Global Warming re-derived?

[iNow]

Hansen also published a later paper which did not suffer those faults.

 

Others also published papers without those faults, but which arrived at the same conclusion.

 

What point exactly are you trying to make? You realize that ONE paper is now 20 years old, right?

 

 

This same tired argument has already been defeated. Don't you have anything new to offer?

 

http://www.scienceforums.net/forum/showthread.php?p=370604&highlight=hansen#post370604

[Reaper]

I'm glad you asked! James Hansen's (NASA GISS) predictions from 1987 (published in an 1988 paper) are quite illuminating. They were, in fact, used for the basis of the IPCC's first assessment report, and this paper (along with Hansen's later works are still heavily cited today):

 

He calculated three scenarios. Scenario A assumed continued growth of CO2 emissions at current levels -- this is in fact very close to what has happened in the 21 years since he made those predictions. And what was the calculated temperature rise by 2008? A full 1.0C above the 1951-1980 mean. What did temperatures actually rise? As of last month, they're 0.2C. Warming was overpredicted by 500%.

 

The *coolest* of the 3 was based on the assumptions that the world would stabilize CO2 emissions by the year 2000. Even for that scenario, Hansen predicts a warming of 0.62C by 2008. But -- even though emissions have continued nearly unrestrained, warming has only been a tiny fraction of that.

 

The facts are clear. Models predictions from the 1980s and 1990s were hugely overstated. People who claim the "models predicted less warming than we've seen" are wrong, plain and simple.

 

 

Really? Then take one good look at the papers here:

 

 

 

This doesn't look like it supports your assertion at all. In fact, it looks like you were just cherry picking and making things up (nor does it seem like you know how to calculate a standard deviation...)

 

Also, read this thread: http://www.scienceforums.net/forum/showthread.php?t=27104. Your analysis is wayyyyyy off.

[ecoli]

what are the 3 scenarios, Reaper?

[Reaper]

what are the 3 scenarios, Reaper?

 

 

They are listed right on the graphs; all they basically are is just a set of predictions on how the Earth might end up warming over time. The reason I brought this up is because what is displayed on the graphs (with the second one showing the observed increases) contradicts his claim that "warming was overpredicted by 500%". Also, the figures he pulled out were clearly cherry picked (e.g. the .2 C increase this poster was talking about, was a reference to the fact that warming had been occurring at .2 C per decade on average).

[JohnB]

ttowntom, the comment you are referring to was by Bascule, not inow.

 

There is a logical dissonance here.

 

Swansont asked: "What were the predictions that were made in 1980? 1970? Did they under- or overpredict the warming we've seen in the last 30-40 years?"

 

ttowntom supplied Hansen 1988 which would reasonably qualify as being from the period and making predictions. (Which BTW over-predicted the warming.)

 

inow comments: "You realize that ONE paper is now 20 years old, right?"

 

I would have thought that any paper making predictions in the 70s or 80s would be 20-30 years old by now.

 

Let's add in:"Historical predictions were not made with the same models, and 10 years is a relatively short timescale over which to make comparisons." (Which is, to a certain extent true.)

 

So, we shouldn't look at the predictions of the old models because they were different and, well, old, so they don't count and we shouldn't look at the new models because there hasn't been enough time to make comparisons.

 

I thought the whole point of the scientific method was to create models and make predictions that could be tested.

[ttowntom]

This doesn't look like it supports your assertion at all.

Only to those unable to read a simple line graph.

 

You realize that ONE paper is now 20 years old, right?

This is really getting ludicrous. I show you 10-year old predictions and you say that's not long enough to judge. I point out 20-year old predictions and you imply they're too old?

 

The point stands. No GCM prediction has ever been close to being accurate. The latest IPCC estimates in 2007 scaled back warming estimates dramatically (down to about a 3C sensitivity), and they're still overstating warming by 30-50%.

 

And btw, this is more than just "one paper". It's the official prediction of NASA's GISS, published in multiple papers, several books, thousands of media reports, and at least two testimonies before Congress.

 

ttowntom, the comment you are referring to was by Bascule, not inow.

Ah, you are right. My apologies to misattributing iNow.

[iNow]

The point stands. No GCM prediction has ever been close to being accurate.

Not quite. You've just attempted to sweep aside decades of research with a single sentence, and you have not yet referenced which models to which you're referring.

 

 

The latest IPCC estimates in 2007 scaled back warming estimates dramatically (down to about a 3C sensitivity), and they're still overstating warming by 30-50%.

So, now you're suggesting that the IPCC is incompetent because they revise their estimates in the face of new information?

