IPCC Report is Released

[skierinvermont]

The fact that the IPCC now indicates that there is substantial disagreement among sensitivity estimates.. enough to not issue a most likely estimate is huge. As you put it.. that's the climate debate in a nutshell.

 

There always was substantial disagreement with the range being 2-4.5C and quite a few studies suggesting it was possibly even higher than 4.5C. 

 

Frankly, I find the IPCC statement a bit puzzling. The range of uncertainty found in published papers has broadened slightly from 2-4.5C to now 1.5-4.5C. I assume that is the 95% confidence interval. What prevents them from issuing a 70% confidence interval of 2.5-3.5C? Or 2-4C, or whatever it may be. A 70% confidence interval would be useful information for formulating policy.

 

If you have 5 different papers, using 5 different methods yielding ECSs of:

 

1.5-2.5

2-3

2.5-3.5

2.5-4.5

3-4.5

 

Then despite the lack of agreement, the multiple lines of evidence overlap most in the 2-4C range, and I would think you could still call this the "best estimate" or "70% confidence interval." I don't really understand what prevented them from doing this.

 

Perhaps they explain a little better in the contents of the report.

[blizzard1024]

With all due respect, if you're discrediting the entire peer review process, on what can you base any theory or opinion?

I was talking about climate science in particular. There are fields, like meteorology for example, where you can have disagreements

with the consensus if you have data/math/theory to back it up and still get published. It is much harder in climate science

if you go against the consensus. Since climatology deals with the atmosphere I don't understand how anyone can be so

certain that a trace gas that is a weak GHG is the control knob for the Earth's temperature. The atmosphere is so complex

with many non-linear feedbacks etc. But climate science has grown from a minor less well known scientific field to a major field

because of alarmism. So in order to continue the funding stream there has to be a problem. If climate sensitivity is small

then the funding dries up. The objectivity is gone IMO. again these are my opinions which I am entitled too. There is

plenty of research that shows that CO2 is a minor player in the climate system that don't get published in the main stream

climate journals for the very reason I stated originally. Look at what Partridge et al 2009 had to go through!!! 

[blizzard1024]

There always was substantial disagreement with the range being 2-4.5C and quite a few studies suggesting it was possibly even higher than 4.5C. 

 

Frankly, I find the IPCC statement a bit puzzling. The range of uncertainty found in published papers has broadened slightly from 2-4.5C to now 1.5-4.5C. I assume that is the 95% confidence interval. What prevents them from issuing a 70% confidence interval of 2.5-3.5C? Or 2-4C, or whatever it may be. A 70% confidence interval would be useful information for formulating policy.

 

If you have 5 different papers, using 5 different methods yielding ECSs of:

 

1.5-2.5

2-3

2.5-3.5

2.5-4.5

3-4.5

 

Then despite the lack of agreement, the multiple lines of evidence overlap most in the 2-4C range, and I would think you could still call this the "best estimate" or "70% confidence interval." I don't really understand what prevented them from doing this.

 

Perhaps they explain a little better in the contents of the report.

Even if the ECS is high (~4C), how long will it take for the equilibrium temperature to be reached? that is the bigger question. Since the oceans are apparently taking up most of the heat it could be centuries for it to show up in the global mean surface temperature. This gives mankind a lot of time. Also what is the mechanism that the deep water of the oceans are getting all this heat? Plus how do we know that the oceans are not recovering from the LIA? It takes a long time for the oceans to equilibriate given their shear mass. The oceans basically damp all climate change forcings. 

[Snow_Miser]

If you have 5 different papers, using 5 different methods yielding ECSs of:

 

1.5-2.5

2-3

2.5-3.5

2.5-4.5

3-4.5

 

Then despite the lack of agreement, the multiple lines of evidence overlap most in the 2-4C range, and I would think you could still call this the "best estimate" or "70% confidence interval." I don't really understand what prevented them from doing this.

 

We've seen multiple papers give a most likely value below 2 Degrees C for the ECS without any error margins. With the Otto et al. paper finding the ECS to be 2.0 Degrees C, instead of 3.0 Degrees C, and the TCR to be much lower, that was also huge, especially considering there were many IPCC scientists whom co-authored the paper. The trend, as Tacoman has said, has been for lower sensitivities, and hence why the IPCC also expanded their range from 2-4.5 Degrees C to 1.5-4.5 Degrees C.

[Snow_Miser]

Even if the ECS is high (~4C), how long will it take for the equilibrium temperature to be reached? that is the bigger question. Since the oceans are apparently taking up most of the heat it could be centuries for it to show up in the global mean surface temperature. This gives mankind a lot of time. Also what is the mechanism that the deep water of the oceans are getting all this heat? Plus how do we know that the oceans are not recovering from the LIA? It takes a long time for the oceans to equilibriate given their shear mass. The oceans basically damp all climate change forcings. 

 

This is a good point. Even if sensitivity is high, it may take centuries before equilibrium is finally met.

 

http://www.springerlink.com/content/w5484721301160ut/

 

From the link:

 

"If climate sensitivity in fact proves to be high, these considerations prevent the high temperatures in the fat tail from being reached for many centuries."

[Snow_Miser]

Abstract

The small but stubbornly unyielding possibility of a very large long-term response of global temperature to increases in atmospheric carbon dioxide can be termed the fat tail of high climate sensitivity. Recent economic analyses suggest that the fat tail should dominate a rational policy strategy if the damages associated with such high temperatures are large enough. The conclusions of such analyses, however, depend on how economic growth, temperature changes, and climate damages unfold and interact over time. In this paper we focus on the role of two robust physical properties of the climate system: the enormous thermal inertia of the ocean, and the long timescales associated with high climate sensitivity. Economic models that include a climate component, and particularly those that focus on the tails of the probability distributions, should properly represent the physics of this slow response to high climate sensitivity, including the correlated uncertainty between present forcing and climate sensitivity, and the global energetics of the present climate state. If climate sensitivity in fact proves to be high, these considerations prevent the high temperatures in the fat tail from being reached for many centuries. A failure to include these factors risks distorting the resulting economic analyses. For example, we conclude that fat-tail considerations will not strongly influence economic analyses when these analyses follow the common—albeit controversial—practices of assigning large damages only to outcomes with very high temperature changes and of assuming a significant baseline level of economic growth.

