matty

Global Warming is Not a Crisis

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waitforufo    107

Did the ICPP projection include the longer than normal solar minimum, which we have recently experienced?

Did the ICPP projection include the larger than expected melting of polar ice, which we have recently experienced?

 

Interesting questions. The first attacks the credibility of climate models for not including the effects solar cycles. The second attacks the credibility of climate models for not considering the negative feedback of melting polar ice.

 

Why would anyone consider fundamentally changing our economy and culture based on computer models that do not include such well known climate forcings? I appreciate that these well known forcings are perhaps not well understood, but perhaps if warmthers were not intentionally avoiding negative forcings, because negative forcings detract from their funding and politically driven narrative, they just might find out that CO2 is climate benign.

 

If recent temperatures don't match the models because of longer solar minimums and unexpected polar ice melting, why would it not be reasonable to assume that the slight warming of the past 150 years was not caused by other neglected factors instead of CO2?

 

I hope you didn't think your questions were in defense of climate models. All they do is point out that we simply don't know enough to make decisions. Particularly decisions which will divert funds from known actual problems.

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iNow    4503
I hope you didn't think your questions were in defense of climate models. All they do is point out that we simply don't know enough to make decisions. Particularly decisions which will divert funds from known actual problems.

Such as the deep and willful ignorance that we see so frequently and proudly displayed amongst large swaths of the population?

 

That's another actual problem that could use addressing, I agree, but it turns out we can do more than one thing at once.

Edited by iNow

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swansont    6167

Let's compare the A1b models as initialised in 1990 to all the major temperature series, as I did back in post #156

 

What were the inputs to the A1b model? It looks to me like this assumes an aggressive increase in the CO2 levels. Have they been borne out in reality? Also, as with the other graph, it appears that the projection temperatures and the actual temperatures do not match up at the starting point. So it looks like you have an offset making reality appear to be lower than the projection by 0.2 ºC

 

Interesting questions. The first attacks the credibility of climate models for not including the effects solar cycles. The second attacks the credibility of climate models for not considering the negative feedback of melting polar ice.

 

This is not an attack on the models. This is a question about which scenario to use, because the model output depends on the model input. As in: I predict that if you are out of bread, you will go to the store. You are not out of bread, so you didn't go to the store. Is my model wrong?

 

Why would anyone consider fundamentally changing our economy and culture based on computer models that do not include such well known climate forcings?

 

Because we aren't? This characterization is false.

 

I appreciate that these well known forcings are perhaps not well understood, but perhaps if warmthers were not intentionally avoiding negative forcings, because negative forcings detract from their funding and politically driven narrative, they just might find out that CO2 is climate benign.

 

If recent temperatures don't match the models because of longer solar minimums and unexpected polar ice melting, why would it not be reasonable to assume that the slight warming of the past 150 years was not caused by other neglected factors instead of CO2?

 

Why assume when you can do, you know, actual science?

 

I hope you didn't think your questions were in defense of climate models. All they do is point out that we simply don't know enough to make decisions. Particularly decisions which will divert funds from known actual problems.

 

Who is "we" in this scenario?

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waitforufo    107

This is not an attack on the models. This is a question about which scenario to use, because the model output depends on the model input. As in: I predict that if you are out of bread, you will go to the store. You are not out of bread, so you didn't go to the store. Is my model wrong?

 

I don't really understand your point but yes it's wrong, I went to the store to get milk.

Since you left out my milk desire forcing your model fails to accurately predict my going to the store behavior. Leaving out forcings is a bad idea. Is that your point?

 

Why assume when you can do, you know, actual science?

 

Perhaps you are not aware that actual science knows that sun spot activity impacts climate. My first attempt Google search found this paper. So why doesen't climate science attempt to accurately include sun spot cycles in their models. Perhaps it is because they need to have a handy reason for thee failures of their models.

 

http://naldc.nal.usda.gov/download/CAT76674961/PDF

 

Perhaps those climate deniers over that USDA have been hiding this report from climate modelers.

 

Who is "we" in this scenario?

 

In general by "we" I mean human beings. Sure there are a few human beings that have become too entrenched in their position to see reason but they are the minority. For example look again at this survey I posted recently.

 

304x553xPew-copy.jpg.pagespeed.ic.Jf-zxK_zv2.jpg

 

People in this survey were asked to rank 25 items in order of importance. Climate warming came in dead last.

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swansont    6167

I don't really understand your point but yes it's wrong, I went to the store to get milk.

Since you left out my milk desire forcing your model fails to accurately predict my going to the store behavior. Leaving out forcings is a bad idea. Is that your point?

 

No. I quite clearly stated that you did not go to the store. You don't get to change my example. Regardless, your example is a logical fallacy. That you went to the store means nothing. This is an example about conditional statements. Don't move the goalposts.

 

 

What forcings are being left out of the models?

 

 

Perhaps you are not aware that actual science knows that sun spot activity impacts climate. My first attempt Google search found this paper. So why doesen't climate science attempt to accurately include sun spot cycles in their models. Perhaps it is because they need to have a handy reason for thee failures of their models.

 

Present proof that the models don't include sunspot effects on solar irradiance. You have made this claim. Back it up.

 

 

In general by "we" I mean human beings. Sure there are a few human beings that have become too entrenched in their position to see reason but they are the minority. For example look again at this survey I posted recently.

 

304x553xPew-copy.jpg.pagespeed.ic.Jf-zxK_zv2.jpg

 

People in this survey were asked to rank 25 items in order of importance. Climate warming came in dead last.

 

In that regard, then I agree that "we simply don't know enough to make decisions". If you are ill-informed, you should not make decisions. But the "we" excludes people who do this kind of investigation for a living.

 

Since when does a policy survey tell you what the correct science is?

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Essay    87
If recent temperatures don't match the models because of longer solar minimums and unexpected polar ice melting, why would it not be reasonable to assume that the slight warming of the past 150 years was not caused by other neglected factors instead of CO2?

 

 

... they just might find out that CO2 is climate benign.

But these weren't neglected factors. If you think there are neglected factors, you could get rich pointing them out!

 

I remain skeptical of your hope that "they just might find [it's] ...benign." CO2 is demonstrated, through physics reproduced for over a century now, to be climate active. On what do you base your hope?

 

 

 

p.s. I'm not a working expert in climate models, so I'll welcome a more accurate explanation ...if my details are wrong; but the overall comprehension should still be valid.

Interesting questions.

 

I hope you didn't think your questions were in defense of climate models. All they do is point out that we simply don't know enough to make decisions. Particularly decisions which will divert funds from known actual problems.

