Depends what caused the warming in the early 20th century, since the post-1975 warming seems to be just a continuation of the 1915-1945 warming (note the similarity of the trends) before a cool PDO phase interrupted the warming.
It can’t have been CO2 as we’ve already established, so what about solar activity. Solar activity began increasing in the early 1900s and continued to increase well into the second half of the 20th century. That’s my theory then.

A combination of ocean circulation and solar activity with possibly a tiny contribution from ghgs.

ask you again….why are the global temperatures warmer now compared to the earlier parts of the last century?

John M (15:43:59) :
“Feel freel to have the last word, since nobody else is reading this thread anymore anyway.”

OK!!

I was giving you the benefit of the doubt, but it appears that you are here to muddy the waters and throw arbitrary, nonsensical arguments around. I should have known from your moniker (is your cousin Michaelina Hunt, known to family and friends as Mike?).

So the 1.6 C/century rate of heating from 1915-1945 was due to the synthetic rubber industry? I have no idea whether that’s what you were trying to say, but it’s a good as any other intepretation I guess.

“It’s these feedbacks which we should be worried about. Frankly I don’t care for an ‘Experiment Earth’ just to see what might happen.”

You are entitled to that opinion. And I don’t want to see another huge speculative experiment with the world economy to address a problem that may not be there.

Since you seem so confident about the upcoming La Nina, maybe you can offer you brilliance to the climate modelers so that can eventually figure out how to get the PDO right.

Feel freel to have the last word, since nobody else is reading this thread anymore anyway.

Mary

You need to spell out exactly what point you are making. If you’re trying to suggest that some minor shift in the relative usage of various industrial processes is enough to not only halt a ~0.15 deg/decade warning trend but to actually reverse it by a similar amount over the next few years then I’m not sure we’re going to get very far. But let’s just consider how aerosols *might* affect the climate

Industrial aerosols (as opposed to volcanic) are short-lived in the atmosphere. They last about 10 days at most before they’re either rained out or dispersed by gravity or other means. This means that their effect is purely regional, i.e. it’s limited to the industrialised regions that produce aerosols. Don’t take my word for it. Papers by Mann & Jones (both pro-AGW scientists) and Levitus et al confirm that the effects of aerosols are “regionally specific”.

So, bearing that in mind, where did the maximum cooling occur between 1944-1975? In Western Europe, perhaps? or the USA? No. The maximum cooling, BY FAR, was in the Arctic. Again don’t take my word for it. Just download the GISS zonal data set and check the cooling trends for each latitude band.

It’s unlikely, therefore, that Industrial aerosols were responsible for the 1944-75 cooling.

In a previous post I stated that increases in CO2 were only a few ppm by the time the ~1915 warming began and it wasn’t that much higher in 1958 long after the warming had ceased. Try as they might, AGWers cannot pin the early 20th century warming on increases in CO2. There just wasn’t enough of an increase to cause the warming. So ….

Increases in CO2 could not be responsible for the 1915-1944 warming.

In other words we can’t really explain the climate with any certainty for the first 75 years of the 20th century. Any models which do claim to simulate the climate have simply tweaked input parameters to achieve the required fit. It’s easy enough to do – I’ve done it myself with various data. I also know of people who have achieved a good fit to the temperature record using just solar activity and ocean circulation. So whose model is right – if any?

Not at all, I’m talking to you, you just ain’t listening.

“It still seems to me that the models do a very poor job of matching the temperature record in the early half on the 20th century,…”

In what way does it ‘seem’ to be a very poor job? As explained above you have to take into account temperature recording and the nature of anomolies. If you look at it then you will se that it is an exceptionally good match, especially after that PDO event is over.

“Be that as it may, the real test will come when the models call for acceleration. Even the models in the graph we’re discussing show only about 0.75C/century warming. We’ll see if the feedbacks kick in.”

It’s these feedbacks which we should be worried about. Frankly I don’t care for an ‘Experiment Earth’ just to see what might happen.

“My guess is that we’ll know a lot more in 5-10 years.”

This is much more than a guess, you can say with certainty we will know a lot more in 5-10 years…but we will have a lot more questions!

“FWIW, it looks like we may be edging back into La Nina conditions .”

Certainly possible but if it does it won’t be anywhere near as strong as last years.

“Note the phrases “causes of the earlier warming are less clear” and “Results from a set of six integrations of a coupled ocean-atmosphere climate model suggest that the warming of the early 20th century could have resulted from a combination of human-induced radiative forcing and an unusually large realization of internal multidecadal variability of the coupled ocean-atmosphere system.