 

It's not out of context.

[Jonger]

1. his correct surname is Paltridge.

2. the paper had problems after publication because of serious problems with its methodology. citing a debunked and discredited paper really has no place in this conversation.

3. your entire viewpoint is a parroting back of his non-scientific book where he essentially asserts that there is a conspiracy to keep AGW research alive even though it's not a big deal.

these attack on peer review have no place in a forum which is dealing with science. I'd like to see them curtailed. I'd also like to see more substantive discussion of the points in the IPCC report on the part of those who deny them.

 

http://grammar.ccc.commnet.edu/grammar/capitals.htm

 

We understand you work in peer review. Your opinion is obviously compromised.

[PhillipS]

http://grammar.ccc.commnet.edu/grammar/capitals.htm

 

We understand you work in peer review. Your opinion is obviously compromised better informed.

 

 There, I fixed it for you.

[Snow_Miser]

Surprised no one has posted this yet. All of the chapters are available for access now.

 

http://wattsupwiththat.com/2013/09/30/ipcc-ar5-full-final-report-released-full-access-here/

[blizzard1024]

1. his correct surname is Paltridge.

2. the paper had problems after publication because of serious problems with its methodology. citing a debunked and discredited paper really has no place in this conversation.

3. your entire viewpoint is a parroting back of his non-scientific book where he essentially asserts that there is a conspiracy to keep AGW research alive even though it's not a big deal.

these attack on peer review have no place in a forum which is dealing with science. I'd like to see them curtailed. I'd also like to see more substantive discussion of the points in the IPCC report on the part of those who deny them.

 

1) Yeah...Ok  Paltridge. Sorry.  2) This paper shows drying in the upper troposphere which is counter to the climate consensus.  Therefore it can't be true. It is interesting that the low-level mixing ratios (or specific humidity) up to 850 mb  has shown increases which makes sense with slightly warmer temperatures and evaporation from the Earth's surface. Then... above the convective mixed layer, the moisture gradually decreases in time... especially with height. This suggests that there is compensating drying (increasing precipitation efficiency). This is quite a coincidence. The reanalysis data is often used to show warming which is does but when it shows something that is counter to the consensus it is thrown out. Just like the cloud fraction from the early 1980s to the late 2000s. It correlates well with the observed UAH and RSS temperature trends. This suggests cloud cover regulates climate to some extent. But wait...that data is no good either because it is not related to CO2. 

 

Plus the OHC. How do we know that the OHC has not been on an upswing since the LIA? In addition, the OHC at the deepest layers has gone up hence reducing climate sensitivity significantly. Does the IPCC report indicate what dynamical processes causes this? In fact, IR downwelling does not heat oceans below a couple mm, it heats the land masses. So increasing CO2 only can heat oceans indirectly. It is sunlight in the UV portion of the spectrum that heats down deeper into the oceans. So tell me how CO2 warms the oceans? and by what process does it heat the deep oceans. And if heats the deep oceans how long will it take for the heating to show up in the atmosphere? decades? centuries? Paleoclimate data suggests it would be centuries. The science is settled as you say so you and the IPCC should have all the answers. Please provide them. I am all ears. 

 

3) Oh yeah, I am not into conspiracies either nor did I even know that  Paltridge wrote a book.. IMO the science is far from settled. The atmosphere and climate system are much more complex than even climate scientists are willing to admit.  Meteorologists have a much better understanding of the complexities of the atmosphere because we forecast the weather every day and we see the outcomes. Climate forecasts are for 50-100 years from now. Most if not everyone will never get to see if they are right or wrong.

[skierinvermont]

Of course OHC has been rising since the LIA. Why? Because the earth's radiative properties have been out of equilibrium since the LIA. This can also be deduced from the fact that the earth has been warming since the LIA.

 

However, the idea that OHC would rise to the point that it has risen just because the LIA ended is incorrect. This suggestion reveals a fundamental lack of understanding for why OHC rises.

 

OHC rises because the earth is energetically out of balance. The subsequent warming helps to return the planet to equilibrium. If the factors that caused the LIA had simply "ended" then what you would witness is a very large energy imbalance, rapidly rising OHC and temperature, and a gradual return to equilibrium with both OHC and temperature increase gradually slowing to a halt. 

 

Of course the LIA didn't quite just "end" in a matter of a year. Over the course of several decades (1890-1930) solar forcing went from extreme low values to extreme high values and the high volcanic activity of the late 19th century did not repeat itself. Over this period there was an energy imbalance, as indicated by rising OHC. Thus, temperatures rose and equilibrium was gradually returned. At the same time you also had CO2 beginning to contribute to an energy imbalance. But aerosol emissions by the 50s and 60s pretty much allowed surface warming to catch up and bring the earth fairly close to equilibrium. Only a new source of forcing could have knocked the earth out of equilibrium. This forcing was the accelerating rise in CO2 (which was stronger than the slowing increase in aerosols). 

 

In short, OHC increase is a measurement of the earth's energy imbalance. If the rise in OHC was due to the end of the LIA, we would have witnessed very rapid initial OHC increase (and surface temperature increase) which would gradually decelerate. Instead what we witnessed was some initial rapid warming (due to hot sun, low volcanoes, and a little CO2), a pause as equilibrium was reached (no change in sun or volcanoes, CO2 and aerosols offset each other), and then a renewed acceleration (due primarily to CO2).