...I think we "know enough...."

 

 

I think you're confusing responses to short-term and very transitory changes in the system, with the responses expected from long-term, relatively permanent, forcers-- and then judging the model by that.

 

The reply was about "missing heat" and I can see how, from my rhetorical questions above (#250), you might think those aspects (solar and ice sheets) are not included in the models, but....

 

They are included, though they are not themselves modeled. In other words, we don't have models of how solar activity or ice sheet dynamics will evolve, so they can only include a "constant" or a "trend" that becomes part of the baseline upon which the modeled forcers then act and evolve.

 

For the sun, this "assumption" of nearly constant activity (within the limits of sunspot cycles) is detailed in the IPCC reports. Please note that models such as this are to indicate long-term trends, which is why the recent hiccup in the sunspot cycle shouldn't affect the long-term results (but may affect short term observations).

 

It is also why pointing to a sub-decadal divergence in temperature, as a flaw, is misleading. If the sun's hiccup turns into a long-term change in solar activity, then the models will need to readjust their existing solar component. And so until that time, the sun is still accounted for in the models.

===

 

For the Ice Sheets, the solution has less supporting evidence. Climate models works well at simulating the response to various ice-sheet scenarios, but we have no good way to predict which ice-sheet scenario will develop. There is no clear way to validate a model of ice sheet dynamics, not that there are many; nor are there good paleorecords of ice sheet responses.

 

So as with solar forcings, they plug in a constant or constant trend (I'm oversimplifying, but relatively it conveys the picture), and watch the system evolve when given a certain polar albedo, etc., determined by the "expected" ice-sheet cover.

 

The news about Arctic melting over the past decade has shown that the IPCC projections for Ice-Sheet decay trends were too conservative, underestimating the melting--the loss of ice thickness, and the decreasing extent of ice cover. If this turns out to be more than a hiccup, and instead turns into a progressing trend, then the models will need to recalculate how quickly climate responses may be expected over the next century.

===

 

These points about the solar cycle or Arctic melting are more like a new volcano erupting and changing weather for a few years, but which were not included in the climate models. Either they become explainable hiccups in the model, or they become a new trend that needs to be accounted for.

 

Climate science still operates like all the other sciences. It's a circle of observations and predictions, and observing discrepencies and refining predictions; explaining what we see, what we have seen, and what we can expect to see....

===

 

All this concern about recent temperature trends misses the big point about how we are changing the atmospheric chemistry of our only home, and how this is affecting weather extremes, water resources, and ocean and soil chemistry--and their consequent food webs.

 

~ ohmy.gif

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swansont    6167

Yes, but it's not just CO2 that causes changes.

 

I don't think anyone is claiming that this is the case.

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iNow    4503

Yes, but it's not just CO2 that causes changes.

As swansont already noted... no sh*t, Sherlock. :rolleyes:

 

I'm unsure if this is your stance or not FX, but this reminds me of those who regularly say that climate change has happened in the past naturally for millions of years, so anthropogenic climate change must be untrue. It's as if they're arguing that because forest fires have happened naturally in the past humans couldn't possibly start one. It's downright awe inspiring how so many people can't seem to fathom that there are fatal flaws in their logic and reasoning on this issue (the same applies to those who think the potential downstream economic impact of mitigating these issues has any bearing whatsoever on negating the science that informs the conclusions).

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swansont    6167

Or that "the warming is from natural causes" somehow means that the details are a mystery — that we could not determine what the contributions are.

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D H    1371
I'm unsure if this is your stance or not FX, but this reminds me of those who regularly say that climate change has happened in the past naturally for millions of years, so anthropogenic climate change must be untrue. It's as if they're arguing that because forest fires have happened naturally in the past humans couldn't possibly start one.

That is indeed the argument some make, and it is downright naive or downright dishonest (or both; every movement has its useful idiots).

 

Nature causes some pretty nasty forest fires, and yet we know that people do start forest forests and we do worry about those forest fires caused by people. Nature causes some downright massive erosion (just take a trip to the Grand Canyon), and yet we do know that some farming practices foster erosion and we do worry about that erosion caused by mankind. So why is it that just because natural climate variations (perhaps even some extinction level events) are much more severe than what we are seeing now mean that we are not the cause of this particular warming episode, or that we should do nothing about it?

Edited by D H
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Essay    87

Yes, but it's not just CO2 that causes changes.

 

New paper on radiative forcings and such. Reconciling anthropogenic climate change with observed temperature 1998–2008, Kaufmann et al, PNAS (2011).

 

Thanks!

 

This paper, which includes Michael Mann as an author, only backs up the suggestion that short-term fluctuations in transient forcers will lead to deviations from the long-term projections. These do not change the impact of long-term, relatively permanent forcers such as CO2.

 

Declining solar insolation as part of a normal eleven-year cycle, and a cyclical change from an El Nino to a La Nina dominate our measure of anthropogenic effects because rapid growth in short-lived sulfur emissions partially offsets [the effect of] rising greenhouse gas concentrations. As such, we find that recent global temperature records are consistent with the existing understanding of the relationship among global surface temperature, internal variability, and radiative forcing, which includes anthropogenic factors with well known warming and cooling effects.

 

 

—a rapid rise in anthropogenic sulfur emissions driven by large increases in coal consumption in Asia in general, and China in particular. Chinese coal consumption more than doubles in the 4 y from 2003 to 2007 (the previous doubling takes 22 y, 1980–2002). In this four year period, Chinese coal consumption accounts for 77% of the 26% rise in global coal consumption.

 

Yikes! Over 5x the rate ...and still increasing, I imagine....

This may become more than a transient forcer. I wonder if they are having acid rain problems... or if Japan is, or if Alaska or the Arctic are having acid snow problems....

 

~ ohmy.gif

Edited by Essay

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Edtharan    408

Interesting questions. The first attacks the credibility of climate models for not including the effects solar cycles. The second attacks the credibility of climate models for not considering the negative feedback of melting polar ice.

 

Why would anyone consider fundamentally changing our economy and culture based on computer models that do not include such well known climate forcings? I appreciate that these well known forcings are perhaps not well understood, but perhaps if warmthers were not intentionally avoiding negative forcings, because negative forcings detract from their funding and politically driven narrative,

Many of the climate models do account for the solar cycles, so this argument that they don't take them into account is false.

