Don't Cry "Global Warming" Over Spilled Weather!

"It would be stunning, and downright a-physical, if nothing happened to weather as a result of global warming."

This statement reveals the petitio principii fallacy implicit in the current self referential "theory" of catastrophic climate change. You have assumed the conclusion, as part of your premise.

Then to make the situation even more unscientific you attribute any weather related event, well at least negative ones, to climate change. This renders the "theory" unfalsifiable since any outcome reinforces your predetermined conclusion "global warming will cause bad weather events".

Bad weather event A = proof of global warming

Good weather = the heat must be building up, just wait until later!

Bad weather event B = more proof of global warming

It is hard to see how this regimen could produce anything but the conclusion it presupposes. Oh, I guess we could hope for an entire ten years of mild and completely benign weather everywhere on the globe, but that would truly be evidence of something "unprecedented" in the history of the earth.

When it comes to wildfires, or hurricanes, or droughts, or many other weather related phenomena, there is strong published research suggesting that global warming ought to be changing these events in some way in the aggregate, even if we can't detect such changes in any individual occurrence

It seems to me that since you are trying to fix a problem and also come up with future solutions that anything should be fair game to bring up!
Dave Briggs :~)

""It would be stunning, and downright a-physical, if nothing happened to weather as a result of global warming."

This statement reveals the petitio principii fallacy implicit in the current self referential "theory" of catastrophic climate change. You have assumed the conclusion, as part of your premise."

Really? So atmospheric weather is in NO WAY influenced by substances released in large quantities into the atmosphere, which may lead to heat trapping? Weather systems are NOT linked to the earth's thermodynamic system, which converts radiant energy from the sun into many other forms of energy, including wind energy? There is no link between the oceans and tropical cyclonic weather systems that overlay them at certain times of the year? Hum, how did I miss that in all my scientific education?

"There is no link between the oceans and tropical cyclonic weather systems that overlay them at certain times of the year? Hum, how did I miss that in all my scientific education?"

If the threshold is set so low as to be anything above "no link" I guess "anything" is proof of the negative effects of global warming.

Well once you establish...

A) that all or at least most of the 0.6C warming observed over the last century is real and not an artifact of measurement.

B) that warming is demonstrably above what can be shown to be due to natural variabilty.

C) that warming will lead to more and not less, or statistically the same number of storms.

D) that warming will lead to stronger and not weaker or statistically the same strength of storms.

E) that the net effect of those changes will be negative.

Once you cover those minor points you can assert that global warming IS causing more and greater storms that have an over-all adverse effect.

Chris, I don't think that Tierny is saying AGW won't have any effects on the planet, or its weather. What I do think he is saying is that we should stop blaming every oddity the Earth throws at us as a sign of global warming.

You know, this brings back memories of when I lived in the state of New Mexico. The state had been in a particularly nasty 7 year drought which had depleted aquifers and caused some of the biggest forest fires on record. Not unsurprisingly, global warming was the put up as the main factor driving the desertification of a desert state.

Well, the year before I moved away from the state, the drought broke. New Mexico had one of the wettest seasons in many, many years; indeed, it broke a 60 year record for amount of snowfall in one week that December. The city of Albuquerque was paralyzed: forced to use 2 bulldozers to clear the city for 700,000 commuters, schools and government buildings didn't open for another two weeks.

Guess what was blamed for the storm?

If you guessed global warming, you are right.

So which story was right? Did global warming cause snow storms and flash floods, or was it the underlying cause for a devastating drought? It seems pretty hard for it to be both, but that might just be me.

This, I believe, is what Mr. Tierny is talking about. The more you blame on CO2, the less convincing of a case you make.

Chimpy,

"Did global warming cause snow storms and flash floods, or was it the underlying cause for a devastating drought? It seems pretty hard for it to be both..."

That's the beauty of global warming as a political tool, and the reason the term "climate change" is now preferred. You can have your drought and drown it too.

Any extreme weather event, even unusual cold snaps, can be blamed on the more "chaotic" or "non-equilibrium" conditions brought on by the CO2 bogey man. Any minute now an AGW proponent will post something like "Chimpy, heat transfer through underlying ocean currents such as the ENSO can lead to intensified regional anomalies that can lead to either greater cyclone activity or less rain fall depending on the location and timing of these events."

Of course these hand waving exercises prove nothing except that it is easy to produce post hoc explanations that fit preconceived ideas.

