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

[tacoman25]

We know the PDO affects decadal ENSO and that is reflected in the ONI values provided by NOAA. I'm not sure what the issue here is? The AMO is less understood, but it is clear that it has a much less significant impact to global temperature trends than the PDO/ENSO. Why have the climate models been able to replicate the past 100 years with relative precision if this was not the case?

The issue is that just because climate models can combine a bunch of forcings and replicate past trends to an extent does not mean they have all the factors correct. A lot of the arguments for sulfates being responsible for variations in the temperature trends over the past 50-100 years come from before there was widespread awareness of oceanic cycles like the PDO and AMO. Climate scientists have understood for quite awhile that ENSO affects global temperatures, but they weren't aware of multi-decadal phases like the PDO and AMO really until the past decade or so.

Now that these cycles are becoming more understood, there is a clear correlation with global temps that makes perfect sense given how we know SSTAs effect global temperature. But there is a continued reluctance to accept this correlation, given that aerosols were previously thought to have been the main cause of the flatlining/slight cooling of global temps from the mid 1940s to mid 1970s.

My belief is that many in the AGW proponent crowd inherently want to attribute as much responsibility for temperature trends as possible on humans, and aerosols/sulfates fit that view better. This was why none of the temperature projections from the 1980s and 1990s foresaw the slowdown in global temp rise that occurred over the past 10 years or so. Solar variability was acknowledged as a very small forcing, but only volcanic activity was believed to be a strong enough forcing to cause a slowdown in temperature rise for any meaningful period of time, and even that only for a few years (like what happened with Pinatubo).

It has become apparent that while the underlying physics/warming of AGW theory are very likely to be mostly correct, the climate system is a bit more complex than scientists understood it to be 10, 15, 20 years ago.

[ORH_wxman]

Climate models cannot replicate the early 20th century very well (at least going by typical AR4 GCMs). They underestimate the warming between 1910-1940 and they underestimate the cooling between 1940-1970.

The GCMs get the overall long term trend pretty accurately, but they are not good at caputuring the multi-decadal variation because they are not good at simulating internal oscillations such as ENSO.

[nflwxman]

Climate models cannot replicate the early 20th century very well (at least going by typical AR4 GCMs). They underestimate the warming between 1910-1940 and they underestimate the cooling between 1940-1970.

The GCMs get the overall long term trend pretty accurately, but they are not good at caputuring the multi-decadal variation because they are not good at simulating internal oscillations such as ENSO.

According to the below graph of the AR4 ensemble mean, the only period in which the models clearly missed a long term trend looks to be between 1930-1945, where the GISS data set has the globe a bit warmer. So are sort of correct with that statement. However, I'm having a tough time understanding how the AMO, in particular, has any strong pull on a global temperature trend. The PDO does, but that is largely reflected in the ONI index (which is certainly included in the AR4 models). On can see that ONI values are clearly in a cold phase between 1950-1970 (the years in which cooling occured). Unfortunately, this table only goes back to 1950. While the cool phase of the PDO and lower ONI values may not explain everything, it does probably account for SOME of the cooling period in the mid-20th century. Right now, the sulfate aerosals are blamed as the source of the rest of the cooling at that point. I don't see how that theory can be overturned with a loose correlation.

[skierinvermont]

Outdated. They didn't even try to factor in oceanic cycles into the temperature trend in that graph.

And the sulfate trend there looks considerably different than what skiier illustrated.

That sulfate graph looks different partially because it terminates in 1990.. so it only shows 10 years of the stall not the full 20 on mine or 30 to present.

[skierinvermont]

The issue is that just because climate models can combine a bunch of forcings and replicate past trends to an extent does not mean they have all the factors correct. A lot of the arguments for sulfates being responsible for variations in the temperature trends over the past 50-100 years come from before there was widespread awareness of oceanic cycles like the PDO and AMO. Climate scientists have understood for quite awhile that ENSO affects global temperatures, but they weren't aware of multi-decadal phases like the PDO and AMO really until the past decade or so.

Now that these cycles are becoming more understood, there is a clear correlation with global temps that makes perfect sense given how we know SSTAs effect global temperature. But there is a continued reluctance to accept this correlation, given that aerosols were previously thought to have been the main cause of the flatlining/slight cooling of global temps from the mid 1940s to mid 1970s.