 

But, solar cycles are actually a fairly short term effect compared to the effect of greenhouse gasses. The Sun has an 11 year solar cycle (5.5 years from peak to minimum), where as the effects of greenhouse gasses are taken over 50 to 100 years. Also, the variation in energy over that is not much compared to the amount of energy retained though greenhouse gasses. And, the variation is both positive (peak) and negative (minimum) which over the short period it occurs tends to cancel itself out.

 

So, there are models that include the solar cycles, but other leave it out because it has been shown not to have a significant effect on the results.

 

they just might find out that CO2 is climate benign.

Well, it is a known fact that CO2 blocks and then re-emits infra-red light (effectively scattering it). The experiment to do this is not hard and can typically be done in most collage science labs (I have done it myself).

 

It is also a know fact that the only way the Earth can loose energy is to radiate this energy out as radiation.

 

Measurements have shown that this energy is mainly in the infra-red spectrum, just the same spectrum that CO2 scatters.

 

Now, as I have shown earlier, if you reduce the rate of loss in a system, then the amount of stuff retained by the system increases (bank accounts are a perfect example of this in action).

 

If the Earth retains energy in the form of infra-red radiation, then this will act as a warming effect (among other things).

 

From this we can conclude that CO2 is not "climate benign", so your argument that it could be, must be false. More so, it shows that there will be increases in temperatures due to an increase in CO2, but also, as this IR radiation can deliver energy into the system (usually through local warming rather than global warming), this increase in energy within the Earth's climate systems can lead to disruptions of those systems.

 

If recent temperatures don't match the models because of longer solar minimums and unexpected polar ice melting, why would it not be reasonable to assume that the slight warming of the past 150 years was not caused by other neglected factors instead of CO2?

Actually the "unexpected" polar ice melting was unexpected in climate change denier circles. For a long time they have been saying that there won't be any increase in polar melting. Interestingly, now that it has occurred, and occurred slightly faster and in greater amounts than the lowest predictions of climate scientists, they are claiming that because deniers cherry picked models that didn't predict this amount of melting got it wrong, then climate change must be wrong.

 

Think about this. An effect predicted by climate scientists and denied by the deniers actually occurs, but because it didn't fit exactly every single model out there, the deniers are now using this effect as proof against climate change.

 

It is like me predicting that if I flip a coin a number of times, and that the number of heads will be roughly 50%, but when I do it, I got 55% heads, and then you using that to prove that coins with tails on them don't exist.

 

I hope you didn't think your questions were in defense of climate models. All they do is point out that we simply don't know enough to make decisions. Particularly decisions which will divert funds from known actual problems.

I agree, we don't know enough to make certain decisions, but we do know enough to know that if we continue as we are then we will cause (and have caused) climate change. What we don't know is that the measures we plan to take will be enough to reverse what we have already done.

 

It is like seeing a car rolling down a hill, it might not be going fast now, but it will pick up speed if nobody stops it, and we can't tell exactly how much force will be needed to stop it. But, we know that if no body stops it, then it will hit something at the bottom (but not necessarily what it will hit and how bad it will be - but it looks like it will cause pretty bad damage to whatever it hits).

 

Many deniers are really saying: Well the car hasn't hit anything yet, so that means it won't actually do any damage.

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JohnB    709

Sorry for the delay, but RL got in the way.

 

First up. swansont you had questions about the provenence of this graph.

scafetta_model_updated-fig-02_02_2012.png

 

The graph is drawn from Dr Scafettas paper "Testing an astronomically based decadal-scale empirical harmonic climate model versus the IPCC (2007) general circulation climate models" the original of which can be found here. The full paper is behind a paywall but if you scroll down, the figure is "Figure 5a" in the paper. A more accessable version is in the SPPI pdf. The SPPI is an updated version of the paper to add in the more recent temperature readings.

 

I have to admit to some concerns here as I have no way to verify that the "update" is the same as the original peer reviewed version. The original peer reviewed article is behind the paywall and the "update" is freely available but not peer reviewed. I can only assume that if Dr Scafetta tried to pull some sort of a swifty "bait and switch" it would be jumped on rather quickly. But anyway, that is where the graph draws its data from.

 

Once you had pointed out the .2 degree offset and questioned it, I was concerned. I hadn't noticed the point and agree it was odd. The answer is in the SPPI document in Figure 9. The graph above stats at 2000, whereas Figure 9 goes back to 1995. A common practice in climate science when using temperatures is to use a 5 year running mean. Given the 1998 El Nino and the large drop from that in 1999, I'm willing to bet that the 5 year mean runs through the .4 mark and aligns with the projection stating points. This isn't explicitly stated in the paper (which I think is a small flaw, I like to see everything laid out including the "obvious") but I think is a reasonable assumption. If the intent of a paper is to compare projections with reality then it makes no sense not to have things starting at the same point. Also using a 60 month running mean gets away from the "Starting year" problem.

 

What graph in the report is being used here? It's a big report, and the projection I find (fig 3.2 in the synthesis report, p. 46) shows multiple individual scenarios that all start at a temperature anomaly of about 0.25 ºC, which is the value for the year 2000. So it's curious that the anomaly graphed here starts at about 0.45 ºC. Why would you start your projections two tenths of a degree above the actual temperature? In the IPCC projection graph, the high temperature anomaly is at or below about 0.8 ºC in 2020, whereas here it's literally off the charts. In 2010 the high value is about 0.6 ºC, but this graph shows it as 0.8 ºC. In other words it looks to me like the projection graph has been shifted up 0.2 ºC in this graph, relative to the one I find in the IPCC AR4 report.

 

Now I'm getting confused. Looking at the IPCC AR4 WG1 Figure 3.1 (It is a bloody big report, isn't it? :D ) the temp anomalies are definitely in the .4 range and not the .2 around the year 2000.

figure3-1-l.png

 

Where is the problem? Using the running mean there is no "offset" of .2 degrees and the IPCC report itself shows that a starting point of a .4 degree anomaly is quite reasonable.

 

Now as to A1B scenarios.

 

The A1B scenario was originally defined in the TAR and can be found here. It's the BAU scenario that assumes an increasing world population up to about 2050 and then a slow decline as birthrates drop in developing nations that become developed. It also assumes a "balanced" mix of power sources with a gradual move over to wind, solar etc. If you were a betting man, then this would be called the "most likely" scenario. No magical changes in human behaviour and economics and no new magical energy devices.

 

What a lot of people don't realise is that the inputs for the climate models are actually outputs from economic models. The economic models model the world economiy for the next 100 years and from this is derived the CO2 output etc and these values are the ones the climate modellers have to use as inputs. I can't speak for others, but using the output of economic models as the input for the climate ones does not give me "high confidence" in the result. While I have some doubts about climate models 100 years out, I have very grave doubts about economic ones 100 years out.