As I said it is hard to falsify a theory that predicts everything as a possible result. The fact that even New York Times reporters are catching on to the con game doesn't bode well for the climate hysteria brigade.

Lance,

I've undertaken a long and drawn-out effort to understand global warming as well as a lay-person can, so please bear with me. If you get a chance, please read through my debate with a skeptic at the Richard Dawkins forums.

This statement reveals the petitio principii fallacy implicit in the current self referential "theory" of catastrophic climate change. You have assumed the conclusion, as part of your premise.

The "theory" of anthropogenic global warming, as you put it, is that prodigious greenhouse gas emissions by human activities are warming the planet, that is to say, is introducing an unbalanced radiative forcing into the energy budget of the globe, causing warming. This simple hypothesis has nothing to do with "weather" in the sense of frequency and severity of storms, floods, droughts, cloudiness, precipitation.

The "theory" of global climate change, as you again put it, is that the added warmth will cause an acceleration of the hydrological cycle. If this cycle accelerates, some areas could be flooded by more severe rainfall than they are used to, and some areas could be desertified by even less rainfall than they're used to. Approximately the same amount of water falls, but in less places and more severely. Think of it as putting your thumb over the end of a hose: the same amount of water comes out, but the stream is much more powerful.

This is not at all circular reasoning. This is starting from one hypothesis and proceeding from there, knowing what we know of climate science.

I'll take each of these points in turn:

A) that all or at least most of the 0.6C warming observed over the last century is real and not an artifact of measurement.

I assume you're speaking of urbanization and the heat island effect? Peterson 2003 (PDF) showed that current homogeneity adjustments made on the full datasets account to a statistically insignificant degree for any difference between urban and nearby rural sites. Peterson 1999 showed that in the full datasets, the complete set minus the rural-only set produces a negligible difference. See this (PDF- page 27) for details.

B) that warming is demonstrably above what can be shown to be due to natural variabilty.

Well, you've got me there. There are some periods of natural history where the degree change per decade was 9 degrees Fahrenheit (I can't find direct reference to this, nor remember where I heard it, but since it wounds my argument, I'll accept it as an obstacle). However, all natural variability in the past is fairly well-accounted for. Milankovitch cycles, solar cycles, etc all add up to affect the Earth's temperature. And none of these cycles is currently happening. There has been no correlation between solar activity and global temperature since 1970, when the bulk of warming in the record began. This leads us to ask: Is there a new natural effect at work here we did not previously know about, or is the documented rise in greenhouse gases (and the greenhouse effect is very well-understood) responsible? I'd say in order to claim natural variability, it's up to the claimant to provide evidence to support their position.

C) that warming will lead to more and not less, or statistically the same number of storms.

It's interesting that you should ask this, because it's not really that important. Which would you rather have: More storms of regular intensity with an infrastructure capable of handling regular intensity storms, or less storms of higher intensity with an infrastructure not capable of handling higher intensity?

D) that warming will lead to stronger and not weaker or statistically the same strength of storms.

Warming ocean temperatures will lead to more powerful storms. Warm surface temperatures are well-known to increase the power of a storm that passes over them. While there is no undeniable link between current global warming and the strength of the Atlantic hurricane season, it may be statistically significant that 6 of the top 10 hurricane seasons (in terms of Accumulated Cyclone Energy) occurred within a decade (1995-2005), while the remaining 4 occured within 15 years (1950-1964).

E) that the net effect of those changes will be negative.

When you consider that the last time temperatures were around this high, the human population of the Earth was 1/13th the current size (and many died then, too), it becomes a bit more worrisome that the end is not in sight for current warming trends.

The Pentagon, back in 2003 (PDF), commissioned a report on the national security implications of abrupt climate change (modeled after the 8.2 kYr event). Here's what they had to say:

Recent research, however, suggests that there is a possibility that this gradual global warming could lead to a relatively abrupt slowing of the ocean's thermohaline conveyor, which could lead to harsher winter weather conditions, sharply reduced soil moisture, and more intense winds in certain regions that currently provide a significant fraction of the world's food production. With inadequate preparation, the result could be a significant drop in the human carrying capacity of the Earth's environment.
The research suggests that once temperature rises above some threshold, adverse weather conditions could develop relatively abruptly, with persistent changes in the atmospheric circulation causing drops in some regions of 5-10 degrees Fahrenheit in a single decade. Paleoclimatic evidence suggests that altered climatic patterns could last for as much as a century, as they did when the ocean conveyor collapsed 8,200 years ago, or, at the extreme, could last as long as 1,000 years as they did during the Younger Dryas, which began about 12,700 years ago.