My belief is that many in the AGW proponent crowd inherently want to attribute as much responsibility for temperature trends as possible on humans, and aerosols/sulfates fit that view better. This was why none of the temperature projections from the 1980s and 1990s foresaw the slowdown in global temp rise that occurred over the past 10 years or so. Solar variability was acknowledged as a very small forcing, but only volcanic activity was believed to be a strong enough forcing to cause a slowdown in temperature rise for any meaningful period of time, and even that only for a few years (like what happened with Pinatubo).

It has become apparent that while the underlying physics/warming of AGW theory are very likely to be mostly correct, the climate system is a bit more complex than scientists understood it to be 10, 15, 20 years ago.

Aerosols were not thought to be the primary cause of the cooling because you could create good statistical models with them. It was and is believed because they exert a moderate to strong negative forcing based on obvious physics. The magnitude of any physical causation is understood much better for aerosols than it is for ocean cycles. It's possible that ocean cycles could have helped enhance warming 1910-1945 and cooling thereafter. But aerosols alone can explain most of the multi-decadal variability - and there is good causative reason to believe that that is correct.

You and will like to harp on how the aerosol explanation is all too "convenient" while ignoring the fact that the physical causation is undeniable and aerosols increased fastest from the 1940s to the 1970s. Denying a physical explanation just because it's "convenient" borders on conspiracy theory.

Warming occurred 1910-1945 because of forcing from solar and GHGs was greater than aerosols. Cooling took place thereafter because aerosol forcing was stronger than GHG forcing and solar forcing stabilized. And warming resumed by 1975 because GHG forcing again became stronger than aerosol forcing.

We could probably tweak this general description above by including ocean oscillations.. but most of the variability is already explained by solid physical relationships (solar, TSI, aerosols, and volcanoes)

[ORH_wxman]

Aerosols have a huge "fudge factor" in them. Of course its convenient when you can adjust their feedback level to however you want in the models to fit the curve. Aerosols still don't match as well as the PDO flip in the 2nd half of the 20th century. This isn't denying that aerosols have a cooling effect....its simply asking why the breakdown occurs in the late 1970s while aerosols were still increasing.

The logical answer is that the PDO underwent a large shift and that aerosols are not the main driver of multi-decadal shifts in temperature. More frequent and stronger positive ENSO events will cause a warming trend when you are replacing a period that had more frequent and stronger negative ENSO events.

[WeatherRusty]

Outdated. They didn't even try to factor in oceanic cycles into the temperature trend in that graph.

And the sulfate trend there looks considerably different than what skiier illustrated.

Listen......all the factors on that graph represent external radiative forcing, or something which affects the TOA energy imbalance.

Ocean cycles do not represent external radiative forcing. They are cases of internal temperature variability which carries no long term effects.

Ocean cycles do not belong on that map. Its like saying water vapor as a greenhouse gas is overlooked as a driver of climate change. It is not, because it is not a forcing, water vapor is a feedback. Ocean cycles are not forcings, they are oscillations internal to the climate system..

Ocean cycles present no threat of climate change

[skierinvermont]

Aerosols have a huge "fudge factor" in them. Of course its convenient when you can adjust their feedback level to however you want in the models to fit the curve. Aerosols still don't match as well as the PDO flip in the 2nd half of the 20th century. This isn't denying that aerosols have a cooling effect....its simply asking why the breakdown occurs in the late 1970s while aerosols were still increasing.

The logical answer is that the PDO underwent a large shift and that aerosols are not the main driver of multi-decadal shifts in temperature. More frequent and stronger positive ENSO events will cause a warming trend when you are replacing a period that had more frequent and stronger negative ENSO events.

You can't "fudge" aerosols to have a weak effect one decade and a strong one the next. The uncertainty is whether they have a moderate or strong effect overall.

If the effect is on the weaker side, they probably explain somewhat less of the cooling in 1945-1975. If the effect is stronger, they can explain it single handedly.

But there is every reason to believe that the rapidly increasing aerosol concentrations 1940-1980 had a dramatic cooling effect. Only when you get lost playing around with graphs do you lose sight of this fact.

And just because the warming resumed 5 years before aerosols plateaued doesn't weaken the correlation. There are a number of other factors to consider including ENSO, TSI, GHGs, and -yes- ocean cycles, that could have caused the warming to resume 5 years before aerosols plateaued. There's also the fact that the forcing from aerosols is logarithmic meaning that each incremental increase would have less cooling effect. Which means that by 1970 adding more aerosols was having incrementally smaller effects. Perhaps this is why the warming resumed a bit early.