[skierinvermont]

I think you have a difficult time comprehending these concepts blizzard because you do not take the diligence, concentration, or patience to thoroughly understand them. 

 

All I see in your posts are splurging out one misunderstanding after another. Like you think you know everything but in reality you've picked up little misunderstandings from around the internet and have a difficult time piecing them together in your head.

[tacoman25]

Of course OHC has been rising since the LIA. Why? Because the earth's radiative properties have been out of equilibrium since the LIA. This can also be deduced from the fact that the earth has been warming since the LIA.

 

However, the idea that OHC would rise to the point that it has risen just because the LIA ended is incorrect. This suggestion reveals a fundamental lack of understanding for why OHC rises.

 

OHC rises because the earth is energetically out of balance. The subsequent warming helps to return the planet to equilibrium. If the factors that caused the LIA had simply "ended" then what you would witness is a very large energy imbalance, rapidly rising OHC and temperature, and a gradual return to equilibrium with both OHC and temperature increase gradually slowing to a halt. 

 

Of course the LIA didn't quite just "end" in a matter of a year. Over the course of several decades (1890-1930) solar forcing went from extreme low values to extreme high values and the high volcanic activity of the late 19th century did not repeat itself. Over this period there was an energy imbalance, as indicated by rising OHC. Thus, temperatures rose and equilibrium was gradually returned. At the same time you also had CO2 beginning to contribute to an energy imbalance. But aerosol emissions by the 50s and 60s pretty much allowed surface warming to catch up and bring the earth fairly close to equilibrium. Only a new source of forcing could have knocked the earth out of equilibrium. This forcing was the accelerating rise in CO2 (which was stronger than the slowing increase in aerosols). 

 

In short, OHC increase is a measurement of the earth's energy imbalance. If the rise in OHC was due to the end of the LIA, we would have witnessed very rapid initial OHC increase (and surface temperature increase) which would gradually decelerate. Instead what we witnessed was some initial rapid warming (due to hot sun, low volcanoes, and a little CO2), a pause as equilibrium was reached (no change in sun or volcanoes, CO2 and aerosols offset each other), and then a renewed acceleration (due primarily to CO2).

 

Which happened to coincide perfectly with a PDO phase flip...

[skierinvermont]

Tell me blizzard, what happens when hot air passes over water? 

 

It warms!!!

 

What happens when cold air passes over the same body of water?

 

It cools!!!

 

 

Now do you think global warming will cause more warm air or cold air? So do you think the oceans will warm or cool?

 

 

You're just getting lost in abstractions that you don't really understand but are eager to utilize in a way that disproves AGW. Perhaps the more practical exercise above will demonstrate why global warming warms the oceans.

[skierinvermont]

Which happened to coincide perfectly with a PDO phase flip...

 

It's possible the ENSO modulation by the PDO (or vice versa) had some warming effect when it flipped, and some cooling effect when it flipped back negative. But the PDO went neutral in 1998 and has been negative since 2008 but this has not coincided with cooling. The effect of the PDO thus cannot be especially strong, and cannot come close to explaining the majority of the increase in temperature since 1975. CO2 on the other hand, is a strong greenhouse gas, and can explain the rise both empirically and theoretically.

 

The PDO also cannot explain why the earth went into a significant and growing energy imbalance in the 1970s which continues to this day.

[Jonger]

Tell me blizzard, what happens when hot air passes over water? 

 

It warms!!!

 

What happens when cold air passes over the same body of water?

 

It cools!!!

 

 

Now do you think global warming will cause more warm air or cold air?

 

That same warm air used to warm the land surface, it hasn't in 15 years.

 

Why did it once warm the land, but not warm the land now?

[skierinvermont]

That same warm air used to warm the land surface, it hasn't in 15 years.

 

Why did it once warm the land, but not warm the land now?

 

What warm air? The air hasn't warmed much in the last 15 years. If there's not an increase in warm air, there won't be warming of the land (by which I presume you mean the land surface?)

[tacoman25]

It's possible the ENSO modulation by the PDO (or vice versa) had some warming effect when it flipped, and some cooling effect when it flipped back negative. But the PDO went neutral in 1998 and has been negative since 2008 but this has not coincided with cooling. The effect of the PDO thus cannot be especially strong, and cannot come close to explaining the majority of the increase in temperature since 1975. CO2 on the other hand, is a strong greenhouse gas, and can explain the rise both empirically and theoretically.

 

The PDO also cannot explain why the earth went into a significant and growing energy imbalance in the 1970s which continues to this day.

 

The PDO remained relatively positive in relation to ENSO until the mid 2000s. 2002-04 was a strongly +PDO period. Even with major -ENSO 1999-2001, the -PDO did not approach the numbers we've seen much of 2008-present.

 

+PDO phase during mid 1920s to mid 1940s....strong global warming trend.

 

PDO flips to negative mid/late 1940s...warming trend halts abruptly....and doesn't begin again in earnest until the late 1970s, right after the PDO flips phases again.

 

Strong global warming trend until early/mid 2000s....right as the -PDO phase begins to take hold again.

 

I don't disagree that energy imbalances exist, or that aerosols have played a role. But your narrative completely ignored the clear and obvious correlations between global temp trends and large-scale oceanic oscillations. 

[blizzard1024]

Of course OHC has been rising since the LIA. Why? Because the earth's radiative properties have been out of equilibrium since the LIA. This can also be deduced from the fact that the earth has been warming since the LIA.

 

However, the idea that OHC would rise to the point that it has risen just because the LIA ended is incorrect. This suggestion reveals a fundamental lack of understanding for why OHC rises.