It's worthwhile to note that the Pentagon has no vested interest in global warming alarmism, but is concerned with national security.

Any extreme weather event, even unusual cold snaps, can be blamed on the more "chaotic" or "non-equilibrium" conditions brought on by the CO2 bogey man. Any minute now an AGW proponent will post something like "Chimpy, heat transfer through underlying ocean currents such as the ENSO can lead to intensified regional anomalies that can lead to either greater cyclone activity or less rain fall depending on the location and timing of these events."

Of course these hand waving exercises prove nothing except that it is easy to produce post hoc explanations that fit preconceived ideas.

I wish you could see me raise my eyebrow at the irony of that last paragraph.

Apparently my sarcasm didn't translate through in my last comment. Haven't figured out how to do that yet in this context. Anyway on to threshhold issue - science is not, contrary to popular myth, about certainty. When one works as a scientist, one is taught to develop hypotheses, test them in a rigourous way, report the results, and draw conclusions based on the results, and the best available scientific evidence presented by others. Done correctly, good, sound science generates at least as many questions as it answers.

Lance's five criteria above for scientists to make assertions about the effects of global warming on weather systems are perfectly valid, and probably scientifically testable questions. I suspect we could even find answers to them in the published literature.

What we can't do, however, is determine apriori with 100% accuracy if they are true. That's what our statistician friends would call an impossibility. The only real way to "know" these things are "facts" is to let them occur, measure them, and then analyze them after they are done. That's also part of science as well, but it's not terribly good for management or policy decisions. And, all science aside, that's what global warming is - a policy issue.

So Lance, we'll never get any certainty until after it's over. That's the only given. My question still is do we want to wait until we absolutely, 100%, beyond any statistical or reasonable doubt certain about global warming to address, as a matter of policy, a scientifically based issue that the vast majority of science has, indeed, come to a consensus on? I don't - doesn't bode well for the world I'll leave my children or their children.

Philip L. Hoffman

Chimpy-

So which story was right? Did global warming cause snow storms and flash floods, or was it the underlying cause for a devastating drought? It seems pretty hard for it to be both, but that might just be me.

It could actually be both, as accelerating the hydrological (precipitation) cycle can have the paradoxical effect of reducing rainfall frequency and producing powerful rainfall at the same time.

This site (albeit for kids) is a good description of the effects of accelerating the hydrological cycle.
http://www.epa.gov/climatechange/kids/water_cycle_version2.html

For the record, I happen to agree that individual weather anomalies cannot (or at least should not) be attributed to global warming, but trends in weather patterns can be reasonably correlated. Trends such as the recent European heatwaves and arctic ice minima.

@AA-

I understand how global warming can cause both dry times and extra rain. My problem with the New Mexico case is not that people said that AGW was causing extra rain and less rain at the same time, but that they said the two were occurring in the exact same place at the same time. Even the EPA link you gave me does not attempt to say that one area will become both wetter and dryer- they showed that there was a clear distinction between the "Dry Cycle" and the "Wet Cycle," did they not?

This brings us back to my original point. Clearly AGW was not the root of every weather event that happened in Albuquerque. I must conclude that the scientists and journalists covering the issue were dishonest- or overzealous- in their discussion of the local effects of climate change in the state. A better discussion might be: how do we stop the genuine alarmists from exaggerating to the point of their message's destruction?

P.S. I should also probably say that one of the reasons I enjoy reading this blog so much is that Chris & Sheryl don't fall into the "Every problem you can ever imagine happening is the direct result of GLOBAL WARMING " trap. Keep up the good work!

AtheistAcolyte,

I appreciated the thoughtful tone of your reply, except perhaps for the bit at the end that insinuated that I might be selectively interpreting evidence to suit my preconceptions. As a scientist I bring nothing to this topic other than my natural skepticism and my training as a physicist.

Not that it matters to the issue at hand, but I am also an atheist and thought I'd give a "shout out" to a fellow free thinker.

The "debate" you link to seems to be a typical "warmer"/"denier" blog food fight.
I'm not in the mood to toss Jello at the moment, but I will make a few points in reference to your response.

First, Peterson 2003 is a flawed attempt to remove the UHI thorn from the surface temperature record. This is a good place to start for a critical examination of the problems with that study.