 

So there is nothing "agressive" in the A1B scenario, it's just the BAU with humans pretty much being humans. The other thing is that the A1B is the one that people have been quoting as "what will happen" so that's the one that needs to be examined against reality. Both inputs and outputs. Put bluntly, if reality is pretty much matching the inputs, but the outputs aren't matching reality, then we should be able to agree that there is something wrong with the model and how it is handling the inputs. There is no point looking at the B2 curves and saying "Oh looky, the temps match quite well!" because the input factors don't. (Unless there has been a very large scale change to renewables and I missed it)

 

This is why the A1B scenario is the correct one to compare to reality to see if the models are getting it right. As the data shows, they aren't. If anything they are running closest to the "Commitment" curve Essay gave in post #150, but we can't compare to that curve because it assumes no increase in CO2 since 2000. Also that diagram in Dr Dennings presentation needs revision. The comparison of projections to actual temps is only for 2000-2005, it's 2012 now and another 6 years of data are available.

 

Essay.

For the sun, this "assumption" of nearly constant activity (within the limits of sunspot cycles) is detailed in the IPCC reports. Please note that models such as this are to indicate long-term trends, which is why the recent hiccup in the sunspot cycle shouldn't affect the long-term results (but may affect short term observations).

 

We did discuss this before. The IPCC assumes a change of only .5W/m-2 between a "Maunder Minimum" and the "Solar Maximum" of the 20th century. I have previously pointed out that this conclusion is based on one paper and is in opposition to all previous papers and works on this. I have also pointed out that the person responsible for choosing the paper which the IPCC relies on for its values is a co-author of the paper. (I know, that means nothing because climate scientists are of a higher moral standard than everybody else and things like "Conflict of Interest" don't apply to them) However if the worst predictions for the next cycle are bourne out and it turns into a full blown "Minima" we will be able to see which proxy values were correct. If the TSI drops by .5W/m-2 then the IPCC values are correct, if it drops by 2 w/m-2 then the IPCC values are crap and their attribution values similarly useless and the entire Northern Hemisphere is in for a shedload of trouble.

 

It won't bother us much Downunder, but you blokes will be back to 20 foot snowfalls and "Ice Fairs" on the Thames, long winters and crop failures.

 

Edtharan;

If the Earth retains energy in the form of infra-red radiation, then this will act as a warming effect (among other things).

 

From this we can conclude that CO2 is not "climate benign", so your argument that it could be, must be false. More so, it shows that there will be increases in temperatures due to an increase in CO2, but also, as this IR radiation can deliver energy into the system (usually through local warming rather than global warming), this increase in energy within the Earth's climate systems can lead to disruptions of those systems.

 

Even if we granted that all warming since 1850 was due to CO2, how can you not call it benign? The Little Ice Age was a more "benign" climate than todays? Really?

 

Actually the "unexpected" polar ice melting was unexpected in climate change denier circles. For a long time they have been saying that there won't be any increase in polar melting. Interestingly, now that it has occurred, and occurred slightly faster and in greater amounts than the lowest predictions of climate scientists, they are claiming that because deniers cherry picked models that didn't predict this amount of melting got it wrong, then climate change must be wrong.

 

Actually we expected it. We "deniers" have very funny ideas like "If the planet warms, ice will melt". And don't go the "lowest prediction" path. It was your side that was predicting an "ice free" north pole next year. It hasn't gone as fast as the predictions said it would. The biggest problem with using Arctic ice is the lack of long term data. The best we have are the satellites and they only go back to 1979 or so. Not a really good baseline for extrapolation. We don't know with any accuracy how fast the floating ice has melted in previous warmings. Heck, all you have to do is keep a close eye on ice extent and watch hundreds of thousands of square kilometres of ice appear and disappear overnight.

 

It's a warming world. Ice melts. Glaciers recede. These things happen in a warming world regardless of the cause. Glaciers have been receding since the 1700s in the Alps. Archaeology shows us that they have done so at least 7 times in the last 2,500 years.

 

The real difference is that we deniers don't start our temperature graph at the coldest point in 8,000 years and go screaming "Oh God! It's warming! We're all going to die!" Are people expected to panic every year when winter turns into spring?

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Essay    87
re: "...which is why the recent hiccup in the sunspot cycle shouldn't affect the long-term results...." ~SA

Essay.

We did discuss this before. The IPCC assumes a change of only .5W/m-2 between a "Maunder Minimum" and the "Solar Maximum" of the 20th century. I have previously pointed out that this conclusion is based on one paper and is in opposition to all previous papers and works on this. I have also pointed out that the person responsible for choosing the paper which the IPCC relies on for its values is a co-author of the paper. (I know, that means nothing because climate scientists are of a higher moral standard than everybody else and things like "Conflict of Interest" don't apply to them) However if the worst predictions for the next cycle are bourne out and it turns into a full blown "Minima" we will be able to see which proxy values were correct. If the TSI drops by .5W/m-2 then the IPCC values are correct, if it drops by 2 w/m-2 then the IPCC values are crap and their attribution values similarly useless and the entire Northern Hemisphere is in for a shedload of trouble.

"...if it drops by 2 w/m-2 then...." ~JohnB, 2Watts! John, where are you getting numbers like that from?!?

 

 

JohnB,

We talked about how a small forcing, of long duration, changes climate noticeably.

 

I recall pointing out how a change (in the solar constant) of about 0.5 W/m^2 in solar forcing, over several hundred years, was calculated to have occurred between the Medieval Warm Period and the Little IceAge; and how it was associated with that change in climate.

 

I may have cited one paper to show that point, which iirc you pointed out, but that paper was based on numerous other studies (a meta analysis of records & proxies) of solar activity during that period; wasn't it? Maybe I'm recalling something else....

Well whatever, certainly the IPCC assessment of solar insolation and variability is based on more than one paper; isn't it?

===

 

Notice also (below) the first two points:

Compared with the solar changes, greenhouse forcing has over an order of magnitude greater effect.

 

....from the: Summary for Policymakers, Fourth IPCC Report (2007)

 

http://www.ipcc.ch/p...ar4-wg1-spm.pdf

 

* The combined radiative forcing due to increases in carbon dioxide, methane, and nitrous oxide is +2.30 [+2.07 to +2.53] W m–2, and its rate of increase during the industrial era is very likely to have been unprecedented in more than 10,000 years (see Figures SPM.1 and SPM.2). The carbon dioxide radiative forcing increased by 20% from 1995 to 2005, the largest change for any decade in at least the last 200 years. {2.3, 6.4}

....