 

OHC rises because the earth is energetically out of balance. The subsequent warming helps to return the planet to equilibrium. If the factors that caused the LIA had simply "ended" then what you would witness is a very large energy imbalance, rapidly rising OHC and temperature, and a gradual return to equilibrium with both OHC and temperature increase gradually slowing to a halt. 

 

Of course the LIA didn't quite just "end" in a matter of a year. Over the course of several decades (1890-1930) solar forcing went from extreme low values to extreme high values and the high volcanic activity of the late 19th century did not repeat itself. Over this period there was an energy imbalance, as indicated by rising OHC. Thus, temperatures rose and equilibrium was gradually returned. At the same time you also had CO2 beginning to contribute to an energy imbalance. But aerosol emissions by the 50s and 60s pretty much allowed surface warming to catch up and bring the earth fairly close to equilibrium. Only a new source of forcing could have knocked the earth out of equilibrium. This forcing was the accelerating rise in CO2 (which was stronger than the slowing increase in aerosols). 

 

In short, OHC increase is a measurement of the earth's energy imbalance. If the rise in OHC was due to the end of the LIA, we would have witnessed very rapid initial OHC increase (and surface temperature increase) which would gradually decelerate. Instead what we witnessed was some initial rapid warming (due to hot sun, low volcanoes, and a little CO2), a pause as equilibrium was reached (no change in sun or volcanoes, CO2 and aerosols offset each other), and then a renewed acceleration (due primarily to CO2).

How do you know the LIA ended between 1890 and 1930 exactly? If so, it took 1-2 centuries to go into it then why not a century or two to come out of it?? How do you know how quickly the OHC changes in response?  Aerosols in the 50s and 60s?? That is a convenient excuse for the mid 20th century cooling. I have read this before. How about the cold PDO and AMO? Both PDO and AMO cycles can explain pretty much all of the variations in the Earth's temperatures in the last 100 to 150 years. CO2 does have a small influence. But you need feedbacks to make it matter and the paleo data to quantify this is suspect IMO (yes I have read these papers thoroughly). This is because boundary conditions change in times: oceans, H20/clouds the main GHGs, extent of land and glacier, precipitation between during ice ages and interglacials. You don't need CO2 for any of this. CO2 passively follows the temperature trends in the ice core data. That was my epiphany years ago in all this plus CO2 is only a minor GHG. It will cause some small warming but all the feedbacks, clouds etc are not known enough in the real atmosphere. They are "known" in the climate models to some extent but of course these are models and are likely oversensitive based on the observations. Maybe we do equilibriate at 4C(assuming all positive feeback which is highly unlikely IMO)...but that could occur in centuries from the slow ocean heat uptake. Nobody knows the processes or time scales of changing OHC. There is a LOT of water with very high specific heat capacity.   

[blizzard1024]

I think you have a difficult time comprehending these concepts blizzard because you do not take the diligence, concentration, or patience to thoroughly understand them. 

 

All I see in your posts are splurging out one misunderstanding after another. Like you think you know everything but in reality you've picked up little misunderstandings from around the internet and have a difficult time piecing them together in your head.

 I am trying to view this from an objective scientific side like others like Lindzen, Gray, Spencer, Ball, Christy, Curry and others. Of course these folks are morons too I guess according to you. Why do you have to resort to insults too?   My questions were not answered from before. You just attack and try to discredit me. You are very wrong about the way I approach science. I have published refereed papers before in major journals. I also have reviewed many papers and there is a lot that gets through that is total junk (not by my doing!). I know of several PHDs that basically have given up atmospheric science research because they have to tie everything into AGW to get funding which they know is bogus. So I do have a lot of knowledge and experience in this field even though I am a "MET". Fortunately I don't do research in it or rely on it for a living!!!  

[blizzard1024]

The PDO remained relatively positive in relation to ENSO until the mid 2000s. 2002-04 was a strongly +PDO period. Even with major -ENSO 1999-2001, the -PDO did not approach the numbers we've seen much of 2008-present.

 

+PDO phase during mid 1920s to mid 1940s....strong global warming trend.

 

PDO flips to negative mid/late 1940s...warming trend halts abruptly....and doesn't begin again in earnest until the late 1970s, right after the PDO flips phases again.

 

Strong global warming trend until early/mid 2000s....right as the -PDO phase begins to take hold again.

 

I don't disagree that energy imbalances exist, or that aerosols have played a role. But your narrative completely ignored the clear and obvious correlations between global temp trends and large-scale oceanic oscillations. 

amen brother. 

[skierinvermont]

The PDO remained relatively positive in relation to ENSO until the mid 2000s. 2002-04 was a strongly +PDO period. Even with major -ENSO 1999-2001, the -PDO did not approach the numbers we've seen much of 2008-present.

 

+PDO phase during mid 1920s to mid 1940s....strong global warming trend.

 

PDO flips to negative mid/late 1940s...warming trend halts abruptly....and doesn't begin again in earnest until the late 1970s, right after the PDO flips phases again.

 

Strong global warming trend until early/mid 2000s....right as the -PDO phase begins to take hold again.

 

I don't disagree that energy imbalances exist, or that aerosols have played a role. But your narrative completely ignored the clear and obvious correlations between global temp trends and large-scale oceanic oscillations. 

 

Oh so the +PDO from 1977 to 1983 wasn't really a +PDO because we were in El Nino most of that time?

 

The whole point of the PDO is its relationship to causing/reinforcing/feedback loop with ENSO. 

 

We've been over this before.. just because global temperatures stopped warming when the PDO went negative and started when it went positive.. and then kept rising the second time it went negative... doesn't mean that the PDO was a strong causative factor. Much of the eyeball appearance of correlation is simply due to the fact that +PDOs start with Ninos and -PDOs start with La Ninas so obviously you're going to see sharp changes in temperature whenever the PDO flips (mostly due to ENSO). 