Second, you attempt to turn the question around by saying "I'd say in order to claim natural variability it's up to the claimant to provide evidence to support their position."

I beg your pardon? Perhaps your lack of scientific training is showing here. AGW is making the claim that the observed warming is NOT due to the only other possibility, natural variability. As an atheist, you of all people, should understand that it is incumbent upon the person MAKING the extraordinary claim to provided conclusive evidence and that the converse is irrational! This is akin to a believer saying "Prove that natural forces brought about the creation of the universe" in response to an atheist requesting positive evidence for divine creation.

Third and fourth, your statement "Warming ocean temperatures will lead to more powerful storms" is far from a scientific fact. A direct link between higher SST's and tropical storm intensity is a matter of some contention in the literature at the moment. If you do a cursory search you will find papers on both sides of this issue. You seem to be playing a little loose with the evidence.

Fifth, your Pentagon study reply is perhaps the most disreputable of your points. If you have actually read the study you know that this study was prepared as a "worst case scenario" that PRESUPPOSED many clearly improbable and unscientific events, such as the shutdown of the thermohaline current, and then tried to predict a military response to deal with them. These types of scenarios are prepared by the military in response to a wide variety of unlikely "just in case" events. It hardly represents a study that supports the probability of these calamities occurring.

It is my hope that the same skepticism that you applied to reject the proposition that a deity controls the universe will lead you to further investigate the tenuous evidence supporting AGW catastrophism. I will skip the insulting parting shot impuning your motives.

Yours in reason,

Lance

Damn, misspelled impugning! I must learn to use a spell checker.

I appreciated the thoughtful tone of your reply, except perhaps for the bit at the end that insinuated that I might be selectively interpreting evidence to suit my preconceptions. As a scientist I bring nothing to this topic other than my natural skepticism and my training as a physicist.

The reason I felt it ironic was because your statement sounded very 'hand-wavy' to me. As in, you were dismissing out-of-hand all explanations for why a complex and chaotic system might not behave the way you would expect it to. The argument you made as an example, true or not, was very detailed and as such subject to critical analysis, and at the very least a probability assessment. CAN (that is to say, is it at all possible) an ocean current such as ENSO carry heat to produce intensified yadda yadda yadda? Establishing that, how likely is it that it should happen in this case?

Answering a question like that is beyond my knowledge at the moment, but dismissing it as an example of "post hoc explanations that fit preconceived ideas" is not reasonable.

Not that it matters to the issue at hand, but I am also an atheist and thought I'd give a "shout out" to a fellow free thinker.

Ditto.

I have seen McIntyre's rebuttal of Peterson 2003 and find it lacking in substance. It seems he considers historical trends on a subset of the full data a worthwhile response to a cluster analysis of homogeneity adjustment efficacy. P2003 doesn't make the claim that there is not a trend in the raw historical data for their 40 sites, but instead makes the claim that the difference between adjusted urban site data and their correlating adjusted rural data is statistically insignificant.

That is to say, current adjustment schema reasonably homogenize the data to account for any urbanization effects.

Peterson 1999, on the other hand (and I can't find any links to the full text of this report, but my other linked PDF shows a similar situation on page 27), takes the full adjusted urban+rural dataset and subtracts the full adjusted rural-only dataset and finds no reasonable difference. In the words of P2003:

To find out how contaminated global temperature trends were from the UHI, Peterson et al. (1999) identified each station in GHCN using both the map-based and the satellite-based metadata. Two time series were then created. One was the time series from the full dataset, the one used routinely to determine global temperature trends over land areas at the National Climatic Data Center (e.g., Lawrimore et al. 2001), and another one produced using only data from stations that were identified as rural by both techniques. The two time series were very similar. The linear trend from 1880 to 1998 was 0.65 [degrees] C [per] century for the full dataset and the slightly higher 0.70 [degrees] C [per] century for the rural-only subset. The resulting conclusion was that the well-known global temperature time series from in situ stations was not significantly impacted by urban warming.

I beg your pardon? Perhaps your lack of scientific training is showing here. AGW is making the claim that the observed warming is NOT due to the only other possibility, natural variability. As an atheist, you of all people, should understand that it is incumbent upon the person MAKING the extraordinary claim to provided conclusive evidence and that the converse is irrational! This is akin to a believer saying "Prove that natural forces brought about the creation of the universe" in response to an atheist requesting positive evidence for divine creation.