 

* Changes in solar irradiance since 1750 are estimated to cause a radiative forcing of +0.12 [+0.06 to +0.30] W m–2, which is less than half the estimate given in the TAR. {2.7}

===

 

http://www.ipcc.ch/p...en/ch9s9-2.html

 

This section briefly summarises the understanding of radiative forcing based on the assessment in Chapter 2, and of the climate response to forcing. Uncertainties in the forcing and estimates of climate response, and their implications for understanding and attributing climate change are also discussed. The discussion of radiative forcing focuses primarily on the period since 1750, with a brief reference to periods in the more distant past that are also assessed in the chapter, such as the last millennium, the Last Glacial Maximum and the mid-Holocene.

 

...and so, re: Chapter 2

http://www.ipcc.ch/p...s2-7.html#2-7-1

 

2.7.1 Solar Variability

The estimates of long-term solar irradiance changes used in the TAR (e.g., Hoyt and Schatten, 1993; Lean et al., 1995) have been revised downwards, based on new studies indicating that bright solar faculae likely contributed a smaller irradiance increase since the Maunder Minimum than was originally suggested by the range of brightness in Sun-like stars (Hall and Lockwood, 2004; M. Wang et al., 2005). However, empirical results since the TAR have strengthened the evidence for solar forcing of climate change by identifying detectable tropospheric changes associated with solar variability, including during the solar cycle (Section 9.2; van Loon and Shea, 2000; Douglass and Clader, 2002; Gleisner and Thejll, 2003; Haigh, 2003; Stott et al., 2003; White et al., 2003; Coughlin and Tung, 2004; Labitzke, 2004; Crooks and Gray, 2005). The most likely mechanism is considered to be some combination of direct forcing by changes in total solar irradiance, and indirect effects of ultraviolet (UV) radiation on the stratosphere. Least certain, and under ongoing debate as discussed in the TAR, are indirect effects induced by galactic cosmic rays (e.g., Marsh and Svensmark, 2000a,b; Kristjánsson et al., 2002; Sun and Bradley, 2002).

 

It looks as if they use more than one paper; and fairly current stuff too.

 

How many papers is this "Harmonic Component" suggestion based upon?

1. Scafetta, N.

2. ? (...i'm sure there are more, but could you point me to a link or review; thanks)

 

But whatever you say about solar influences, at least they vary; they come and go, and wax and wane over the decades and centuries. CO2 will always be "on" --Watt after extra Watt-- from pole to pole, 24/7/365, for many centuries to come. So we need to reduce CO2.

 

And y'know John, even if they are wrong, and if you doubled the solar changes, then the drift in the solar constant would still be dwarfed by the CO2 forcing. Greenhouse gas forcing is 10 to 20 times stronger than forcing from the long-term solar influence .

 

~ :)

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swansont    6167

Sorry for the delay, but RL got in the way.

 

First up. swansont you had questions about the provenence of this graph.

scafetta_model_updated-fig-02_02_2012.png

 

The graph is drawn from Dr Scafettas paper "Testing an astronomically based decadal-scale empirical harmonic climate model versus the IPCC (2007) general circulation climate models" the original of which can be found here. The full paper is behind a paywall but if you scroll down, the figure is "Figure 5a" in the paper. A more accessable version is in the SPPI pdf. The SPPI is an updated version of the paper to add in the more recent temperature readings.

 

I have to admit to some concerns here as I have no way to verify that the "update" is the same as the original peer reviewed version. The original peer reviewed article is behind the paywall and the "update" is freely available but not peer reviewed. I can only assume that if Dr Scafetta tried to pull some sort of a swifty "bait and switch" it would be jumped on rather quickly. But anyway, that is where the graph draws its data from.

 

Once you had pointed out the .2 degree offset and questioned it, I was concerned. I hadn't noticed the point and agree it was odd. The answer is in the SPPI document in Figure 9. The graph above stats at 2000, whereas Figure 9 goes back to 1995. A common practice in climate science when using temperatures is to use a 5 year running mean. Given the 1998 El Nino and the large drop from that in 1999, I'm willing to bet that the 5 year mean runs through the .4 mark and aligns with the projection stating points. This isn't explicitly stated in the paper (which I think is a small flaw, I like to see everything laid out including the "obvious") but I think is a reasonable assumption. If the intent of a paper is to compare projections with reality then it makes no sense not to have things starting at the same point. Also using a 60 month running mean gets away from the "Starting year" problem.

 

Now I'm getting confused. Looking at the IPCC AR4 WG1 Figure 3.1 (It is a bloody big report, isn't it? :D ) the temp anomalies are definitely in the .4 range and not the .2 around the year 2000.

figure3-1-l.png

 

Where is the problem? Using the running mean there is no "offset" of .2 degrees and the IPCC report itself shows that a starting point of a .4 degree anomaly is quite reasonable.

 

The graph is quite like fig 8 in the linked pdf, and the legend says it's the surface temperature, so it's not averaged. (There is also a "4-year smooth" curve, which is not reproduced in the graphs that are posted in the thread)

 

If you scroll up to fig 7, you see the IPCC graph, and the year-2000 value is slightly below 0.2 ºC — there's even a line on the graph extending to the right axis to show this. That's where the projections start. (Other graphs may use a different baseline value for 0º; since these are relative values, you can't mix-and-match without normalizing to the same baseline.)

 

In fig 9, the "average" is his model.

 

So as far as I can tell we still have an issue of Scafetta's graphs not matching up at year 2000, giving an illusion of a (larger) difference for the projections as compared to actual.

 

 

Now as to A1B scenarios.

 

The A1B scenario was originally defined in the TAR and can be found here. It's the BAU scenario that assumes an increasing world population up to about 2050 and then a slow decline as birthrates drop in developing nations that become developed. It also assumes a "balanced" mix of power sources with a gradual move over to wind, solar etc. If you were a betting man, then this would be called the "most likely" scenario. No magical changes in human behaviour and economics and no new magical energy devices.

 

What a lot of people don't realise is that the inputs for the climate models are actually outputs from economic models. The economic models model the world economiy for the next 100 years and from this is derived the CO2 output etc and these values are the ones the climate modellers have to use as inputs. I can't speak for others, but using the output of economic models as the input for the climate ones does not give me "high confidence" in the result. While I have some doubts about climate models 100 years out, I have very grave doubts about economic ones 100 years out.