In other words they have no idea.”

For someone who seems intelligent you either misunderstand the English language or just want to deliberately mislead. There is a huge difference between ‘less clear’ and ‘they have no idea’.

“Increased industrialisation apparently causes warming during the early part of the century. But a further increase in industrialisation in the post war years then seems to cause cooling (via aerosols). ”

Again you show a fundamental error in your analysis, I suggest you read up on your 20th century history, concentrate on the Industrial development and then, just maybe you will see that different industrial processes produce different emissions. To help you on your way I’ll give you a starting point:
What industry developed exponentially during the second world war due to the Japanese occupying the asian rubber plantations. I’ll give you a clue: Mr Dunlop…. unless of course you think that industrial emmisions are, have been, and always will be the same!
I think like other deniers you just cant see the bigger picture and spend your time nit picking and cherry picking. The discussion is huge, I mean really huge. The sciences involved vary from meteorology (Mr Watts is an expert in this field), the solar sciences (good ol’ Leif), marine sciences, historians, paleantology, botany, zoology etc etc. Add to this your historians, archaeologists etcand you might just get a grasp on it.

“Mary, even the most ardent warmers have to accept this cannot be the case and tend to accept that increases in ghgs had very little influence on the early 20th century warming. So I’ll ask again – what did cause the warming between 1915 and 1944?”

I have already given the answer, you haven’t answered my question of why the global temperatures are now much warmer than they were between these points….maybe you have..you did mention that CO2 levels were lower then….

I’ve had a quick look at your link .

This is the abstract:

The observed global warming of the past century occurred primarily in two distinct 20-year periods, from 1925 to 1944 and from 1978 to the present. Although the latter warming is often attributed to a human-induced increase of greenhouse gases, causes of the earlier warming are less clear because this period precedes the time of strongest increases in human-induced greenhouse gas (radiative) forcing. Results from a set of six integrations of a coupled ocean-atmosphere climate model suggest that the warming of the early 20th century could have resulted from a combination of human-induced radiative forcing and an unusually large realization of internal multidecadal variability of the coupled ocean-atmosphere system. This conclusion is dependent on the modelÕs climate sensitivity, internal variability, and the speciÞcation of the time-varying human-induced radiative forcing.

Note the phrases “causes of the earlier warming are less clear” and “Results from a set of six integrations of a coupled ocean-atmosphere climate model suggest that the warming of the early 20th century could have resulted from a combination of human-induced radiative forcing and an unusually large realization of internal multidecadal variability of the coupled ocean-atmosphere system.

In other words they have no idea. First thing to remember is that CO2 concentrations in ~1915 were only around 300 ppm. The forcing from this increase is negligible. Also remember there is supposed to be a lag of some 15-20 years before ‘most’ of the temp increase is evident. That, according to the scientists, is the reason we have more warming “in the pipeline”. This study has somehow managed to attribute ~0.5 deg warming to a tiny increase in ghg forcing + what looks to be a change ocean circulation (which is reasonable). Even in 1958 CO2 levels are only 315 ppm. But the thing that gets me about some of this nonsense is this:

Increased industrialisation apparently causes warming during the early part of the century. But a further increase in industrialisation in the post war years then seems to cause cooling (via aerosols).

Mary, even the most ardent warmers have to accept this cannot be the case and tend to accept that increases in ghgs had very little influence on the early 20th century warming. So I’ll ask again – what did cause the warming between 1915 and 1944?

Well it’s clear we’re talking past each other. It still seems to me that the models do a very poor job of matching the temperature record in the early half on the 20th century, and that’s even with assumptions about solar forcing that Leif Svalgaard finds inappropriate ( comment at 11:55:49 here ). Be that as it may, the real test will come when the models call for acceleration. Even the models in the graph we’re discussing show only about 0.75C/century warming. We’ll see if the feedbacks kick in.

My guess is that we’ll know a lot more in 5-10 years. By then, we should either see accelerated warming (more than ~0.1C/decade) to validate the models and assumptions about positve feedbacks, or continued flatness, as one would expect if the cool-phase of the PDO has really kicked in.

FWIW, it looks like we may be edging back into La Nina conditions .

Yes I know about the industrial revolution but you need to get things into perspective. In the early 20th century there were very few cars, almost no aircraft and industrialisation was limited to just a few regions of the world.

But ignoring that for a moment I still ask what what emissions are you talking about, i.e. do you mean CO2 emissions or aerosol emissions ?

” Its just a result of the -ive PDO for that part of the Pacific coast. 1992 isn’t that long ago is it! ”

Whenever someone attempts to “explain” something by saying, “it’s just,” I know there’s no interest in “explaining” anything at all.