 

Statistically the correlation is nowhere close to being strong enough to suggest causation. Theoretically, causation is already well explained by CO2 and aerosols. There's some wiggle room for some effect of the PDO/ENSO in there but there's not a whole ton of evidence for anything more than a small effect (mostly indirect and short-term through ENSO modulation). 

[ORH_wxman]

The full report tries to address the climate models majorly failing in recent years:

 

Box 9.2: Climate Models and the Hiatus in Global-Mean Surface Warming of the Past 15 Years

The observed global-mean surface temperature (GMST) has shown a much smaller increasing linear trend over the past 15 years than over the past 30 to 60 years (Section 2.4.3, Figure 2.20, Table 2.7; Figure 9.8; Box 9.2 Box 9.2 Figure 1a,c). Depending on the observational data set, the GMST trend over 1998–2012 is estimated to be around one-third to one-half of the trend over 1951–2012 (Section 2.4.3, Table 2.7; Box 9.2 Figure 1a,c). For example, in HadCRUT4 the trend is 0.04 ºC per decade over 1998–2012, compared to 0.11 ºC per decade over 1951–2012. The reduction in observed GMST trend is most marked in Northern- Hemisphere winter (Section 2.4.3, (Cohen et al., 2012)). Even with this “hiatus” in GMST trend, the decade of the 2000s has been the warmest in the instrumental record of GMST (Section 2.4.3, Figure 2.19).

Nevertheless, the occurrence of the hiatus in GMST trend during the past 15 years raises the two related questions of what has caused it and whether climate models are able to reproduce it. Figure 9.8 demonstrates that 15-year-long hiatus periods are common in both the observed and CMIP5 historical GMST time series (see also Section 2.4.3, Figure 2.20; (Easterling and Wehner, 2009), (Liebmann et al., 2010)). However, an analysis of the full suite of CMIP5 historical simulations (augmented for the period 2006–2012 by RCP4.5 simulations, Section 9.3.2) reveals that 111 out of 114 realisations show a GMST trend over 1998–2012 that is higher than the entire HadCRUT4 trend ensemble (Box 9.2 Figure 1a; CMIP5 ensemble-mean trend is 0.21 ºC per decade). This difference between simulated and observed trends could be caused by some combination of (a) internal climate variability, ( missing or incorrect radiative forcing, and © model response error. These potential sources of the difference, which are not mutually exclusive, are assessed below, as is the cause of the observed GMST trend hiatus.

(a) Internal Climate Variability

Hiatus periods of 10–15 years can arise as a manifestation of internal decadal climate variability, which sometimes enhances and sometimes counteracts the long-term externally forced trend. Internal variability thus diminishes the relevance of trends over periods as short as 10–15 years for long-term climate change (Box 2.2, Section 2.4.3).

Furthermore, the timing of internal decadal climate variability is not expected to be matched by the CMIP5 historical simulations, owing to the predictability horizon of atmost 10–20 years (Section 11.2.2; CMIP5 historical simulations are typically started around nominally 1850 from a control run). However, climate models exhibit individual decades of GMST trend hiatus even during a prolonged phase of energy uptake of the climate system (e.g., Figure 9.8, (Easterling and Wehner, 2009; Knight et al., 2009)), in which case the energy budget would be balanced by increasing subsurface-ocean heat uptake (Meehl et al., 2011; Guemas et al., 2013; Meehl et al., 2013a).

Owing to sampling limitations, it is uncertain whether an increase in the rate of subsurface-ocean heat uptake occurred during the past 15 years (Section 3.2.4). However, it is very likely2 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). By contrast, there is limited evidence that the hiatus in GMST trend has been accompanied by a slower rate of increase in ocean heat content over the depth range 0–700 m, when comparing the period 2003–2010 against 1971–2010. There is low agreement on this slowdown, since three of five analyses show a slowdown in the rate of increase while the other two show the increase continuing unabated (Section 3.2.3, Figure 3.2).

During the 15-year period beginning in 1998, the ensemble of HadCRUT4 GMST trends lies below almost all model-simulated trends (Box 9.2 Figure 1a), whereas during the 15-year period ending in 1998, it lies above 93 out of 114 modelled trends ((Box 9.2 Figure 1b; HadCRUT4 ensemble-mean trend 0.26°C per decade, CMIP5 ensemble-mean trend 0.16°C per decade). Over the 62-year period 1951– 2012, observed and CMIP5 ensemble-mean trend agree to within 0.02 ºC per decade (Box 9.2 Figure 1c; CMIP5 ensemble-mean trend 0.13°C per decade). There is hence very high confidence that the CMIP5 models show long-term GMST trends consistent with observations, despite the disagreement over the most recent 15-year period. Due to internal climate variability, in any given 15-year period the observed GMST trend sometimes lies near one end of a model ensemble (Box 9.2, Figure 1a,b; (Easterling and Wehner, 2009)), an effect that is pronounced in Box 9.2, Figure 1a,b since GMST was influenced by a very strong El Niño event in 1998.