The best method would be to use the best estimate forcing from solar, aerosols and GHGs, come up with a total forcing, compare that to temperatures.. and then consider the possibility that any remaining residual could be ocean cycles.

Here are a couple such graphs. The blue line in the first graph is forcing, red is temperature. It shows forcing in the 70s being the same as the 40s - and substantially lower in the 60s from multiple volcanoes. Pretty good match. The red line in the second graph is total forcing from solar, aerosols, GHGs (probably other things like land-use changes as well). It shows net forcing of -.3W/m2 from 1950-1975.

As you can see, global temperature is very well predicted by net external forcing alone without any inclusion of internal variability. The only discrepancy is probably the 1940s where temperatures were slightly warmer than net forcing would lead you to believe.

Here's another:

[ORH_wxman]

If you assume aerosols were the main factor behind the 1940-1970 cooling, then you have to explain why they had basically zero fingerprint on the temperatures in the 1910-1940 period despite rising. They were obviously less in that period versus post-1950, however they were increasing nonetheless and temperatures warmed rapidly. I don't doubt that you can use aerosols to explain a lot of the behavior of multidecadal temperature swings, but I do doubt that they explain them better than ocean cycles.

This would lead me to believe they were not the primary factor...rather, they were a secondary (but still significant) factor.

[skierinvermont]

If you assume aerosols were the main factor behind the 1940-1970 cooling, then you have to explain why they had basically zero fingerprint on the temperatures in the 1910-1940 period despite rising. They were obviously less in that period versus post-1950, however they were increasing nonetheless and temperatures warmed rapidly. I don't doubt that you can use aerosols to explain a lot of the behavior of multidecadal temperature swings, but I do doubt that they explain them better than ocean cycles.

This would lead me to believe they were not the primary factor...rather, they were a secondary (but still significant) factor.

Because 1910-1940, GHG forcing was stronger. Also solar was ramping up then big time. It's the emergence from an exceptionally cold period to a period with more GHGs, record high solar activity, and no volcanoes. Aerosols do show a footprint 1910-1940. Without them the warming would have been even faster due to GHGs and solar.

The charts speak for themselves.. add up forcing from GHGs, solar, volcanoes, and aerosols and you can explain nearly all the variability. Very little room or need for ocean cycles to explain observations. And there's no fudging involved. Just take the best estimates based on physics (causation) of how aerosols, GHGs, solar, and volcanoes effect forcing. And then add it all together.

[bluewave]

http://dotearth.blog...entury-climate/

http://www.atmos.col..._Nature2010.pdf

Dotearth had a very long post on the mid-century climate. Other scientists were not sure what to make of the paper

discussed, but said it was a good piece of research.

[ORH_wxman]

Because 1910-1940, GHG forcing was stronger. Also solar was ramping up then big time. It's the emergence from an exceptionally cold period to a period with more GHGs, record high solar activity, and no volcanoes. Aerosols do show a footprint 1910-1940. Without them the warming would have been even faster due to GHGs and solar.

The charts speak for themselves.. add up forcing from GHGs, solar, volcanoes, and aerosols and you can explain nearly all the variability. Very little room or need for ocean cycles to explain observations. And there's no fudging involved. Just take the best estimates of how aerosols, GHGs, solar, and volcanoes effect forcing. And then add it all together.

Its been done...the observational warming is greater than it should be from 1910-1940...if you adjust the aerosols to have less impact so that the 1910-1940 warming matches, then the cooling from 1940-1970 is not explained enough.

Ocean cycles explain the direction and more importantly, the timing of the multi-decadal variations in temperature. As said before, aerosols play a part, but not the primary part there. They are a secondary factor. I'm sorry, but I don't buy that the aerosols magically took effect and reduced their effect at the exact time the PDO phase changes occured.

It makes physical sense from the ocean cycles. ENSO variability from +PDO to -PDO on a 20 year rolling mean can be over 0.5C. Warmer ENSO makes for warmer global temperatures...when it cools, it obviously makes for cooler temperatures.

[skierinvermont]

Its been done...the observational warming is greater than it should be from 1910-1940...if you adjust the aerosols to have less impact so that the 1910-1940 warming matches, then the cooling from 1940-1970 is not explained enough.

Ocean cycles explain the direction and more importantly, the timing of the multi-decadal variations in temperature. As said before, aerosols play a part, but not the primary part there. They are a secondary factor. I'm sorry, but I don't buy that the aerosols magically took effect and reduced their effect at the exact time the PDO phase changes occured.