“It’s just” the “-ive” (are you texting to us on your cell phone?) PDO?

I’m glad you’ve glanced at a SST anomaly chart and diagnosed “folly.”

So far, I’m quite unimpressed. I do not believe you have succeeded in diagnosing the weather and climate in interior Alaska, the PDO, or anything else.

Is 1992, “that long ago?” Yes it is. Oh, if only we could go back to the CO2 levels of 1992.

While “it’s just” 16 years ago, whether politically, economically, culturally, or climatically, 1992 is significantly long ago.

To believe otherwise just might be folly.

This just shows the folly of using very short term anecdotes. You can see why the temperatures are below normal here http://www.osdpd.noaa.gov/PSB/EPS/SST/data/anomnight.10.6.2008.gif

Its just a result of the -ive PDO for that part of the Pacific coast. 1992 isn’t that long ago is it!

Alaska is Cold

(the polar bears may have temporarily stopped eating each other)

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
145 AM AKDT MON OCT 6 2008

…UNSEASONABLY COLD WEATHER CONTINUES AT FAIRBANKS…

THE HIGH TEMPERATURE YESTERDAY AT THE FAIRBANKS INTERNATIONAL
AIRPORT WAS 31 DEGREES. THIS WAS THE FIRST TIME THIS FALL THAT THE HIGH TEMPERATURE FAILED TO REACH THE FREEZING MARK.

ON AVERAGE THE DATE OF THE FIRST DAY WITH A HIGH TEMPERATURE BELOW FREEZING IS OCTOBER 11TH. SO FAR THIS MONTH THE WARMEST TEMPERATURE OF 38 DEGREES WAS OBSERVED ON THE 2ND.

THE AVERAGE TEMPERATURE SO FAR THIS MONTH OF 27.1 DEGREES IS 8.2 DEGREES BELOW THE 30-YEAR AVERAGE.

IT HAS BEEN THE COLDEST FIRST 5 DAYS OF THE MONTH OF OCTOBER SINCE 1992.

On the contrary, they do have a ‘good handle’ on most of the natural phenomenon but there is always the minutiae, especially in a chaotic system such as climate, these you can allow for but will never be 100% accurate. With PDO’s this is shown in the most recent event, the warm and cool anomolies move around from their ‘text book’ position and this can affect how temperatures are read where temperature recording stations are sparce, such as would have been the case in the Pacific Ocean and North East Asia during the first half of the 20th century. Your argument doesn’t explain the accuracies of the models since the 1950′s, if there wasn’t understanding of “a lot of the natural phenomenon” then the models would not have the accuracy shown.

John Finn (13:06:15) :
“What increased radiative forcing? What emissions? CO2 or something else?
What data do you have to support these increased emissions bearing in mind it’s not the emissions as such but the actual atmospheric concentrations which are most relevant.”

Oh John, you seem to have forgotten your history so to explain, industrial activity has been going on since the British Industrial Revolution. This increased dramatically during and after the First World War, especially in the northern hemisphere. It accelerated again in the ’30′s as governments world wide used increased industrialisation and construction to work their way out of depression and then prepare for war at the end of the ’30′s.

“I don’t think they do. I believe the models rely on solar forcing and reduced volcanic activity to explain the 20th century temp record.”

Whilst these may have a small contribution they do not explain why the temperatures now are higher than they were then. This is the fundamental issue you haven’t attempted to explain.

I can certainly provide a reference: Delworth T. and Knutson T. 2000. Simulation of Early 20th Century Global Warming. Science. vol. 287, pp. 2246-2250.
This explains how one particlular model was a very close fit to observed temperatures without solar or volcanic forcing included. The conclusion would be that there is probably only a very small effect from these forcings.

J John Finn (17:50:33) :

The causes of the early 20th century warming are most probably due to heat transfer fluctuations through the North Atlantic and the North Pacific couple with increased radiative forcing from industrial emmisions

What increased radiative forcing? What emissions? CO2 or something else?
What data do you have to support these increased emissions bearing in mind it’s not the emissions as such but the actual atmospheric concentrations which are most relevant.

Models suggest that there was little or no impact from volcanic activity or solar activity during this time

I don’t think they do. I believe the models rely on solar forcing and reduced volcanic activity to explain the 20th century temp record.

Mary: I’ve read through your response and it looks very much as though it’s been been lifted from an article or an opinion piece. It might be best, therefore, if you provide a link since the extract you’ve provided doesn’t hang together all that well.