Unlike the CMIP5 historical simulations referred to above, some CMIP5 predictions were initialized from the observed climate state during the late 1990s and the early 21st century (Section 11.1, Box 11.1; Section 11.2). There is medium evidence that these initialised predictions show a GMST lower by about 0.05–0.1 ºC compared to the historical (uninitialised) simulations and maintain this lower GMST during the first few years of the simulation (Section 11.2.3.4, Figure 11.3 top left; (Doblas-Reyes et al., 2013; Guemas et al., 2013)). In some initialised models this lower GMST occurs in part because they correctly simulate a shift, around 2000, from a positive to a negative phase of the Interdecadal Pacific Oscillation (IPO, Box 2.5; e.g., (Meehl and Teng, 2012; Meehl et al., 2013a)). However, the improvement of this phasing of the IPO through initialisation is not universal across the CMIP5 predictions (cf. Section 11.2.3.4). Moreover, while part of the GMST reduction through initialisation indeed results from initialising at the correct phase of internal variability, another part may result from correcting a model bias that was caused by incorrect past forcing or incorrect model response to past forcing, especially in the ocean. The relative magnitudes of these effects are at present unknown (Meehl and Teng, 2012); moreover, the quality of a forecasting system cannot be evaluated from a single prediction (here, a ten year prediction within the period 1998–2012; Section 11.2.3). Overall, there is medium confidence that initialisation leads to simulations of GMST during 1998–2012 that are more consistent with the observed trend hiatus than are the uninitialised CMIP5 historical simulations, and that the hiatus is in part a consequence of internal variability that is predictable on the multiyear timescale.

( Radiative Forcing

On decadal to interdecadal timescales and under continually increasing effective radiative forcing (ERF), the forced component of the GMST trend responds to the ERF trend relatively rapidly and almost linearly (medium confidence, e.g., (Gregory and Forster, 2008; Held et al., 2010; Forster et al., 2013)). The expected forced-response GMST trend is related to the ERF trend by a factor that has been estimated for the 1% per year CO2 increases in the CMIP5 ensemble as 2.0 ± 0.7 W m–2 °C–1 (90% uncertainty range; (Forster et al., 2013)). Hence, an ERF trend can be approximately converted to a forced-response GMST trend, permitting an assessment of how much of the change in the GMST trends shown in Box 9.2 Figure 1 is due to a change in ERF trend.

The AR5 best-estimate ERF trend over 1998–2011 is 0.23 ± 0.11 W m–2 per decade (90% uncertainty range), which is substantially lower than the trend over 1984–1998 (0.34 ± 0.10 W m–2 per decade; note that there was a strong volcanic eruption in 1982) and the trend over 1951–2011 (0.30 ± 0.10 W m–2 per decade; Box 9.2, Figure 1d–f; numbers based on Section 8.5.2, Figure 8.18; the end year 2011 is chosen because data availability is more limited than for GMST). The resulting forced-response GMST trend would approximately be 0.13 [0.06 to 0.31] °C per decade, 0.19 [0.10 to 0.40] °C per decade, and 0.17 [0.08 to 0.36] °C per decade for the periods 1998–2011, 1984–1998, and 1951–2011, respectively (the uncertainty ranges assume that the range of the conversion factor to GMST trend and the range of ERF trend itself are independent). The AR5 best-estimate ERF forcing trend difference between 1998–2011 and 1951–2011 thus might explain about one-half (0.04°C per decade) of the observed GMST trend difference between these periods (0.06 to 0.08°C per decade, depending on observational data set).

The reduction in AR5 best-estimate ERF trend over 1998–2011 compared to both 1984–1998 and 1951– 2011 is mostly due to decreasing trends in the natural forcings,–0.14 ± 0.10 W m–2 per decade over 1998–2011 compared to 0.0 ± 0.01 W m–2 per decade over 1951–2011 (Section 8.5.2, Figure 8.19). Solar forcing went from a relative maximum in 2000 to a relative minimum in 2009, with a peak-to-peak difference of around 0.15 W m–2 and a linear trend over 1998–2011 of around –0.10 W m–2 per decade (cf. Section 10.3.1, Box 10.2). Furthermore, a series of small volcanic eruptions has increased the observed stratospheric aerosol loading after 2000, leading to an additional negative ERF linear-trend contribution of around –0.04 W m–2 per decade over 1998–2011 (cf. Section 8.4.2.2, Section 8.5.2).

(Section 8.5.2, Figure 8.19; Box 9.2 Figure 1d,f). By contrast, satellite-derived estimates of tropospheric aerosol optical depth (AOD) suggests little overall trend in global-mean AOD over the last 10 years, implying little change in ERF due to aerosol-radiative interaction (low confidence because of low confidence in AOD trend itself, Section 2.2.3; Section 8.5.1, Table 8.6, Table 8.7; (Murphy, 2013)).

Moreover, because there is only low confidence in estimates of ERF due to aerosol-cloud interaction (Section 8.5.1, Table 8.6), there is likewise low confidence in its trend over the last 15 years. For the periods 1984–1998 and 1951–2011, the CMIP5 ensemble-mean ERF trend deviates from the AR5 best-estimate ERF trend by only 0.01 W m–2 per decade (Box 9.2 Figure 1e,f). After 1998, however, some contributions to a decreasing ERF trend are missing in the CMIP5 models, such as the increasing stratospheric aerosol loading after 2000 and the unusually low solar minimum in 2009.

Nonetheless, over 1998–2011 the CMIP5 ensemble-mean ERF trend is lower than the AR5 best-estimate ERF trend by 0.05 W m–2 per decade (Box 9.2 Figure 1d). Furthermore, global-mean AOD in the CMIP5 models shows little trend over 1998–2012, similar to the observations (Figure 9.29). Although the forcing uncertainties are substantial, there are no apparent incorrect or missing global-mean forcings in the CMIP5 models over the last 15 years that could explain the model–observations difference during the warming hiatus.