 

So there is nothing "agressive" in the A1B scenario, it's just the BAU with humans pretty much being humans. The other thing is that the A1B is the one that people have been quoting as "what will happen" so that's the one that needs to be examined against reality. Both inputs and outputs. Put bluntly, if reality is pretty much matching the inputs, but the outputs aren't matching reality, then we should be able to agree that there is something wrong with the model and how it is handling the inputs. There is no point looking at the B2 curves and saying "Oh looky, the temps match quite well!" because the input factors don't. (Unless there has been a very large scale change to renewables and I missed it)

 

This is why the A1B scenario is the correct one to compare to reality to see if the models are getting it right. As the data shows, they aren't. If anything they are running closest to the "Commitment" curve Essay gave in post #150, but we can't compare to that curve because it assumes no increase in CO2 since 2000. Also that diagram in Dr Dennings presentation needs revision. The comparison of projections to actual temps is only for 2000-2005, it's 2012 now and another 6 years of data are available.

 

This is all (or mostly) moot if the projection offset is not corrected.

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waitforufo    107
Stated briefly, I will simply try to clarify what the debate over climate change is really about. It most certainly is not about whether climate is changing: it always is. It is not about whether CO2 is increasing: it clearly is. It is not about whether the increase in CO2, by itself, will lead to some warming: it should. The debate is simply over the matter of how much warming the increase in CO2 can lead to, and the connection of such warming to the innumerable claimed catastrophes. The evidence is that the increase in CO2 will lead to very little warming, and that the connection of this minimal warming (or even significant warming) to the purported catastrophes is also minimal. The arguments on which the catastrophic claims are made are extremely weak – and commonly acknowledged as such. They are sometimes overtly dishonest. --Professor Richard Lindzen MIT, Atmospheric Physicists, Before the House of Commons Feb 22, 2012

 

Doesn't sound like a crisis to me.

 

Read more about it at..

 

http://blogs.independent.co.uk/2012/02/22/is-catastrophic-global-warming-like-the-millenium-bug-a-mistake/

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swansont    6167

 

No, it's clear from the writing that it's meant not to. But there's a problem with the link — the site has no actual science presented.

 

If Lindzen is right

 

The issue is whether you can remove the "if" from in front of that sentence.

 

Also, the tie-in with the millennium bug is curious. You can't say it wasn't a potential problem because we actually expended effort fixing it. This was a one-off event. It's not like e.g. vaccines, where we can actually see that spending money on them has an effect because of the recent antiscience effort resulting in fewer people getting them, and the resultant increase in diseases.

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JohnB    709

swansont.

The graph is quite like fig 8 in the linked pdf, and the legend says it's the surface temperature, so it's not averaged.

 

The temperature data is the HADCRUT3 dataset and is a global average. http://www.cru.uea.ac.uk/cru/data/temperature/hadcrut3gl.txt

 

(There is also a "4-year smooth" curve, which is not reproduced in the graphs that are posted in the thread)

 

I went for 5 year, but that is why the temps don't appear to line up with the .4 degree mark. The raw don't, but the average does.

 

If you scroll up to fig 7, you see the IPCC graph, and the year-2000 value is slightly below 0.2 ºC — there's even a line on the graph extending to the right axis to show this. That's where the projections start. (Other graphs may use a different baseline value for 0º; since these are relative values, you can't mix-and-match without normalizing to the same baseline.)

 

I agree about Figure 7 but think it's a pretty crappy figure from the IPCC, not very detailed at all. Consider Figure 6 which is IPCC’s figures 9.5a and 9.5b that show the global anomaly in 2000 to be around .4 degrees. In figure 2 we see exactly the same thing with the HADCRUT data showing the anomaly in 2000 to be .4 degrees.

 

So there is no "offset". The temperature series show the anomaly in 2000 to be .4 degrees. The starting point for all the model runs is .4 degrees in 2000. All the models and temperature series are normalised to the same point, a .4 degree anomaly in the year 2000. Right now the model projections aren't doing very well and it's going to take about a .4 degree increase in average temps between now and 2020 to match the projections and that is looking less and less likely every day.

 

Essay,

"...if it drops by 2 w/m-2 then...." ~JohnB, 2Watts! John, where are you getting numbers like that from?!?

 

Gee, I don't know, maybe all the papers that put the difference between the Maunder Minimum and now at between 3 and 10 W/m-2.

 

I recall pointing out how a change (in the solar constant) of about 0.5 W/m^2 in solar forcing, over several hundred years, was calculated to have occurred between the Medieval Warm Period and the Little IceAge; and how it was associated with that change in climate.

 

I may have cited one paper to show that point, which iirc you pointed out, but that paper was based on numerous other studies (a meta analysis of records & proxies) of solar activity during that period; wasn't it? Maybe I'm recalling something else....

Well whatever, certainly the IPCC assessment of solar insolation and variability is based on more than one paper; isn't it?

 

Yes, on only one paper. The paper being WAng et al 2005 coauthored by Judith Lean, who also just happened to be the only Solar person in the IPCC author group who was conversant on solar forcings. People choosing their own papers to quote is why out in the real world we have things called "Conflict of Interest" policies. The IPCC has them, they are just ignored as being too hard. Tough.

 

If you go down the page to the thread "Who here is a Global Warming Sceptic" http://www.scienceforums.net/topic/57883-who-here-is-a-global-warming-skeptic/page__st__40

 

Go to page 3 and you'll find where I dug out all the papers referenced by the IPCC for solar forcings and showed that the majority put the change in TSI between the Maunder Minimum and the late 20th Century at between 3 and 10 W/M-2. Only one paper put the figure at .5 W/m-2 and that was the one chosen as representative. On page 2 of that thread you can see the values for these papers as quoted by the IPCC in the graph you supplied. Take some time and compare what the IPCC says the values were in the referenced papers and what the values really were.

 

One thing I do find interesting is that most people don't have a real problem with the "Faint Sun Paradox" and are quite happy to accept that the Suns output long ago was possibly 200W/m-2 less than it is today but at the same time find it impossible to think that the Sun could vary by 3 W/m-2 between a Grand Minima and a Grand Maxima.

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Essay    87

One thing I do find interesting is that most people don't have a real problem with the "Faint Sun Paradox" and are quite happy to accept that the Suns output long ago was possibly 200W/m-2 less than it is today but at the same time find it impossible to think that the Sun could vary by 3 W/m-2 between a Grand Minima and a Grand Maxima.

