New Paper finds Most of the Late-20th Century Warming was Naturally Induced

[Snow_Miser]

There's an interesting new paper that puts the Foster and Rahmstorf study to question. While they found that the long term trend upward of 0.08 Degrees C per decade was mostly anthropogenic over the 20th Century, they found that the late-20th Century Warming was mostly natural, with Greenhouse Gases and other factors they did not remove contributing only 40%.

http://journals.amet...JAS-D-12-0208.1

[ORH_wxman]

The presentation with slides is here:

http://www.tims.ntu.edu.tw/download/talk/20120918_2297.pdf

I havent read it yet, but am doing so now. That seems to be a large claim. I had linked another recent paper months ago that showed perhaps one third of the warming in the 1975-2005 period was natural. I actually wish I could find that paper to compare it.

[skierinvermont]

Everything I have read by Zhou to date has been garbage. Hope this is better.

[WeatherRusty]

This is the important point to take away from the abstract:

The deduced net anthropogenic global warming trend has been remarkably steady and statistically significant for the past 100 years.

The variations in warming rate are a wash.

The James Inhofes of the world should take note. It's not a hoax even if climate sensitivity is relatively low, but we don't know that do we! If it warms even another 1C over the next 100 years we have serious issues. That's the low end outcome on the probability distribution.

[skierinvermont]

The forcing from CO2 over the period is over 1W/m2. That is more than enough to cause most of or all of the warming over the period.

[rygar]

Makes sense. Warming is caused by mankind and natural variability.

[tacoman25]

This is the important point to take away from the abstract:

The deduced net anthropogenic global warming trend has been remarkably steady and statistically significant for the past 100 years.

The variations in warming rate are a wash.

The James Inhofes of the world should take note. It's not a hoax even if climate sensitivity is relatively low, but we don't know that do we! If it warms even another 1C over the next 100 years we have serious issues. That's the low end outcome on the probability distribution.

1C/100 years is plenty slow enough to adapt. There is no evidence that another 1C would cause significantly accelerated sea rise, which is the most concrete concern in regards to AGW.

[WeatherRusty]

1C/100 years is plenty slow enough to adapt. There is no evidence that another 1C would cause significantly accelerated sea rise, which is the most concrete concern in regards to AGW.

Adaptation is expensive, obviously this country and many others are having fiscal troubles with current day issues, never mind the addition of massive public works projects necessitated by sea level rise, depleted and contaminated ground water supplies, agricultural shifts, droughts, flooding. We will have great difficulty with these things, and we are the richest nation in the world. How will others fare?

The entire paleoclimate record indicates that as temps rise so does sea level, and the changes are measured in feet to many dozens of feet for another 1 or 2C.

What about the extinction rate of species we share the planet with?

[tacoman25]

Adaptation is expensive, obviously this country and many others are having fiscal troubles with current day issues, never mind the addition of massive public works projects necessitated by sea level rise, depleted and contaminated ground water supplies, agricultural shifts, droughts, flooding. We will have great difficulty with these things, and we are the richest nation in the world. How will others fare?

The entire paleoclimate record indicates that as temps rise so does sea level, and the changes are measured in feet to many dozens of feet for another 1 or 2C.

What about the extinction rate of species we share the planet with?

As I've pointed out many times before, the history of humanity is full of adaption. The amount of sea level rise likely with 1C over 100 years would not require any more adaption than we've had to go through before. The earth's climate has seen similar shifts many times before (and more severe when heading into an ice age, obviously).

The underlying fiscal problems that many nations are currently facing is a whole different issue, and quite frankly dealing with possible sea level rise is not nearly the gravest problem that could be exacerbated by these financial issues. I think political upheaval, war, and infrastructure collapse are greater risks facing the world in the near future.

[Snow_Miser]

This is the important point to take away from the abstract:

The deduced net anthropogenic global warming trend has been remarkably steady and statistically significant for the past 100 years.

The variations in warming rate are a wash.

The James Inhofes of the world should take note. It's not a hoax even if climate sensitivity is relatively low, but we don't know that do we! If it warms even another 1C over the next 100 years we have serious issues. That's the low end outcome on the probability distribution.

Yes.

The long term 100 year trend in Global Temperatures according to the authors is mostly anthropogenic. However, on timescales like the early 20th and late-20th Century, this would also mean that natural variability contributes significantly to such steep increases in warming, something that Will and Tacoman have both been saying on this forum. It also questions the validity of the Foster and Rahmstorf's "anthropogenic trend" over the last 30 years, as the anthropogenic trend derived by Tung and Zhou is less than half of that derived by Foster and Rahmstorf over the last 30 years, and as the powerpoint that Will linked to shows, it is a pretty controversial idea.

[Snow_Miser]

The forcing from CO2 over the period is over 1W/m2. That is more than enough to cause most of or all of the warming over the period.

That determines how sensitive the climate system is, which is still currently an unknown.

[skierinvermont]

That determines how sensitive the climate system is, which is still currently an unknown.

Huh? That is not what it means at all. 1+ W/m2 is the radiative forcing from CO2 alone since the mid 20th century. That has nothing to do with climate sensitivity.