 

Super approach there, champ.

 

 

And btw, this is more than just "one paper". It's the official prediction of NASA's GISS, published in multiple papers, several books, thousands of media reports, and at least two testimonies before Congress.

Show us precisely which part is in err.

[ttowntom]

So, now you're suggesting that the IPCC is incompetent because they revise their estimates in the face of new information?

I said no such thing, and don't try to change the subject. The fact that the IPCC has had to repeatedly lower their assessments proves the point. Predictions of global warming have perpetually and dramatically overstated the degree of actual warming experienced. Simple, unequivocal truth.

 

The blind fervor with which you defend your faith might be admirable in, say a Catholic bishop or an Islamic mullah. But it has no place in scientific debate.

[Reaper]

Only to those unable to read a simple line graph.

 

Whoa! Did this guy just fail statistical analysis class?

 

This is really getting ludicrous. I show you 10-year old predictions and you say that's not long enough to judge. I point out 20-year old predictions and you imply they're too old?

 

You are arguing against a point that was never made? And, you haven't actually shown anything as of yet, all you did was pull out a graph with no reference to observed data and then proclaimed that you somehow debunked the climate models.

 

The point stands. No GCM prediction has ever been close to being accurate. The latest IPCC estimates in 2007 scaled back warming estimates dramatically (down to about a 3C sensitivity), and they're still overstating warming by 30-50%.

 

Your point doesn't stand, because you are wrong. The corrections made were minuscule. And, the margin of error is much less then 30-50%, if you actually read the link I posted in an earlier thread.

 

And btw, this is more than just "one paper". It's the official prediction of NASA's GISS, published in multiple papers, several books, thousands of media reports, and at least two testimonies before Congress.

 

Yes, and all you have done is cherry picked data points and claims and then made some other stuff up.

 

And, you have not actually backed your claims. Nowhere in these sources you "cited" does it say any of what you previously claimed.

[ecoli]

I said no such thing, and don't try to change the subject. The fact that the IPCC has had to repeatedly lower their assessments proves the point. Predictions of global warming have perpetually and dramatically overstated the degree of actual warming experienced. Simple, unequivocal truth.

 

You've been repeating this, but you haven't shown any sources showing this to be true. Where has the IPCC done this?

[JohnB]

Reaper, don't dodge. Those graphs from Hansen et al clearly show the predictions were way off.

 

From Hansen 1988;

Scenario A assumes that the growth rate of trace gas emissions typical of the 1970s and 1980s will continue indefinitely; the assumed annual growth rate averages about 1.5% of current emissions, so the net greenhouse forcing increases exponentially.

This seems the most accurate assumption, but the prediction is way off.

Scenario B has decreasing trace gas growth rates, such that the annual increase of the greenhouse climate forcing remains approximately constant at the present level.

Well that didn't happen yet the B prediction is still high.

Scenario C drastically reduces trace gas growth between 1990 and 2000 such that the greenhouse climate forcing ceases to increase after 2000.

That didn't happen either, yet Scenario C most closely matches the observed temps.

 

It's not enough that the graph comes close to the observations, the underlying assumed increases in forcings must also match the observations. Hansen 1988 fails the second part making his graph as meaningless as comparing temp rise inversely to pirates.

 

(Personally, I don't know how Hansen got away with this particular graph as he states clearly that only scenario A includes "the effect of several hypothetical or crudely estimated trace gas trends (Ozone, Stratospheric Water Vapour and minor chlorine and flourine compounds)" whereas B and C do not.

 

Seems a case of apples and oranges to me. The three scenarios should have been run as "all in" or "all out" IMO.)

[ttowntom]

You've been repeating this, but you haven't shown any sources showing this to be true. Where has the IPCC done this?

Anyone following the debate already realizes the IPCC has repeatedly scaled back predictions in each of their reports. Here's the graph from IPCC AR3 (2001), which shows a range of predictions for warming by 2100 to be between 1.4C - 5.7C:

 

 

Now contrast that with the projections graph on page 762 of AR4 (2007), which shows a range from 0.5C - 4.1C:

 

http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch10.pdf

 

Go back to the heady days of the 1990s, and you'll see many predictions with values ranging all the way up to an astonishing 10C or more! Clearly nonsense, from the paleo record if nothing else...but it didn't stop those soothsayers from getting published in peer-reviewed journals, and having thousands of credulous reporters unquestioningly repeat their nonsense.

[iNow]

Please excuse my impatience, but what the fu(k is the point of doing this all again?