...Are you talking about the "faint sun" from billions of years ago, and suggesting that should compare with variation over some recent centuries?!? [Maybe that is just "most people" whom you know.]

===

 

 

...[re: the 0.5 Watt/m^2 claim....]

Essay,

Gee, I don't know, maybe all the papers that put the difference between the Maunder Minimum and now at between 3 and 10 W/m-2.

...John, is that "total forcing" or forcing only from "solar insolation" between then and now? [see below also*] ...Can you share (or at least cite) all those papers?

===

 

 

...[re: the IPCC graph on solar forcing...]

Yes, on only one paper. The paper being WAng et al 2005 coauthored by Judith Lean, who also just happened to be the only Solar person in the IPCC author group who was conversant on solar forcings. People choosing their own papers to quote is why out in the real world we have things called "Conflict of Interest" policies. The IPCC has them, they are just ignored as being too hard. Tough.

 

If you go down the page to the thread "Who here is a Global Warming Sceptic" http://www.sciencefo...ic/page__st__40

 

Go to page 3 and you'll find where I dug out all the papers referenced by the IPCC for solar forcings and showed that the majority put the change in TSI between the Maunder Minimum and the late 20th Century at between 3 and 10 W/M-2. Only one paper put the figure at .5 W/m-2 and that was the one chosen as representative. On page 2 of that thread you can see the values for these papers as quoted by the IPCC in the graph you supplied. Take some time and compare what the IPCC says the values were in the referenced papers and what the values really were.

...so are you saying the graph doesn't portray "what the values really were?" That is an extraordinary claim! But....

 

 

*John, you're right! We had this conversation before.

JohnB, on 24 June 2011 - 08:37 AM, said:

Essay, how do you arrive at that figure? The difference between the LIA and today is listed by the IPCC as 2.4 w/sq.metre. Assuming the MWP was of similar temp ranges as today one would expect the forcing value to be similar. *Again, is that total forcing or just the solar component?

...from:

 

http://www.sciencefo...post__p__613805

 

The graph (as I recalled) is a compilation of many studies, not data from one author as you have suggested twice now. I'm just going by the graph, but am I not reading it right--about it being a meta analysis or at least a compilation of many other studies?

 

post-47272-0-38853600-1330370856_thumb.png

 

 

full graph at:

http://www.ipcc.ch/p...igure-6-13.html

 

Also, speaking of not reading the graph correctly: Do you agree that--whether it is wrong or not--this graph shows about a half Watt of change between the MWP & LIA (or 1150 v. 1450)?

In that post from June, 2011 (and the posts above), I keep saying "between the LIA & MWP," whereas you keep saying "between the Maunder Minimum & Today;" but either way the graph backs up my numbers--if I'm reading it right--of about a half Watt change in average forcing from drifting solar activity (minimum difference) ...though (to be fair, it is) slightly over 1.0 Watt/m^2 if you look at the maximum difference (GRT 2005 -or- AJS 2006). However, the "average" [black line] of the various studies is still at about a half Watt difference; isn't it?

===

 

 

Back then, I recall you picked numbers from two solar cycles that were centuries apart and subtracted them to get those answers of from 3 to 10 Watts/m^2....

on June 26, 2011, JohnB said: I have trouble matching that with Figure 1A which clearly shows the SI at 1368 W/M-2 up from a baseline of 1365 W/M-2. Similarly in 1700 the Solar figure goes down to 1362 W/M-2. This is a range of 6 W/M-2, not .6 W/M-2.
...but I still don't think that is a valid way to compare solar activity between any different periods or between then and now. Do you?

 

 

~blink.gif

Edited by Essay

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swansont    6167

swansont.

 

 

The temperature data is the HADCRUT3 dataset and is a global average. http://www.cru.uea.ac.uk/cru/data/temperature/hadcrut3gl.txt

 

The issue was whether it was a temporal average, and it isn't.

 

 

I went for 5 year, but that is why the temps don't appear to line up with the .4 degree mark. The raw don't, but the average does.

 

 

I agree about Figure 7 but think it's a pretty crappy figure from the IPCC, not very detailed at all. Consider Figure 6 which is IPCC’s figures 9.5a and 9.5b that show the global anomaly in 2000 to be around .4 degrees. In figure 2 we see exactly the same thing with the HADCRUT data showing the anomaly in 2000 to be .4 degrees.

 

One graph I saw earlier uses 1960-1980 as the zero temperature. Figure 7 is relative to 1980–1999, which gives it a smaller year 2000 offset. Fig 6 is relative to the period 1901 to 1950 (you can see this if you click through in the pdf to the IPCC report and read the text). You CAN'T just mix-and-match these without adjusting for the different baselines.

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JohnB    709
...Are you talking about the "faint sun" from billions of years ago, and suggesting that should compare with variation over some recent centuries?!? [Maybe that is just "most people" whom you know.]

 

Well you have a problem with it for a start.

 

...John, is that "total forcing" or forcing only from "solar insolation" between then and now? [see below also*] ...Can you share (or at least cite) all those papers?

 

I did last time but they obviously weren't read. That's why I pointed to the previous thread, to try and save myself from doing the same work over again.

 

...so are you saying the graph doesn't portray "what the values really were?" That is an extraordinary claim! But....
Also, speaking of not reading the graph correctly: Do you agree that--whether it is wrong or not--this graph shows about a half Watt of change between the MWP & LIA (or 1150 v. 1450)?

In that post from June, 2011 (and the posts above), I keep saying "between the LIA & MWP," whereas you keep saying "between the Maunder Minimum & Today;" but either way the graph backs up my numbers--if I'm reading it right--of about a half Watt change in average forcing from drifting solar activity (minimum difference) ...though (to be fair, it is) slightly over 1.0 Watt/m^2 if you look at the maximum difference (GRT 2005 -or- AJS 2006). However, the "average" [black line] of the various studies is still at about a half Watt difference; isn't it?

 

I'll take these and the graph in the one hit. And for the record, yes the graph does indeed show about a .5W/m-2 change in solar insolation between the LIA and now. That is exactly why I say it misrepresents the papers. I said it last time and linked directly to the damn papers so that anybody could actually go and look for themselves.

 

But here it all is again. The papers used to create the IPCC graph linked to as Figure 6.13 can be found as a list in Table 6.2.