It makes physical sense from the ocean cycles. ENSO variability from +PDO to -PDO on a 20 year rolling mean can be over 0.5C. Warmer ENSO makes for warmer global temperatures...when it cools, it obviously makes for cooler temperatures.

So you don't buy it because it's too convenient. Gotcha.

Of course the actual data on aerosol concentrations shows that aerosols DID in fact begin to have less impact around 1975.

The charts speak for themselves. Add up the forcing from GHGs, solar, aerosols, and volcanoes and you get a very similar picture to the modern instrumental temperature record. There's some minor discrepancies remaining.. you do notice that the 1940s stick out a bit from the external forcing. Obviously ocean cycles play some role. But are you seriously going to deny the very substantial cooling effect the rapidly growing shroud of haze over the earth must have caused mid century?

[ORH_wxman]

So you don't buy it because it's too convenient. Gotcha.

Of course the actual data on aerosol concentrations shows that aerosols DID in fact begin to have less impact around 1975.

The charts speak for themselves. Add up the forcing from GHGs, solar, aerosols, and volcanoes and you get a very similar picture to the modern instrumental temperature record. There's some minor discrepancies remaining.. you do notice that the 1940s stick out a bit from the external forcing. Obviously ocean cycles play some role. But are you seriously going to deny the very substantial cooling effect the rapidly growing shroud of haze over the earth must have caused mid century?

No, I just think its secondary to ocean cycles. Why would we deny a large shift in the PDO as having a significant effect? We know for a fact that ENSO is a large player in global temperatures.

The charts of the PDO speak for themselves too. The shifts in global temperature were quite sudden both in the late 1940s and late 1970s suggesting that the PDO is more repsonsible rather than aerosols.

[skierinvermont]

No, I just think its secondary to ocean cycles. Why would we deny a large shift in the PDO as having a significant effect? We know for a fact that ENSO is a large player in global temperatures.

The charts of the PDO speak for themselves too. The shifts in global temperature were quite sudden both in the late 1940s and late 1970s suggesting that the PDO is more repsonsible rather than aerosols.

Except it's not just aerosols. It's also solar, volcanoes and GHGs. You have to consider all 4 in concert. Which is what the graphs of total forcing I provided do. And the graphs of total forcing show a rapid increase beginning in the late 70s.

Why? Patially because the cooling effect of aerosols was beginning to slow while the warming effect of GHGs was speeding up. But the sudden jump up in the late 1970s is almost assuredly due to the combination of the above two factors with the high solar activity 1978-1983. You also have the generally +ENSO conditions during that period, but the warming would not have continued after 1983 without GHG forcing > aerosol forcing.

It's very difficult to mentally comprehend the combined forcing of GHGs, aerosols, solar, and volcanoes. Which is why it is best to compare the graph of total forcing vs temperature.

Comparing total forcing vs temperature is much more meaningful than just comparing the PDO index to temperature. We know that the correlation between total forcing and temperature is causative, because total forcing is a measure of the cause of warming. There is no way of knowing how much correlation between the pdo and temperature is causative.

[ORH_wxman]

Except it's not just aerosols. It's also solar, volcanoes and GHGs. You have to consider all 4 in concert. Which is what the graphs of total forcing I provided do. And the graphs of total forcing show a rapid increase beginning in the late 70s.

Why? Patially because the cooling effect of aerosols was beginning to slow while the warming effect of GHGs was speeding up. But the sudden jump up in the late 1970s is almost assuredly due to the combination of the above two factors with the high solar activity 1978-1983. You also have the generally +ENSO conditions during that period, but the warming would not have continued after 1983 without GHG forcing > aerosol forcing.

It's very difficult to mentally comprehend the combined forcing of GHGs, aerosols, solar, and volcanoes. Which is why it is best to compare the graph of total forcing vs temperature.

Comparing total forcing vs temperature is much more meaningful than just comparing the PDO index to temperature. We know that the correlation between total forcing and temperature is causative, because total forcing is a measure of the cause of warming. There is no way of knowing how much correlation between the pdo and temperature is causative.

Your total forcing is using an assumption for the forcing of human aerosols. It fits decently when you do that, but we don't know for a fact what the actual forcing is. Various models have various levels of forcing to try and simulate 20th century temperatures.