 

Does someone seriously think they've found the silver bullet which pierces all of the previous research? If so, what the hell are you doing here? Go publish and win yourself a nobel...

 

 

I'm getting grumpy in my old age...

 

 

 

 

 

Here's the graph from IPCC AR3 (2001), which shows a range of predictions for warming by 2100 to be between 1.4C - 5.7C:

<...>

 

Now contrast that with the projections graph on page 762 of AR4 (2007), which shows a range from 0.5C - 4.1C:

 

And, again... you're trying to argue that they are incompetent because they IMPROVED their projections? Interesting approach you've chosen to take...

[JohnB]

I think he's trying to show that while the IPCC has revised their estimates the revision is in a downward direction and therefore the IPCC TAR estimates were too high.

 

Therefore the earlier estimates overpredicted the possible temp rise. (Which is true.)

I'm getting grumpy in my old age...

It's my birthday sunday, can I be grumpy too?

[Reaper]

It's not enough that the graph comes close to the observations, the underlying assumed increases in forcings must also match the observations. Hansen 1988 fails the second part making his graph as meaningless as comparing temp rise inversely to pirates.

 

...............................

 

Seems a case of apples and oranges to me. The three scenarios should have been run as "all in" or "all out" IMO.)

 

Oh, ok, my mistake. Thanks for making that clear. That still doesn't get ttowntom off the hook though.....

[ttowntom]

Does someone seriously think they've found the silver bullet which pierces all of the previous research?

Your mistake lies in assuming "all the previous research" said the same thing. The myth of "conensus" resurfaces again. But as anyone who regularly reads the literature knows, no such beast exists.

 

As for the idea that this is "just a single paper", there are a dozen just in the last year alone which demonstrate the role of CO2 in climate change has been drastically overestimated. In fact, the mounting pile of evidence in papers prior to March 2006 (the cutoff period for inclusion in AR4) is the entire reason for those scaled-back predictions.

 

The "piercing" has already been done. It's just not something done all at once, by a single paper. It's a continual process, which has slowly refuted those original doomsday scenarios. Is the IPCC still overpredicting warming? Almost certainly, in light of recent research...but even their existing predictions aren't all that frightening. Those still believing in doomsday have their heads in the sand.

[iNow]

So, how about you actually cite one or two?

 

 

I might decide to take you seriously if you move beyond mere hand waving.

[ttowntom]

So, how about you actually cite one or two?

A couple off the top of my head:

 

Douglass, et al (2007) International Journal of Climatology of the Royal Meteorological Society: A comparison of tropical temperature trends with model predictions

 

http://www3.interscience.wiley.com/cgi-bin/abstract/117857349/ABSTRACT?CRETRY=1&SRETRY=0

 

Schwartz, 2007, Journal of Geophysical Research: Heat Capacity, Time Constant, and Sensitivity of Earth's Climate System:

http://www.ecd.bnl.gov/steve/pubs/HeatCapacity.pdf

 

Zhen-Shan, Sun-Xian: Multi-scale analysis of global temperature changes and trend of a drop in temperature in the next 20 years:

http://www.springerlink.com/content/g28u12g2617j5021/

 

Dr. Soon from Harvard-Smithsonian had a recent paper on the same topic as well, though I can't find a non-subscription link to it atm. And of course, the Belgium Royal Meteorological Society came out last year with an official statement saying CO2's effects have been "grossly overstated".

 

And, most telling of all, is the fact that there's been no warming trend since 1998, and no statistically significant warming trend since about 1995.

 

Finally, there are plenty of peripheral papers, which don't directly address the CO2 sensitivity issue, but cast doubt on it in other manners, such as demonstrating the current warming trend began ~250 years ago (i.e. before the industrial age), or ones correlating solar activity to temperature changes, such as those by Svensmark of the Danish Space Institute, or Shaviv in Israel, and Usoskin's (the world's foremost solar physicist) recent conversion to a belief in solar-induced recent climate change.

[iNow]

A couple off the top of my head:

Okay. Thank you. So, what is the point you're trying to make about this overstatement?

 

I'll look at your papers, but perhaps you can be explicit in the position you are trying to support.

 

 

 

And, most telling of all, is the fact that there's been no warming trend since 1998, and no statistically significant warming trend since about 1995.

Now, that's just false, and your own sources refute this. Why are you lying?

 

 

Finally, there are plenty of peripheral papers, which don't directly address the CO2 sensitivity issue, but cast doubt on it in other manners, such as demonstrating the current warming trend began ~250 years ago (i.e. before the industrial age), or ones correlating solar activity to temperature changes, such as those by Svensmark of the Danish Space Institute, or Shaviv in Israel, and Usoskin's (the world's foremost solar physicist) recent conversion to a belief in solar-induced recent climate change.

