

[The E]

The IPCC is hoping that if they shriek more loudly, more people will pay attention to them.  It isn't working because no matter how you dress something up with fancy academic language and impressive statistics, you can't cover up observable reality.

The global warming charade is already crumbling.  Another decade should suffice to put a stake through the heart of it.

Soooo

Do you have actual data to back that up?

Also, "fancy academic language"? Really? That's a reason to dismiss findings now?

[Goober5000]

Soooo

Do you have actual data to back that up?

Also, "fancy academic language"? Really? That's a reason to dismiss findings now?

If there's nothing to back it up, fancy language is just hand-waving.

Read this, for instance:

“I think that the latest IPCC report has truly sunk to level of hilarious incoherence,” Dr. Richard Lindzen told Climate Depot, a global warming skeptic news site. “They are proclaiming increased confidence in their models as the discrepancies between their models and observations increase.”

And...

The I.P.C.C. also glossed over the fact that the Earth has not warmed in the past 15 years, arguing that the heat was absorbed by the ocean.

“Their excuse for the absence of warming over the past 17 years is that the heat is hiding in the deep ocean,” Lindzen added. “However, this is simply an admission that the models fail to simulate the exchanges of heat between the surface layers and the deeper oceans.”

The fact is that the predictive models of the IPCC and other organizations are simply flawed, with their predictions failing, or being retracted, in a spectacularly laughable manner (viz. the claim that the Himalayan glaciers would disappear by 2035).  And there are flaws in the process itself, as revealed by the various Climategate leaked emails.

Feynman is turning over in his grave.

[watsisname]

Goober here seems to be testing the limits of Poe's Law, yet I can't help shake the feeling he is actually being serious...

On a random note a found it entertaining that I had to ask a chem prof why methane was a much better (as in worse for us) greenhouse gas than say CO2 instead of my Climatology prof. It makes sense, just unexpected

I've been curious about that yet never looked it up -- I mean I know greenhouse gases tend to be molecules with dipole moments, such that they have vibrational modes that correspond to infrared wavelengths, but why one molecule is so much better at absorbing/transmitting than another is unknown to me.  What'd your professor say?

[Luis Dias]

Ahah I think this thread is gonna be hilarious. I am slightly inclined to agree with Goober, although I'm not going all the way with the same rethorical tone. I do think the IPCC is in some pains to explain why we are simultaneously even more sure than in 2007 that we know what is the case when in fact all the models have almost failed miserably to produce the slowdown of the past 20 years in warming. Any Bayesian-like minded folk would be "huh?" on that one.

My favorite blog post so far on this work has been, however, Judith Curry's:

My original intention for this thread was to go through and try to map the IPCC’s logical argument.  I quickly got dizzy owing to seemingly unwarranted assumptions and incomplete information (such as: did the climate models use the correct external forcing for the first decade of the 21st century, or not?).  I was then going to illustrate how any reasonable propagation of uncertainty of individual assertions/arguments through their main argument would produce much lower confidence in their overall conclusions.  For example, they seem to have eliminated high CO2 sensitivity as a problem.   Not to mention high confidence in increasing trend following 2012 (this high confidence comes right after blowing the prediction of the previous decade).  And of course not to mention the relevant journal articles that didn’t get mentioned.

Apart from these obvious flaws, reading that text and trying to follow it is positively painful.  Can someone remind me again how and why all this is supposed to be useful?

http://judithcurry.com/2013/09/30/ipccs-pause-logic/

Go read it, it has a direct quote from the IPCC on the "pause". It's amazingly long and inhumanly written! It's as if they don't want no one on their right mind to read it and actually understand it.

[Luis Dias]

Goober here seems to be testing the limits of Poe's Law, yet I can't help shake the feeling he is actually being serious...