The PDO isn't that hard to calculate for the temporary temperature change. The average change in ENSO is about 0.5C to 0.6C on a multi-decadal scale. That is going to cause significant warming or cooling. I don't have the exact numbers off hand, but that type of change in average ENSO is not going to be insignificant to temperatures. The PDO is just a product of ENSO. In addition to the PDO, there was an internal rapid cooling of the Atlantic in the late 1960s and the Pacific temps also accelerated their fall a bit during this time...just not to the extent of the Atlantic.

The sudden drops SSTs in the late 1940s and the sudden rise in the late 1970s is much better explained by internal cycles like the PDO rather than a piece meal of other factors that change on a slower scale than the change in SSTs occured. I'm sure those other factors played a role. I don't buy it was the dominant role though when we are talking about multi-decadal variability.

[skierinvermont]

Aerosols are estimated to have a forcing from pre-industrial climate to 2005 of -1.2W/m2 with a 95% confidence interval from -.6 to -2.4.

Most of the increase in aerosol concentration occurred between 1945-1975. About 2/3s. So we have a best estimate of -.8W/m2 with a 95% confidence interval of -.4 to -1.6W/m2 during this time period.

That equates to a cooling effect of .26C with a 95% confidence interval of .13C to .52C.

So most likely aerosols caused cooling of around .26C from 1945 to 1975. That is almost certainly larger than the cooling effect of the AMO and/or PDO during the period. Had those cycles had an additional cooling effect >.26C we would be talking about a combined cooling effect of.52C+ and the observed cooling in the 1945-1975 would certainly have been larger.

I rest my case. Aerosols are more responsible for the cooling 1945-1975 than the PDO. Even if we accept fairly low estimates of the strength of aerosol forcing lying near the bottom of the 95% confidence interval. You can't just blanket the whole earth in smog and not expect major cooling.

I'll concede a ~2.5% probability that ocean cycles had a stronger influence on global temperature 1945-1975, based on the 2.5% percent probability that aerosol forcing lies on the low side and outside of the 95% confidence interval.

[csnavywx]

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.

BAM. The AMO, by definition is literally equivalent to linearly detrended North Atlantic SST. That's it. Subtract the GISS temp trend from the N. Atl. SST anomaly and whalaa, there IS NO TREND IN THE AMO OVER THE PAST 30+ YEARS. This leads to a second and probably more damning piece of evidence that comes from the fact that the phase shift between temps and the AMO doesn't fit Granger causality. In other words, we should see a positive delay (or time lag) between the AMO and temperature increases. But we don't. We instead see a neutral or even negative delay. This is a serious problem for anyone trying to claim that the AMO drives temperature. Pretty crushing actually. Any valid analysis would have to overcome this and show the full physics of the process. In the meantime, I suppose we'll have to settle for works like this that attempt to chase their own tails with circular reasoning.

A better and much simpler explanation exists besides "mysterious ocean cycles". Global warming. That's right, global warming is the cause... not the effect... of most of the changes in N ATL SST.

[csnavywx]

Aerosols are estimated to have a forcing from pre-industrial climate to 2005 of -1.2W/m2 with a 95% confidence interval from -.6 to -2.4.

Most of the increase in aerosol concentration occurred between 1945-1975. About 2/3s. So we have a best estimate of -.8W/m2 with a 95% confidence interval of -.4 to -1.6W/m2 during this time period.

That equates to a cooling effect of .26C with a 95% confidence interval of .13C to .52C.

So most likely aerosols caused cooling of around .26C from 1945 to 1975. That is almost certainly larger than the cooling effect of the AMO and/or PDO during the period. Had those cycles had an additional cooling effect >.26C we would be talking about a combined cooling effect of.52C+ and the observed cooling in the 1945-1975 would certainly have been larger.

I rest my case. Aerosols are more responsible for the cooling 1945-1975 than the PDO. Even if we accept fairly low estimates of the strength of aerosol forcing lying near the bottom of the 95% confidence interval. You can't just blanket the whole earth in smog and not expect major cooling.

It's funny, because I recently read a paper published from China where they were essentially bitching that photosynthetically available radiation (PAR) was lowered by 5% to 20% (varied by region) by coal-burning aerosols and it was significantly affecting their crop yields.

It's sucks that we don't have better satellite obs for this yet, but the Glory crash last year really set that back and with NASA on a string budget, I don't expect a recovery from that in short order.

I brought up in another post some research by Kaufmann (among others) and the fact that Asian coal use (a very major source of sulfate aerosols) has tripled over the past 12 years or so. There's a new paper out that estimates an immediate warming of .25 to .5C if one were to remove all of the man-made aerosols from the atmosphere. I'll find it in the morning.