That is enough radiative forcing to cause most or all of the late 20th century warming.

[skierinvermont]

Well I've made it through the abstract and have already found their mistake. Anybody want to venture a guess?

[PhillipS]

Well I've made it through the abstract and have already found their mistake. Anybody want to venture a guess?

Are you referring to the abstract's sentence "ENSO and volcano aerosols have very little multi-decadal trend." when, in fact, ENSO has no trend by definition (it's the detrended Atlantic SSTs), and volcanic eruptions are random events without trends either?

[ORH_wxman]

Are you referring to the abstract's sentence "ENSO and volcano aerosols have very little multi-decadal trend." when, in fact, ENSO has no trend by definition (it's the detrended Atlantic SSTs), and volcanic eruptions are random events without trends either?

ENSO is in the Pacific ocean.

[CoastalWx]

Well ENSO does sort of mirror the PDO.

[PhillipS]

ENSO is in the Pacific ocean.

Oops, you're right, I'm wrong. I was thinking AMO

[ORH_wxman]

Well ENSO does sort of mirror the PDO.

Yeah there is definitely a multi-decadal oscillation of ENSO...the AMO has a more robust looking oscillation but the ENSO one is definitely there...and the PDO is the reflection of that.

[Snow_Miser]

Huh? That is not what it means at all. 1+ W/m2 is the radiative forcing from CO2 alone since the mid 20th century. That has nothing to do with climate sensitivity.

That is enough radiative forcing to cause most or all of the late 20th century warming.

If Climate Sensitivity were 8 w/m^2/K then it would not nearly be enough. That's why climate sensitivity is important when making such a claim.

[Snow_Miser]

Yeah there is definitely a multi-decadal oscillation of ENSO...the AMO has a more robust looking oscillation but the ENSO one is definitely there...and the PDO is the reflection of that.

This study includes the removal of the impact of the multidecadal oceanic oscillations from the temperature data, which was one of the factors that I suggested could still have been within the Foster and Rahmstorf "anthropogenic trend" over the last 30 years in the other thread, and they get a signifiantly smaller anthropogenic trend over the last 30 years than Foster and Rahmstorf did.

Coincidence?

[skierinvermont]

If Climate Sensitivity were 8 w/m^2/K then it would not nearly be enough. That's why climate sensitivity is important when making such a claim.

There is zero evidence to support anything close to 8 w/m2/K, and tons of evidence against it from paleoclimate and theoretical physics. The ice ages could never have happened if climate sensitivity was 8 w/m2/K. It is most likely between .74-1.85 W/m2/K.

[Snow_Miser]

There is zero evidence to support anything close to 8 w/m2/K, and tons of evidence against it from paleoclimate and theoretical physics. The ice ages could never have happened if climate sensitivity was 8 w/m2/K. It is most likely between .74-1.85 W/m2/K.

I was providing an example that sensitivity most certainly does matter in terms of how much warming a forcing causes. I agree that 8 w/m^2/K is probably too low of a sensitivity. A sensitivity of 5.5 w/m^2/K would not be sufficient enough either, and is a sensitivity that I find to be quite plausable.

[skierinvermont]

The error is that they think they can filter out the AMO the same way ENSO, TSI, and volcanoes are filtered out and be just as confident that the correlations are causative. Think about the correlation to ENSO. There have been dozens of cycles up and down and we can be very confident the correlation is causative. Even with TSI there have been almost a dozen cycles so we can be very confident the correlation is causative. And with volcanoes, the occurrence of volcanoes is intermittent but intense.

The AMO on the other hand, we have basically two complete cycles. All we need is some variable that goes up down up over 120 years. That's not nearly enough to be sure the correlation is causative. It's really very similar to how deniers point out that the inverse of the number of pirate attacks correlates well to temperature.

All this is a silly correlation based study that tells us absolutely nothing that looking at this chart doesn't already tell you. We've all seen this chart before, but nobody would seriously claim to know whether the correlation is causative. Neither can this study.

[skierinvermont]

I was providing an example that sensitivity most certainly does matter in terms of how much warming a forcing causes. I agree that 8 w/m^2/K is probably too low of a sensitivity. A sensitivity of 5.5 w/m^2/K would not be sufficient enough either, and is a sensitivity that I find to be quite plausable.

There is also zero support for a climate sensitivity of 5.5 w/m2/K and tons of evidence against it. The ice ages could not have happened. It would require a forcing of 30+ W/m2.

[Snow_Miser]

There is also zero support for a climate sensitivity of 5.5 w/m2/K and tons of evidence against it. The ice ages could not have happened. It would require a forcing of 30+ W/m2.

We have little to no idea about the processes that were involved in the Earth's climate changes in the past, thus we have little to no idea about what the magnitude of those forcings were when they were impacting Earth's Climate during the Ice Ages.