On a random note a found it entertaining that I had to ask a chem prof why methane was a much better (as in worse for us) greenhouse gas than say CO2 instead of my Climatology prof. It makes sense, just unexpected

I've been curious about that yet never looked it up -- I mean I know greenhouse gases tend to be molecules with dipole moments, such that they have vibrational modes that correspond to infrared wavelengths, but why one molecule is so much better at absorbing/transmitting than another is unknown to me.  What'd your professor say?

Nevermind that the methane "problem" isn't a problem whatsoever and that methane levels aren't going anywhere. The IPCC itself doesn't regard it as a big issue as well. (But I guess being against the mainstream is only "bad" if you do it in one predetermined direction!)

I must also congratulate the IPCC for getting the science right in what comes to the issues of extreme weather events and the non-observed link between them and global warming. They were already right in 2012 in their interim report on the subject matter and they continue to do so, despite all the rantings of activists and pseudo-scientific bloggers who still make these silly proclamations today.

[Nuke]

i dont really care. if we get another good summer like this last summer keep ****ing up the environment. its an improvement for me.

[watsisname]

My original intention for this thread was to go through and try to map the IPCC’s logical argument.  I quickly got dizzy owing to seemingly unwarranted assumptions and incomplete information (such as: did the climate models use the correct external forcing for the first decade of the 21st century, or not?).  I was then going to illustrate how any reasonable propagation of uncertainty of individual assertions/arguments through their main argument would produce much lower confidence in their overall conclusions.  For example, they seem to have eliminated high CO2 sensitivity as a problem.   Not to mention high confidence in increasing trend following 2012 (this high confidence comes right after blowing the prediction of the previous decade).  And of course not to mention the relevant journal articles that didn’t get mentioned.

Apart from these obvious flaws, reading that text and trying to follow it is positively painful.  Can someone remind me again how and why all this is supposed to be useful?

http://judithcurry.com/2013/09/30/ipccs-pause-logic/

Go read it, it has a direct quote from the IPCC on the "pause". It's amazingly long and inhumanly written! It's as if they don't want no one on their right mind to read it and actually understand it.

Sounds like Ms. Curry is really struggling to comprehend it.  I haven't a clue why; it's really quite simple:
-Large volcanic eruptions provide a negative forcing.  There have not been many large eruptions lately, so this is not an important factor to the 'pause'.
-Solar luminosity has been lower than average during this deep solar minimum -- this is a negative forcing.
-Internal variability accounts for much of the rest -- decadal cycles of heat transfer between the atmosphere and oceans.
-Put it all together, we find that global warming has not paused, just as I said in the OP.  Such slow-downs, and speedups, are an expected phenomenon.  You can see them in the past and they most assuredly will continue in the future, with the underlying trend being that of ongoing warming for as long as radiative forcing continues to be enhanced.

A blog commenter also pointed out this passage:

“However, it is very likely that the climate system, including the ocean below 700 m depth, has continued to accumulate energy over the period 1998–2010 (Section 3.2.4, Box 3.1). Consistent with this energy accumulation, global-mean sea level has continued to rise during 1998–2012, at a rate only slightly and insignificantly lower than during 1993–2012 (Section 3.7). The consistency between observed heat-content and sea-level changes yields high confidence in the assessment of continued ocean energy accumulation, which is in turn consistent with the positive radiative imbalance of the climate system (Section 8.5.1; Section 13.3, Box 13.1).

Bad Astronomer Phil Plait has an excellent commentary on this as well.

Nevermind that the methane "problem" isn't a problem whatsoever and that methane levels aren't going anywhere. The IPCC itself doesn't regard it as a big issue as well. (But I guess being against the mainstream is only "bad" if you do it in one predetermined direction!)

Thankfully, rising sea levels are actually helping to stabilize oceanic methane clathrates despite the warmer temperatures, but high latitude and shallow sea methane sources are at risk and expected to be an ongoing source of enhanced radiative forcing, as the IPCC report discusses, particularly in section 12.5.5.5.  The actual concentration of methane is also not the only metric of its global warming potential, as it has very important disequilibrium chemistry associated with it which has other effects on climate.  See 8.2.3.3 for more information.