[tacoman25]

Aerosols have a huge "fudge factor" in them. Of course its convenient when you can adjust their feedback level to however you want in the models to fit the curve. Aerosols still don't match as well as the PDO flip in the 2nd half of the 20th century. This isn't denying that aerosols have a cooling effect....its simply asking why the breakdown occurs in the late 1970s while aerosols were still increasing.

The logical answer is that the PDO underwent a large shift and that aerosols are not the main driver of multi-decadal shifts in temperature. More frequent and stronger positive ENSO events will cause a warming trend when you are replacing a period that had more frequent and stronger negative ENSO events.

Precisely. Skiier did not address this point at all in his response to me.

[ORH_wxman]

Aerosols are estimated to have a forcing from pre-industrial climate to 2005 of -1.2W/m2 with a 95% confidence interval from -.6 to -2.4.

Most of the increase in aerosol concentration occurred between 1945-1975. About 2/3s. So we have a best estimate of -.8W/m2 with a 95% confidence interval of -.4 to -1.6W/m2 during this time period.

That equates to a cooling effect of .26C with a 95% confidence interval of .13C to .52C.

So most likely aerosols caused cooling of around .26C from 1945 to 1975. That is almost certainly larger than the cooling effect of the AMO and/or PDO during the period. Had those cycles had an additional cooling effect >.26C we would be talking about a combined cooling effect of.52C+ and the observed cooling in the 1945-1975 would certainly have been larger.

I rest my case. Aerosols are more responsible for the cooling 1945-1975 than the PDO. Even if we accept fairly low estimates of the strength of aerosol forcing lying near the bottom of the 95% confidence interval. You can't just blanket the whole earth in smog and not expect major cooling.

I'll concede a ~2.5% probability that ocean cycles had a stronger influence on global temperature 1945-1975, based on the 2.5% percent probability that aerosol forcing lies on the low side and outside of the 95% confidence interval.

Almost all of the derived numbers of aerosol forcing come from inverse calculations which can cause circular reasoning...i.e. the GHG forcing was X, the solar forcing was Y, the temperature changed by Z...therefore the aerosol contribution must be C . Its how almost all of the GCMs have their aerosol values inputted. Regular forward calculations for aerosols have massive error bars to the point of being impractical when trying to attribute them to the cooling period in question. The forward calculations help us figure out that aerosols should cause some cooling effect, but that's about it.

I'm also not sure why you would ignore a significant baseline change in ENSO considering how much you attribute the recent lack of warming to ENSO. These changes in ENSO are not mutually exclusive to the 20th century and the multi-decadal temperature changes are not mutually exclusive to the 20th century. The rise in ENSO in the early 20th century (after a fall in the late 1800s) links well to the rapid warming along with help from solar coming out of the dolrums. There isn't a good reason to pretend the multi-decadal swings from oscillations like ENSO that caused changes in temperatures of several tenths of a degree C stopped existing after 1950 when GHGs started becoming dominant.

[tacoman25]

Listen......all the factors on that graph represent external radiative forcing, or something which affects the TOA energy imbalance.

Ocean cycles do not represent external radiative forcing. They are cases of internal temperature variability which carries no long term effects.

Ocean cycles do not belong on that map. Its like saying water vapor as a greenhouse gas is overlooked as a driver of climate change. It is not, because it is not a forcing, water vapor is a feedback. Ocean cycles are not forcings, they are oscillations internal to the climate system..

Ocean cycles present no threat of climate change

That wasn't the contention. It was the fact that they are an internal modulator of energy and global temperature trends.

[tacoman25]

You can't "fudge" aerosols to have a weak effect one decade and a strong one the next. The uncertainty is whether they have a moderate or strong effect overall.

If the effect is on the weaker side, they probably explain somewhat less of the cooling in 1945-1975. If the effect is stronger, they can explain it single handedly.

But there is every reason to believe that the rapidly increasing aerosol concentrations 1940-1980 had a dramatic cooling effect. Only when you get lost playing around with graphs do you lose sight of this fact.

And just because the warming resumed 5 years before aerosols plateaued doesn't weaken the correlation. There are a number of other factors to consider including ENSO, TSI, GHGs, and -yes- ocean cycles, that could have caused the warming to resume 5 years before aerosols plateaued. There's also the fact that the forcing from aerosols is logarithmic meaning that each incremental increase would have less cooling effect. Which means that by 1970 adding more aerosols was having incrementally smaller effects. Perhaps this is why the warming resumed a bit early.