I say the onus is on you, because I feel the reasonable case has been made with the following argument:

Human activities result in carbon emissions.
These anthropogenic carbon emissions are significantly altering the carbon dioxide component of the atmosphere. (Current carbon dioxide levels are more than 40% above pre-industrial levels, and the ratio of carbon-12 to carbon-13 has dropped due to fossil fuel usage).
The carbon dioxide component is well-known to be involved in the greenhouse effect which warms this planet.
Current (and common-sense) understanding of the greenhouse effect tells us that as greenhouse gas concentrations rise, so too does the absorption of energy from the sun, creating a warming effect.
Instrumental records show a warming effect divergent from any known natural variability (solar forcing has been divergent from the current warming since approximately 1970).

Ergo, carbon-emitting human activities cause global warming.

This is a reasonable and logical argument, supported by research and instrumental records. If you expect me to believe that natural variability can account for the current array of evidence, you must present an argument which not only explains the evidence at hand coherently, but also explains why my argument is mistaken. Also, it would be preferable if it contained a falsifiable prediction contrary to my argument.

Third and fourth, your statement "Warming ocean temperatures will lead to more powerful storms" is far from a scientific fact. A direct link between higher SST's and tropical storm intensity is a matter of some contention in the literature at the moment. If you do a cursory search you will find papers on both sides of this issue. You seem to be playing a little loose with the evidence.

Perhaps in some regard, I can be seen as "playing loose" with the facts, but it's simply a matter of temperature. According to Knutson 2004 (PDF), warming due to CO2 will introduce a bias towards the more intense storms. Not an increase in general storm frequency, mind you, but an increase in intensity, precipitation, wind strength, you name it. Of course you can't attribute an individual storm or season to global warming, as RealClimate is the first to point out. But we can make statistical assessments and statistical predictions. To take their example:

The situation is analogous to rolling loaded dice: one could, if one was so inclined, construct a set of dice where sixes occur twice as often as normal. But if you were to roll a six using these dice, you could not blame it specifically on the fact that the dice had been loaded. Half of the sixes would have occurred anyway, even with normal dice. Loading the dice simply doubled the odds. In the same manner, while we cannot draw firm conclusions about one single hurricane, we can draw some conclusions about hurricanes more generally. In particular, the available scientific evidence indicates that it is likely that global warming will make - and possibly already is making - those hurricanes that form more destructive than they otherwise would have been.

Finally, about the Pentagon study, I'll leave it to their own words:

We have created a climate change scenario that although not the most likely, is plausible...

There are some indications today that global warming has reached the threshold where the thermohaline circulation could start to be significantly impacted. These indications include observations documenting that the North Atlantic is increasingly being freshened by melting glaciers, increased precipitation, and fresh water runoff making it substantially less salty over the past 40 years.

This report suggests that, because of the potentially dire consequences, the risk of abrupt climate change, although uncertain and quite possibly small, should be elevated beyond a scientific debate to a U.S. national security concern.

While this is not a slam-dunk endorsement of my position, it does help establish that warming can have a net negative impact on human civilization, which was my reason for bringing it up in the first place.

Atheist Acolyte,

Peterson's conclusions are based on comparisons of urban temperature records with rural temperature records. His choice of what represents urban and rural is one of the main problems with the analysis. You claim that McIntyre's criticisms "lack substance". I found his in depth analysis, critical of Peterson's study, quite compelling.

You seem to be missing McIntyre's point that Peterson fails to segregate actual "urban" sites from "rural" ones and hence it is hardly surprising that such a false comparison yields the statistically insignificant results reported by Peterson. Also only about 25% of the sites chosen by Peterson even occur in the USHCN network or GHCN network thus it is dubious to use this data to make claims on whether urbanization affects the CRU, NOAA or GISS composites.

I say the onus is on you, because I feel the reasonable case has been made with the following argument.

Well, let's look at that argument.

Human activities result in carbon emissions.

OK, so far so good.

These anthropogenic carbon emissions are significantly altering the carbon dioxide component of the atmosphere. (Current carbon dioxide levels are more than 40% above pre-industrial levels, and the ratio of carbon-12 to carbon-13 has dropped due to fossil fuel usage).

Not to quibble but the "pre-industrial CO2 level" is generally thought to be 280ppm and the current level is 384ppm (RealClimate). So your "more than 40% above" statement is false (280ppm x 1.4 = 392ppm) if only by 9ppm.