© Model Response Error

The discrepancy between simulated and observed GMST trends during 1998–2012 could be explained in part by a tendency for some CMIP5 models to simulate stronger warming in response to increases in greenhouse-gas concentration than is consistent with observations (Section 10.3.1.1.3, Figure 10.4). Averaged over the ensembles of models assessed in Section 10.3.1.1.3, the best-estimate greenhouse-gas (GHG) and other anthropogenic (OA) scaling factors are less than one (though not significantly so, Figure 10.4), indicating that the model-mean GHG and OA responses should be scaled down to best match observations. This finding provides evidence that some CMIP5 models show a larger response to greenhouse gases and other anthropogenic factors (dominated by the effects of aerosols) than the real world (medium confidence). As a consequence, it is argued in Chapter 11 that near-term model projections of GMST increase should be scaled down by about 10% (Section 11.3.6.3). This downward scaling is, however, not sufficient to explain the model-mean overestimate of GMST trend over the hiatus period.

Another possible source of model error is the poor representation of water vapour in the upper atmosphere (Section 9.4.1.2). It has been suggested that a reduction in stratospheric water vapour after 2000 caused a reduction in downward longwave radiation and hence a surface-cooling contribution (Solomon et al., 2010), possibly missed by the models, However, this effect is assessed here to be small, because there was a recovery in stratospheric water vapour after 2005 (Section 2.2.2.1, Figure 2.5).

In summary, the observed recent warming hiatus, defined as the reduction in GMST trend during 1998–2012 as compared to the trend during 1951–2012, is attributable in roughly equal measure to a cooling contribution from internal variability and a reduced trend in external forcing (expert judgment, medium confidence). The forcing trend reduction is primarily due to a negative forcing trend from both volcanic eruptions and the downward phase of the solar cycle. However, there is low confidence in quantifying the role of forcing trend in causing the hiatus, because of uncertainty in the magnitude of the volcanic forcing trend and low confidence in the aerosol forcing trend.

Almost all CMIP5 historical simulations do not reproduce the observed recent warming hiatus. There is medium confidence that the GMST trend difference between models and observations during 1998–2012 is

to a substantial degree caused by internal variability, with possible contributions from forcing error and some CMIP5 models overestimating the response to increasing greenhouse-gas forcing. The CMIP5 model trend in effective radiative forcing (ERF) shows no apparent bias against the AR5 best estimate over 1998–2012.

However, confidence in this assessment of CMIP5 ERF trend is low, primarily because of the uncertainties in model aerosol forcing and processes, which through spatial heterogeneity might well cause an undetected global-mean ERF trend error even in the absence of a trend in the global-mean aerosol loading.

The causes of both the observed GMST trend hiatus and of the model–observation GMST trend difference during 1998–2012 imply that, barring a major volcanic eruption, most 15-year GMST trends in the near-term future will be larger than during 1998–2012 (high confidence; see 11.3.6.3. for a full assessment of near-term projections of GMST). The reasons for this implication are fourfold: first, anthropogenic greenhouse-gas concentrations are expected to rise further in all RCP scenarios; second, anthropogenic aerosol concentration is expected to decline in all RCP scenarios, and so is the resulting cooling effect; third, the trend in solar forcing is expected to be larger over most near-term 15–year periods than over 1998–2012 (medium confidence), because 1998–2012 contained the full downward phase of the solar cycle; and fourth, it is more likely than not that internal climate variability in the near-term will enhance and not counteract the surface warming expected to arise from the increasing anthropogenic forcing.

 

 

 

 

 

 

 

 

Its good they are at least trying to assess the situation with the GCMs and their inability to produce recent flat-lining of temps. However, reading this sounds more like someone mumbling to themselves or brainstorming rather than coherent science. Hopefully they clean it up for the final draft so its more clear. They also never really take a best guess on what they think the major factor is.

[skierinvermont]

How do you know the LIA ended between 1890 and 1930 exactly? If so, it took 1-2 centuries to go into it then why not a century or two to come out of it?? How do you know how quickly the OHC changes in response?  Aerosols in the 50s and 60s?? That is a convenient excuse for the mid 20th century cooling. I have read this before. How about the cold PDO and AMO? Both PDO and AMO cycles can explain pretty much all of the variations in the Earth's temperatures in the last 100 to 150 years. CO2 does have a small influence. But you need feedbacks to make it matter and the paleo data to quantify this is suspect IMO (yes I have read these papers thoroughly). This is because boundary conditions change in times: oceans, H20/clouds the main GHGs, extent of land and glacier, precipitation between during ice ages and interglacials. You don't need CO2 for any of this. CO2 passively follows the temperature trends in the ice core data. That was my epiphany years ago in all this plus CO2 is only a minor GHG. It will cause some small warming but all the feedbacks, clouds etc are not known enough in the real atmosphere. They are "known" in the climate models to some extent but of course these are models and are likely oversensitive based on the observations. Maybe we do equilibriate at 4C(assuming all positive feeback which is highly unlikely IMO)...but that could occur in centuries from the slow ocean heat uptake. Nobody knows the processes or time scales of changing OHC. There is a LOT of water with very high specific heat capacity.   

 

 

How do I know the LIA ended in that period? Because the factors that caused it (solar and volcanic forcing) reverted to extremely strong positive forcings by the early 20th century. If these factors were responsible for not only the early 20th century warming, but also the late 20th and early 21st century warming, there would be a massive energy imbalance, rapidly rising OHC, and rapidly rising temperature early in the 20th century which would then decelerate to the present. 

 

Instead, the earth was probably almost at equilibrium by mid-century as the positive volcanic and solar forcing had maxed out, and anthropogenic forcing was neutral. Thus warming stalled and OHC was almost steady. Only once strong CO2 forcing began in the 70s and 80s did the earth lose its equilibrium, OHC began to rise rapidly, and so did temperature. This imbalance continues to this day.

[blizzard1024]

Tell me blizzard, what happens when hot air passes over water? 

 

It warms!!!

 

What happens when cold air passes over the same body of water?

 

It cools!!!

 

 

Now do you think global warming will cause more warm air or cold air? So do you think the oceans will warm or cool?