Only if you ignore the fact that ENSO has a large and well-documented impact on global temperature, and ENSO trends go in phases with the PDO. And PDO phases match up very well with global temperature trends to date. The influence of the AMO is less certain.

[tacoman25]

Except it's not just aerosols. It's also solar, volcanoes and GHGs. You have to consider all 4 in concert. Which is what the graphs of total forcing I provided do. And the graphs of total forcing show a rapid increase beginning in the late 70s.

Why? Patially because the cooling effect of aerosols was beginning to slow while the warming effect of GHGs was speeding up. But the sudden jump up in the late 1970s is almost assuredly due to the combination of the above two factors with the high solar activity 1978-1983. You also have the generally +ENSO conditions during that period, but the warming would not have continued after 1983 without GHG forcing > aerosol forcing.

It's very difficult to mentally comprehend the combined forcing of GHGs, aerosols, solar, and volcanoes. Which is why it is best to compare the graph of total forcing vs temperature.

Comparing total forcing vs temperature is much more meaningful than just comparing the PDO index to temperature. We know that the correlation between total forcing and temperature is causative, because total forcing is a measure of the cause of warming. There is no way of knowing how much correlation between the pdo and temperature is causative.

Yes, and what you're arguing is that solar/volanic/GHG/aerosol impacts just happen to conveniently add up to a trend that also matches major oceanic cycles. But let's just disregard the ocean phases.

FACT: The timing of temperature trend changes matches the PDO phases better than aerosol trend changes.

FACT: ENSO has one of the strongest and most documented physical correlations with global temperature impact.

FACT: ENSO goes through high and low trends in the phases of the PDO.

FACT: The coldest decade of the past 60+ years was the last time period where -PDO/-AMO phases overlapped.

To dismiss the oceanic cycles as significant modulators of global temperature trends the past century is to ignore all these facts and is completely unscientific.

[tacoman25]

Almost all of the derived numbers of aerosol forcing come from inverse calculations which can cause circular reasoning...i.e. the GHG forcing was X, the solar forcing was Y, the temperature changed by Z...therefore the aerosol contribution must be C . Its how almost all of the GCMs have their aerosol values inputted. Regular forward calculations for aerosols have massive error bars to the point of being impractical when trying to attribute them to the cooling period in question. The forward calculations help us figure out that aerosols should cause some cooling effect, but that's about it.

I'm also not sure why you would ignore a significant baseline change in ENSO considering how much you attribute the recent lack of warming to ENSO. These changes in ENSO are not mutually exclusive to the 20th century and the multi-decadal temperature changes are not mutually exclusive to the 20th century. The rise in ENSO in the early 20th century (after a fall in the late 1800s) links well to the rapid warming along with help from solar coming out of the dolrums. There isn't a good reason to pretend the multi-decadal swings from oscillations like ENSO that caused changes in temperatures of several tenths of a degree C stopped existing after 1950 when GHGs started becoming dominant.

Great point. He is willing to acknowledge the role of increased -ENSO (-PDO phase) in trends over the past couple decades (with no proof of aerosols having nearly as much influence on those recent trends), but somehow decides that in the past aerosols were the dominant trend forcing. Just doesn't make any sense.

Skiier is better than this. Very disappointing.

[The_Global_Warmer]

It's funny, because I recently read a paper published from China where they were essentially bitching that photosynthetically available radiation (PAR) was lowered by 5% to 20% (varied by region) by coal-burning aerosols and it was significantly affecting their crop yields.

It's sucks that we don't have better satellite obs for this yet, but the Glory crash last year really set that back and with NASA on a string budget, I don't expect a recovery from that in short order.

I brought up in another post some research by Kaufmann (among others) and the fact that Asian coal use (a very major source of sulfate aerosols) has tripled over the past 12 years or so. There's a new paper out that estimates an immediate warming of .25 to .5C if one were to remove all of the man-made aerosols from the atmosphere. I'll find it in the morning.

Aerosols would also help explain the slowdown in OHC growth as well.

How well mixed are Aerosols?

[The_Global_Warmer]

It's funny, because I recently read a paper published from China where they were essentially bitching that photosynthetically available radiation (PAR) was lowered by 5% to 20% (varied by region) by coal-burning aerosols and it was significantly affecting their crop yields.

It's sucks that we don't have better satellite obs for this yet, but the Glory crash last year really set that back and with NASA on a string budget, I don't expect a recovery from that in short order.