[Beskargam]

Aw, ****. I had a big long post explaining it and my mobile browser ate it. Le sigh. Will redo it later

[IronBeer]

I don't doubt that there is a potential for anthropogenic climate change. Hell, I'd be willing to concede that it even is most likely the case.

However, I do have to take a slight issue with the general methods employed by the study (I have not read the study directly, but I have gone over a summary on Ars Technica).
Claiming to have data on temperature variance over the whole surface of the earth dating back to 1901 is a very bold claim, and one that I am instinctively inclined to doubt. Climate data from most land areas? Sure, I can believe that. But claiming knowledge of temperature variance in ocean areas is something I find very hard to accept, especially if this supposed data reaches back over a century.

I could go on with some other procedural issues I have with a lot of "high-visibility" climate studies, but I think I'd betray my relative ignorance in the field. To be clear, I don't patently doubt the underlying thesis of climate change. Rather, I am skeptical of some specific claims and I feel that highly rigorous data collection (grid of temperature stations across the whole earth's surface f.ex) would make me personally a lot more comfortable with the claims.

[watsisname]

We obviously do not have a complete global grid of temperature measurements before the satellite era.  So a lot of work has to be done to produce a global temperature dataset, involving the use of the instrumental data that we do have, plus a wide range of proxies.  From this we can reconstruct global temperatures from now to thousands and even hundreds of thousands of years ago, and these reconstructions are remarkably reliable.  The thermal history of the oceans can also be determined through a range of methods. 

Also note that the IPCC is not performing original research; they are reporting a synthesis of all available climate studies.  You may think of it as being like a huge literature review, the most extensive of any scientific field.

[Luis Dias]

Phil Plait hasn't had any good commentary on the climate discussion for years now. He's a rabid blogger with pals such as Michael Mann and John Cook as his primary sources. Anyone who quotes Sceptical Science as a source isn't credible in my book (and I would think everyone would agree by now, ever since their debacle over the 97% idiotic study and the Lewandoski affair, etc.)

And yes, I'd say that those paragraphs are indeed terribly written and if one is a bit cynic one would even say it's designed to be that way. I was obviously exagerating, it is possible to read them. The conclusion that the system hasn't stopped warming is inane, and it merely encompasses the very ad hoc method of changing one's parameters and metrics to get the foregone conclusion one begins with. They went on looking for the missing heat everywhere and alas they found it. Statistics are awesome like that.

I also noticed that the usual GW deniers' arguments of "climate variability", "PDO" and so on are now embebbed within the IPCC analysis as reasons for why the warming paused. Not even a hint that the warming of the nineties might have been caused by a symmetric variation, nor a recognition that perhaps this argument isn't as inane as we've been told icessantly through the years as "denier myths" and so on. It only seems to work one direction.

The written sentence that was required of the scientists to take out for political reasons, the one that mentioned that the reasons for the pause were more or less unknown is the real truth that is missing here. It's also missing some good papers from last year (and this one) that mention one of the biggest hypothesis for the current pause: a slower sensitivity than was previously thought.

[watsisname]

Phil Plait hasn't had any good commentary on the climate discussion for years now. He's a rabid blogger with pals such as Michael Mann and John Cook as his primary sources. Anyone who quotes Sceptical Science as a source isn't credible in my book (and I would think everyone would agree by now, ever since their debacle over the 97% idiotic study and the Lewandoski affair, etc.)

I see you pathologically dismissing any information that doesn't conform with your world-view, Luis, and not providing much in the way of a refutation of the material I have posted which is based on evidence and links to journal articles.

[Luis Dias]

I do read Phil's blog posts, and they are always about whamming the deniers' most derpish comments, instead of providing an actual informed and nuanced discussion over these matters, which are I think, quite important to be debated in the whimsical polarized and idiotic manner that Phil is all too happy to provide. He lives in a world where science is being fought by rabid GOPers and fundamentalist christians, either by creationist ideas or anti-vaxxers or moon hoax believers and because of this "experience" he really reads like someone who thinks his usual DEBUNK! EXPOSE! DENOUNCE! hammer works on every problem.