 

 

You're just getting lost in abstractions that you don't really understand but are eager to utilize in a way that disproves AGW. Perhaps the more practical exercise above will demonstrate why global warming warms the oceans.

That is not necessarily true. What if the hot air flows over an area of strong upwelling?? There is some heat transfer but the ocean still may cool because the upwelling overwhelms the hot air. If the hot air has a higher dewpoint than the colder waters, fog forms and you can get drizzle which in turn can cause evaporative cooling of the boundary layer which usually could be dry enough. This often is the case if the waters are cold from continued upwelling. The hot air can also run into a ocean/lake boundary and trigger a thunderstorm. If there is dry air at mid levels it could cause surface cooling from evaporation of the precipitation which in turn would keep the waters cool. It is not that simple....the atmosphere is extremely complex.  

 

You just try to simplify everything. CO2 goes up, water vapor goes up, temperatures go up. things are not that simple. no way.   

[skierinvermont]

Perhaps a picture can help. 

 

You can see that the earth was out of equilibrium when the LIA ended as solar and volcanic forcing rose. When they stopped rising, OHC and surface temperature stopped rising as much as well. When CO2 began to rise rapidly (outpacing aerosols) the earth lost its equilibrium again and OHC and surface temperature began to rise again.

[skierinvermont]

That is not necessarily true. What if the hot air flows over an area of strong upwelling?? There is some heat transfer but the ocean still may cool because the upwelling overwhelms the hot air. If the hot air has a higher dewpoint than the colder waters, fog forms and you can get drizzle which in turn can cause evaporative cooling of the boundary layer which usually could be dry enough. This often is the case if the waters are cold from continued upwelling. The hot air can also run into a ocean/lake boundary and trigger a thunderstorm. If there is dry air at mid levels it could cause surface cooling from evaporation of the precipitation which in turn would keep the waters cool. It is not that simple....the atmosphere is extremely complex.  

 

You just try to simplify everything. CO2 goes up, water vapor goes up, temperatures go up. things are not that simple. no way.   

 

 

The question was: How does AGW warm oceans?

 

The answer: by warming the air above the oceans. 

 

 

 

Your example is false. Even if you increase upwelling that body of water as a whole will warm more than the body of water surrounded by cold air. The upwelling of water will not cool the body of water. It will only mix it. 

 

Do you think the northern pacific ocean is warming in summer? Do you think that it is cooling in winter? Warm air warms water. Cold air cools water. 

 

Do you really need to be a rocket scientists to figure this out?

[blizzard1024]

Perhaps a picture can help. 

 

You can see that the earth was out of equilibrium when the LIA ended as solar and volcanic forcing rose. When they stopped rising, OHC and surface temperature stopped rising as much as well. When CO2 began to rise rapidly (outpacing aerosols) the earth lost its equilibrium again and OHC and surface temperature began to rise again.

But CO2 forcing is a small overall. Cloud cover variations and water vapor changes in the upper troposphere which amplify or damp radiative forcing are not fully known. How can you say this? Remember CO2 is a weak GHG.  It only has effect at -50C which is associated with the 15 micron absorption band.  There is no observational evidence that the upper troposphere is warming very much at all. There is also a presentation that shows that the IR opacity of the Earth has changed little in the past 60 years despite increasing CO2. 

 

see  http://climateclash.com/ferenc-miskolczi-the-stable-stationary-value-of-the-earths-ir-optical-thickness/

[tacoman25]

Oh so the +PDO from 1977 to 1983 wasn't really a +PDO because we were in El Nino most of that time?

 

The whole point of the PDO is its relationship to causing/reinforcing/feedback loop with ENSO. 

 

We've been over this before.. just because global temperatures stopped warming when the PDO went negative and started when it went positive.. and then kept rising the second time it went negative... doesn't mean that the PDO was a strong causative factor. Much of the eyeball appearance of correlation is simply due to the fact that +PDOs start with Ninos and -PDOs start with La Ninas so obviously you're going to see sharp changes in temperature whenever the PDO flips (mostly due to ENSO). 

 

Statistically the correlation is nowhere close to being strong enough to suggest causation. Theoretically, causation is already well explained by CO2 and aerosols. There's some wiggle room for some effect of the PDO/ENSO in there but there's not a whole ton of evidence for anything more than a small effect (mostly indirect and short-term through ENSO modulation). 

 

You seem to have an overly simplistic view of the PDO/ENSO relationship. During a +PDO phase, the tendency is towards stronger +PDO, regardless of exact ENSO. During -PDO phase, vice versa. Which is why you'll find that between 1976-2005, even weak +ENSO years often produced significant +PDO....and since then, even weak -ENSO years produce major -PDO. Which was also the case from 1946-1975 during the last -PDO phase.

 

You really think the sudden flip to warming in the late 1970s had very little to do with the PDO phase flip? Or the lack of warming since the early/mid 2000s isn't related to the -PDO phase setting in again?

 

Too many coincidences if you ask me. The oceans are a huge factor in decadal/multi-decadal climate trends, and the PDO is the most powerful oceanic oscillation. 

[blizzard1024]

The question was: How does AGW warm oceans?

 

The answer: by warming the air above the oceans. 

 

 

 

Your example is false. Even if you increase upwelling that body of water as a whole will warm more than the body of water surrounded by cold air. The upwelling of water will not cool the body of water. It will only mix it. 

 

Do you think the northern pacific ocean is warming in summer? Do you think that it is cooling in winter? Warm air warms water. Cold air cools water. 

 

Do you really need to be a rocket scientists to figure this out?

 

The warming of the oceans primarily occurred in the deepest parts. Can you explain that???  The changes we have seen in the OHC are likely a result of PDO and AMO variations.