I brought up in another post some research by Kaufmann (among others) and the fact that Asian coal use (a very major source of sulfate aerosols) has tripled over the past 12 years or so. There's a new paper out that estimates an immediate warming of .25 to .5C if one were to remove all of the man-made aerosols from the atmosphere. I'll find it in the morning.

Aerosols would also help explain the slowdown in OHC growth as well.

[skierinvermont]

Almost all of the derived numbers of aerosol forcing come from inverse calculations which can cause circular reasoning...i.e. the GHG forcing was X, the solar forcing was Y, the temperature changed by Z...therefore the aerosol contribution must be C . Its how almost all of the GCMs have their aerosol values inputted. Regular forward calculations for aerosols have massive error bars to the point of being impractical when trying to attribute them to the cooling period in question. The forward calculations help us figure out that aerosols should cause some cooling effect, but that's about it.

I'm also not sure why you would ignore a significant baseline change in ENSO considering how much you attribute the recent lack of warming to ENSO. These changes in ENSO are not mutually exclusive to the 20th century and the multi-decadal temperature changes are not mutually exclusive to the 20th century. The rise in ENSO in the early 20th century (after a fall in the late 1800s) links well to the rapid warming along with help from solar coming out of the dolrums. There isn't a good reason to pretend the multi-decadal swings from oscillations like ENSO that caused changes in temperatures of several tenths of a degree C stopped existing after 1950 when GHGs started becoming dominant.

False. This seems to be a narrative that you have invented over the years on this forum. Radiative forcing from aerosols is not 'invented' as some residual to explain what cannot be explained. It is determined as it is for all the other forcings.. Physics.

Key parameters for determining the direct RF are the aerosol optical properties (the single scattering albedo, ω_o, specific extinction coefficient, k_e and the scattering phase function), which vary as a function of wavelength and relative humidity, and the atmospheric loading and geographic distribution of the aerosols in the horizontal and vertical, which vary as a function of time (e.g., Haywood and Boucher, 2000; Penner et al., 2001; Ramaswamy et al., 2001).

[skierinvermont]

Great point. He is willing to acknowledge the role of increased -ENSO (-PDO phase) in trends over the past couple decades (with no proof of aerosols having nearly as much influence on those recent trends), but somehow decides that in the past aerosols were the dominant trend forcing. Just doesn't make any sense.

Skiier is better than this. Very disappointing.

I am 'willing' (eager) to acknowledge the effect of -ENSO/-PDO in both periods. I have not said it has zero effect. I said the effect is smaller than that of aerosols which probably exerted around .26C of cooling 1945-1975.

Also, I believe the bigger cause of slowed warming since 1998 is solar not -ENSO. Sometimes when people cherry pick shorter trends (like starting in 2002) -ENSO has a bigger effect.

[ORH_wxman]

False. This seems to be a narrative that you have invented over the years on this forum. Radiative forcing from aerosols is not 'invented' as some residual to explain what cannot be explained. It is determined as it is for all the other forcings.. Physics.

Key parameters for determining the direct RF are the aerosol optical properties (the single scattering albedo, ω_o, specific extinction coefficient, k_e and the scattering phase function), which vary as a function of wavelength and relative humidity, and the atmospheric loading and geographic distribution of the aerosols in the horizontal and vertical, which vary as a function of time (e.g., Haywood and Boucher, 2000; Penner et al., 2001; Ramaswamy et al., 2001).

Wrong...read again. I said nearly all of the GCMs use inverse calculations for their aerosols. There are several ways to use inverse calculations. They all don't have to be from a residual in the temperature record if that is what you are assuming. I gave that as one example. More sophisticated inverse calculations are made from assumptions about aerosol size, distribution, etc. I am fully aware there are forward calculations, but the error bars are quite large. The IPCC has an aerosol average error of + or - 1.9 w/m2 when they combine the total forcing directy and indirecty from aerosols.

I don't think you appreciate how uncertain the estimates are in aerosol forcing and all the caveats that are listed when the calculations are made. I'm willing to consider aerosols as the primary factor to the mid-20th century cooling, but right now, I doubt it. They don't explain the huge drop in temperatures even in the first 8-10 years after the PDO flip. Way too sudden and the timning lines up perfectly with the PDO shift.

If we assume the higher aerosol forcing numbers are correct, then that leads to a whole new problem anyway...that much of the recent warming was aided even more by natural variation than first thought.