 

González-Rouco et al., 2003 http://w3k.gkss.de/staff/storch/pdf/gonzalez.et.al.2003.soil.pdf

Osborn et al., 2006 http://coast.gkss.de/G/Mitarbeiter/storch/pdf/osborn.magicc-echog.2006.pdf

Tett et al., 2007 http://www.springerlink.com/content/xg6116h0t30g26g2/

Mann et al., 2005b http://journals.ametsoc.org/doi/full/10.1175/JCLI3564.1

Bertrand et al., 2002b http://onlinelibrary.wiley.com/doi/10.1034/j.1600-0870.2002.00287.x/pdf

Crowley et al., 2003 http://www.sages.ac.uk/home/homes/ghegerl/Crowley.2003GL017801.pdf

Goosse et al., 2005b http://coast.hzg.de/staff/zorita/ABSTRACTS/GoosseXetalGRL2005.pdf

Gerber et al., 2003 http://www.meteo.psu.edu/~mann/shared/articles/GerberClimDyn03.pdf

Bauer et al., 2003 http://www.mpimet.mpg.de/fileadmin/staff/claussenmartin/publications/bauer_al_1000_grl_03.pdf

González-Rouco et al., 2006 http://esrc.stfx.ca/pdf/2005GL024693.pdf

Stendel et al., 2006 http://www.gps.caltech.edu/~vijay/EGU%20Presentations/Climate%20Change/Stendel-etal-06.pdf

 

11 papers.

González-Rouco et al., 2003 is a temp reconstruction using borehole data. No great help regarding TSI.

Osbourne et al 2006 is a comparison of model runs and inspects why Erik in the ECHO-G models is an outlier.

Tett et al 2007 is another climate model run and is behind a paywall, making it hard to check the values.

Mann et al 2005b is on the reliability of dendrothermometry in paleoclimate reconstructions. Nothing there on TSI.

 

Bertrand et al 2002b Finally something on TSI. Bertrand is a series of model rund using a variety of forcings. I direct you to Figure 1. While the Be10 series from Crowley is quite stable and closely matches the IPCC preferred .5W/m-2, the Reid reconstruction shows a variance of nearly 20 W/m-2 between 1450 and today. Of the three values used in Bertrand, only the one that bolsters the IPCC opinion is used in their graph. I believe this is called "Cherry picking".

 

Crowley et al 2003 is concerned with modelling ocean heat content over the last 1,000 years.

Goosse et al 2005b looks at the differences between accepted forcings used in climate model that have hindcast the last 1,000 years or so. Please note Figure 1a "Time variations of solar irradiance at the top of the atmosphere" from a series of reconstructions. While not closely agreeing all the reconstructions place the TSI change between circa 1500 and 2000 in a range from 2W/m-2 to 6W/m-2. Maybe if you squint really hard you can squash it down to .5W/m-2.

 

Gerber et al 2003. Sorry, but this is just a piss poor paper. Reids 20 W/m-2 has been "smoothed" to a 1 W/m-2 change, but there is a story to tell I suppose. I especially like this part;

For example, the role of solar variability for climate change has been discussed controversially (Ramaswamy et al. 2001).

Ramaswamy et al 2001 is IPCC TAR WG1. How pathetically sloppy, it's like listing "Encyclopedia Brittanica Volume 6" as a reference.

 

Bauer et al 2003 Two TSI reconstructions are shown in figure 1. One is for a change of around 4W/m-2 and the other is a change of about 6W/m-2.

 

González-Rouco et al., 2006 is another bore hole temperature series.

 

Stendel et al., 2006 A more interesting paper with Figure 1 putting the change at around 4W/m-2 between 1500 and 2000.

 

Gee, are you starting to see where I got the 2W/m-2 guesstimate from yet? But I'm not finished.

 

Hoyt and Schattern 1993 http://www.leif.org/EOS/93JA01944.pdf Figure 9 is the one you want here. A composite of model simulations showing the TSI going from 1367W/m-2 in 1700 to about 1372 today, a change of 5 W/m-2.

 

Lean et al 1995 http://www.geo.umass.edu/faculty/bradley/lean1995.pdf Unfortunately the correlation technique bottoms out when sunspots reduce to zero and so this reconstruction only shows a change of 3-4 W/m-2 from the LIA to today. However it is far more likely that the TSI dropped below the 1364 W/m-2 figure during the hundred year minima.

 

Bard et al 2000 ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/solar_variability/bard_irradiance.txt Just scroll down the figures and you'll see variations of more than 4 W/m-2.

 

The paper used by the IPCC to decide that the change was only .5W/m-2 and not the higher figures was this one, M. Wang et al., 2005. I'm sure that the fact that the only qualified solar person doing this bit of AR4 just happened to be a coauthor of the paper had nothing to do with it. The thing is of course that Wang could be right and the others wrong, but it takes more ethical behaviour than "Trust me, I'm a scientist" to prove it. The selection process for the choosing the paper stinks of "Conflict of Interest".

 

The bottom line here is that .5W/m-2 fits the narrative and higher values don't. If you want people to buy your story then you have to make sure they only hear some of the facts. Remember that the IPCC is an Intergovernmental panel and not a scientific one. Its purpose is to provide reports consistent with desired policy outcomes and not reality. This is not to disparage the many fine people who are involved, byt they can write whatever they want, the summaries are written by the political animals and they are the bits that count.

 

A quick proceedural question. Do you write a summary to reflect the facts of a report or do you write the summary and then edit the main report to match the summary? Which does the IPCC do?

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JohnB    709

Essay, I have to also ask a logical question. You are quite happy with the idea that TSI changes by about 1.4 W/m-2 during the 11 year cycle. You've used that figure in previous posts and I don't have a problem with it.

 

However, if we look at the actual cycles;

sunspot_yearly.gif

 

We can reasonably say that 3 of the last 5 cycles peaked out at 150. This gives a median figure of 75 for the cycles and a logical problem with the whole .5W/m-2 from the LIA to now. If the TSI varies by 1.4 W/m-2 over a cycle then it can be fairly said to vary by .7W/m-2 either side of the median. So the drop from median to minima in a given cycle, a drop from 75 spots to zero gives a reduction of .7W/m-2.

 

If this is true, then how can the claim be made that to drop the median from 75 to zero, as we see in a prolonged minima, only result in a .5W/m-2 drop in forcing?

 

75 to zero in 5.5 years, a half cycle, results in a .7W/m-2 drop in TSI but a 75 to zero drop and staying at zero for 100 years only gives a .5W/m-2 drop in TSI? You are arguing that a short drop to a lower level of sunspot activity gives a greater reduction in TSI than a prolonged drop to the same level.

 

This makes no sense.

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