 

Be specific. Which ones? Also, how do these papers do anything to refute existing knowledge regarding the impact of human contributions of CO₂ to the atmosphere? My point being that the fact that climate change may have started sooner does not negate the effect we as a culture are having on it.

[Chris C]

Hansen's scenario B (not A) turned out to be the most accurate emission scenario, and got the corresponding warming right well within the uncertainty range. RC had a post on this (http://www.realclimate.org/index.php?p=447 ). I've went back to the original paper, and I see no faults with the RC piece.

 

The citation of the first paper is just intellectual dishonesty. Another one that RC tore apart not too long ago. Personally, I'm only a few years removed from "boy who cried wolf" stories which is why I don't bother wasting my time with Christy and Soon and Baliunas and Roy Spencer, etc. Too much literature to read, not enough time for the BS.

 

The second paper should not be taken as a denialist paper. It claims that CO2 causes warming, but has a low sensitivity. The problem is the simple 1-box model used by schwartz which gives the climate one characteristic timescale to respond (i.e., he assumed that the oceans will respond as quick as land and the atmosphere). He says that it is a very simple model himself, but there is a slight irony in the blogosphere when it comes to the complicated GCM's (like the IPCC graph someone is throwing around) that all fail, but the simple models that say "not as much CO2 effect" that are now the gospel truth.

[iNow]

The citation of the first paper is just intellectual dishonesty.

 

 

The second paper should not be taken as a denialist paper.

 

<...>

 

(he assumed that the oceans will respond as quick as land and the atmosphere).

 

 

Thanks for pointing out the flaws Chris. It appears that, while the second paper is not denialist, it is based on overly simplified assumptions, some of which are non-representative of reality?

[ttowntom]

The citation of the first paper is just intellectual dishonesty. Another one that RC tore apart not too long ago.

Translation: any scientist who disagrees with the third-rate hacks who founded RC is obviously wrong -- no need to even consider their data, evidence, or arguments!

 

Must make life a lot easier than actually using that gray matter, eh?

 

Personally, I'm only a few years removed from "boy who cried wolf" stories

And I'm even further removed from the Chicken Little sky-is-falling stories, given I've been hearing them in one form or another since the 1960s.

 

there is a slight irony in the blogosphere when it comes to the complicated GCM's (like the IPCC graph someone is throwing around) that all fail, but the simple models that say "not as much CO2 effect" that are now the gospel truth.

Not nearly as ironic as taking GCMs as gospel, despite their utter lack of predictive ability, and automatically discounting any research which disagrees with their conclusions, simply because "the model says it ain't so".

 

There is no observational evidence for a climate sensitivity anywhere near what the models predict. In fact, their "predicted" sensitivity has been being lowered for decades. Eventually, they'll get it right, and stop dramatically overpredicting future warming. But for now, they're useless as predictive tools.

[iNow]

Already the substance of your posts is lacking, ttowntom, and only 3 or 4 posts in you've already degenerated into attack mode instead of support your own position mode. And... so it goes with the global climate change debate occurring across the net.

[JohnB]

Hansen's scenario B (not A) turned out to be the most accurate emission scenario.

To quote original paper;

Scenario B has decreasing trace gas growth rates, such that the annual increase of the greenhouse climate forcing remains approximately constant at the present level.

The growth rate of trace gases is decreasing? To quote the Energy Information Administration

World carbon dioxide emissions are expected to increase by 1.9 percent annually between 2001 and 2025.

Source.

 

That is the assumption for Scenario A, not B. Hansen again;

Scenario A assumes that the growth rate of trace gas emissions typical of the 1970s and 1980s will continue indefinitely; the assumed annual growth rate averages about 1.5% of current emissions, so the net greenhouse forcing increases exponentially.

If the boys at RC can turn a 1.5%/year increase into an annual decrease I'd like their advice for my next tax return.

 

I note the IPCC page referenced by the RC article cites Hansen 1988, 1998 as a base for it's estimates. A bit like using Hansen 1988 to prove Hansen 1988? Not a big point as there are other papers that agree and are also used by the IPCC. It just strikes me as a bit odd.

[ttowntom]

you've already degenerated into attack mode instead of support your own position mode.

Attack mode? My position has already been amply proven. Warming has not been "underpredicted", it's been consistently overpredicted, nearly always by a huge margin.

 

I entered here with the specific purpose of setting the record straight, which I have.