That is also why many scientists get wildly different values when they try and extract Earth's Climate Sensitivity based off of paleoclimatological data. If GCRs were the primary driver of paleoclimate, then the sensitivity matches up with the paleoclimatological data. The problem is that we still do not have a good grasp with as to what the factors were that caused the Earth's Climate to change in the past, so this is still an area of uncertainty.

http://www.clim-past...8-4923-2012.pdf

http://www.uibk.ac.a...pdf/christl.pdf

http://stephenschneider.stanford.edu/Publications/PDF_Papers/shaviv-veizer-03.pdf

http://elpub.wdcb.ru...04163.htm#ref50

[Snow_Miser]

The error is that they think they can filter out the AMO the same way ENSO, TSI, and volcanoes are filtered out and be just as confident that the correlations are causative. Think about the correlation to ENSO. There have been dozens of cycles up and down and we can be very confident the correlation is causative. Even with TSI there have been almost a dozen cycles so we can be very confident the correlation is causative. And with volcanoes, the occurrence of volcanoes is intermittent but intense.

The AMO on the other hand, we have basically two complete cycles. All we need is some variable that goes up down up over 120 years. That's not nearly enough to be sure the correlation is causative. It's really very similar to how deniers point out that the inverse of the number of pirate attacks correlates well to temperature.

All this is a silly correlation based study that tells us absolutely nothing that looking at this chart doesn't already tell you. We've all seen this chart before, but nobody would seriously claim to know whether the correlation is causative. Neither can this study.

So you're saying that because correlation does not mean causation, the AMO has a smaller impact that what is reported in the paper?

[skierinvermont]

We have little to no idea about the processes that were involved in the Earth's climate changes in the past, thus we have little to no idea about what the magnitude of those forcings were when they were impacting Earth's Climate during the Ice Ages.

That is also why many scientists get wildly different values when they try and extract Earth's Climate Sensitivity based off of paleoclimatological data. If GCRs were the primary driver of paleoclimate, then the sensitivity matches up with the paleoclimatological data. The problem is that we still do not have a good grasp with as to what the factors were that caused the Earth's Climate to change in the past, so this is still an area of uncertainty.

http://www.clim-past...8-4923-2012.pdf

http://www.uibk.ac.a...pdf/christl.pdf

http://stephenschnei...v-veizer-03.pdf

http://elpub.wdcb.ru...04163.htm#ref50

There is no plausible mechanism by which GCRs could alter the earth's energy budget by 30+ W/m2.. there's no plausible mechanism by which they could have much effect at all.

GCRs are at record levels and yet there has been no perceptible effect on global temperatures or the earth's energy balance. The idea is nonsense at this point. (this is where you propose some magical nonsensical 10+ year delay from the initial change in GCRs to any perceptible effect on earth whatsoever).

Paleoclimate studies conclude sensitivity is around 1W/m2/K. This is also confirmed by the response to volcanic eruptions such as Pinatubo. And again by modeling.

[tacoman25]

The error is that they think they can filter out the AMO the same way ENSO, TSI, and volcanoes are filtered out and be just as confident that the correlations are causative. Think about the correlation to ENSO. There have been dozens of cycles up and down and we can be very confident the correlation is causative. Even with TSI there have been almost a dozen cycles so we can be very confident the correlation is causative. And with volcanoes, the occurrence of volcanoes is intermittent but intense.

The AMO on the other hand, we have basically two complete cycles. All we need is some variable that goes up down up over 120 years. That's not nearly enough to be sure the correlation is causative. It's really very similar to how deniers point out that the inverse of the number of pirate attacks correlates well to temperature.

All this is a silly correlation based study that tells us absolutely nothing that looking at this chart doesn't already tell you. We've all seen this chart before, but nobody would seriously claim to know whether the correlation is causative. Neither can this study.

I wouldn't call it an "error". It's just using the correlation that is there. When the PDO is overlayed with the AMO, the correlation to global temp trends is even stronger.

I think it would be silly to ignore or dismiss an obvious longterm correlation with oceanic cycles that makes sense, in terms of affecting global temp trends.

Any objective person can see that natural cycles played a role in warming over the past few decades. This study might overestimate that role, but many other studies have overlooked it.

[WeatherRusty]

The best estimate for equilibrium climate sensitivity is on the order of 0.75K per watt forcing.... Thus we get nearly 3K of warming from a radiative forcing equaling 3.7w/m^2. This is the consensus value derived from many, many sensitivity studies. You can find studies which are far outliers to suit your bias, however they are just that....outliers.

[skierinvermont]

I wouldn't call it an "error". It's just using the correlation that is there. When the PDO is overlayed with the AMO, the correlation to global temp trends is even stronger.

I think it would be silly to ignore or dismiss an obvious longterm correlation with oceanic cycles that makes sense, in terms of affecting global temp trends.

Any objective person can see that natural cycles played a role in warming over the past few decades. This study might overestimate that role, but many other studies have overlooked it.

Adding them together doesn't improve it at all. I assume you are referring to that conconcted graph created by some denier site that manipulated or distorted the data somehow to make it look much better than it is. Below is a graph I created of the PDO+AMO vs temp. As you can see it's not very similar to the denier site version. The denier graph shows the PDO+AMO peaking in 2000, while my graph shows that it is actually near zero.