It does not, and the climate is the one issue where his discussing methods really fail spectacularly.

[watsisname]

Your dislike of Phil Plait's blogs is noted, but you still haven't tackled the argument, let alone provide evidence or sources to back yourself up.

Come on, Luis, you're an intelligent individual with an obvious scientific orientation.  We're looking at global warming, and noting that over 90% of the thermal energy added to the system ends up in the oceans.  So if the claim is that global warming has slowed down, paused, or whatever you call it, is true, then why is the ocean's heat content still increasing, with the associated ongoing thermal expansion?  What is wrong with the physical explanations for the differences in radiative flux and energy transfer between the different earth systems?  Why does an examination of global temperature, when accounting for these factors, yield the continued and unabated signal expected under standard global warming theory?  What is the cause of the other decelerations and accelerations observed in the last century of global temperature?

[Beskargam]

Take 2, this time with laptop.
@ Scotty:
So It sounds like you have a solid grasp of science so I can explain this well I believe. I apologize if this comes off as lecturing or goes over what you already know, both are tendencies I have when explaining things. I will be using Methane and Carbon Dioxide for this explanation.

Structure
First keep in mind the geometric structure of each of these molecules. CO2 is linear due to having two double bonds, and CH4 is tetrahedral. (diagram 1 on attached pic illustrates the structures both as bond line drawings and in their correct 3D orientation). It is important to keep in mind that in CO2 the pi bonds restrict rotation around the axis as well as making the bond shorter and stronger.

Vibration States
We draw molecules as unmoving, but in reality the bonds constantly move. Vibration states occur as a result of this natural proccess. (diagram 2 shows how vibration states work for carbon dioxide). They stretch and bounce around. In order for energy to be absorbed the molecule must have a dipole (I'm not 100% sure why this is yet, but as a wild guess, I would say that having a dipole means concentrated electrons and exciting the area with light has a higher chance of hitting all/most of the electrons). Neither CH4 or CO2 have natural dipoles, but as seen on diagram 2, the last two vibration states do have dipoles. The first occurs due to "asymmetrical stretching" and the second by "bending". The number of vibration states is given by 3N-6, where N is the number of atoms. This only holds true in the case of molecules that do not have double bonds, they are modeled by 3N-5. So CO2 has 4 vibration states, and CH4 has 9 (To lazy to draw that many). As the number of vibration states increases, so do the number of dipoles. Each molecule and their dipoles can be excited only by a certain quanta of energy. This energy is modeled by lamda = (hv)/E. lamda is wavelength, h is planck's constant, v is frequency, and E is energy. The more vibration states exist, the more wavelengths can be absorbed (larger absorption spectrum). Same equation applies to emission. Note absorbed radiation is longwave. There is one more factor:

Concentration
As you know the concentration of CO2 is higher than that of CH4. The wavelengths that CO2 absorbs at are already "cluttered" with CO2 so to speak, at least in comparison to CH4. Increasing the concentration ([CO2]) has little impact (comparatively) on positive radiative forcing because some of the light at that wavelength is already taken in by existing CO2. Basically there is less light to excite CO2. This actually works on a log scale, you have to exponentially increase the concentration of CO2 in order to get continuously increasing positive radiative forcing (It should be noted this is what humanity is doing). On the other hand you have a lower concentration of CH4, and therefore more light is available for absorption by it. The end result is that slight increases in CH4 has a large impact on forcing. Additionally, CH4 stays in the atmosphere longer than CO2.


@Luis
And that is why CH4 is a problem. Both CO2 and CH4 are important and need to be controlled. A little bit of CH4 goes a long way. Additionally there is quite a lot of methane trapped in sinks all over the world (particularly in the northern latitudes) that (According to everything we know now) will release as a secondary feedback mechanism as a result of climate change.


I will add some more details and particularly numbers later tonight


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