The carbon dioxide component is well-known to be involved in the greenhouse effect which warms this planet.

The "enhanced" greenhouse effect actually, but OK.

Current (and common-sense) understanding of the greenhouse effect tells us that as greenhouse gas concentrations rise, so too does the absorption of energy from the sun, creating a warming effect.

Yes, but since it's a logarithmic relationship additional CO2 will lead to smaller increases in temperature.

Instrumental records show a warming effect divergent from any known natural variability (solar forcing has been divergent from the current warming since approximately 1970).

Not so fast there AA. There is plenty of evidence that past climate temperatures varied by greater amounts and at similar or greater rates of change than what has been claimed over the last one hundred years.

Ergo, carbon-emitting human activities cause global warming.

I can't even say I disagree with this conclusion actually; in as far as it goes. I notice it makes no claim to any warming that would be above the level of noise against the back ground of natural variability or that it is "dangerous" in any way.

Hence, even overlooking your flawed premises you are saying very little here, certainly nothing warranting an overhaul of the entire world's energy economy.

Peterson's conclusions are based on comparisons of urban temperature records with rural temperature records. His choice of what represents urban and rural is one of the main problems with the analysis. You claim that McIntyre's criticisms "lack substance". I found his in depth analysis, critical of Peterson's study, quite compelling.

You seem to be missing McIntyre's point that Peterson fails to segregate actual "urban" sites from "rural" ones and hence it is hardly surprising that such a false comparison yields the statistically insignificant results reported by Peterson. Also only about 25% of the sites chosen by Peterson even occur in the USHCN network or GHCN network thus it is dubious to use this data to make claims on whether urbanization affects the CRU, NOAA or GISS composites.

Two points:
1) Peterson 2003 used satellite night-light data to determine urban/suburban/rural sites (using the Owens et al. 1998 methodology). This is the same adjustment used in the full datasets. I'm not sure why you think it's so far off-course?

2) You are still missing the point that Peterson 2003 was about establishing the efficacy of adjustments in homogenizing data by looking at clusters of data across a geographically diverse space. It doesn't matter if the data is not entirely used in the full datasets; As long as they are in situ temperatures with acceptable metadata attached, there isn't a problem. This is about verifying the process.

Not to quibble but the "pre-industrial CO2 level" is generally thought to be 280ppm and the current level is 384ppm (RealClimate). So your "more than 40% above" statement is false (280ppm x 1.4 = 392ppm) if only by 9ppm.

Apologies. I was going off memory and for some reason 270 has stuck in my mind. I hereby amend my statement to "more than 30% above". Does that satisfy you?

The "enhanced" greenhouse effect actually, but OK.

If you'll quibble, I'll quibble. Carbon dioxide has an important component to play in the Greenhouse Effect. I'm getting to the "enhanced" bit.

Yes, but since it's a logarithmic relationship additional CO2 will lead to smaller increases in temperature.

I'm glad you mentioned that, because it gives me an opportunity to show my own graph of this logarithmic relationship, together with certain milestones in expected growth. The atmospheric concentration is normalized to pre-industrial levels (I can't remember the concentration I used, but it could have been 270. Whatever my starting point, the formula still follows-- our dots just move slightly). You will notice it took us 150 years to move a fairly small (graphically) amount. However, projections say we will reach 2x pre-industrial CO2 in 50 years, and will move a slightly larger graphical distance. While CO2 emissions may have a diminishing impact on the atmosphere, our emissions are accelerating. The formula is taken from the IPCC TAR (Table 6.2, page 358, I believe).

Further, other greenhouse gases (such as methane, contained in permafrost and peat bogs) are not limited by this logarithmic relationship; methane is linear. And as temperatures rise, these methane sinks will begin to release their contents.

Not so fast there AA. There is plenty of evidence that past climate temperatures varied by greater amounts and at similar or greater rates of change than what has been claimed over the last one hundred years.

Never said there wasn't. What I meant was that there is no currently understood natural forcing agent at work here. There has been no correlative change in the incident solar output in 30 years. Milankovitch cycles aren't at play. What other natural effect can be at work? (Which is right back where we started-- The onus is on you to provide a description of a natural forcing agent which agrees with the current data)

I can't even say I disagree with this conclusion actually; in as far as it goes. I notice it makes no claim to any warming that would be above the level of noise against the back ground of natural variability or that it is "dangerous" in any way.

Hence, even overlooking your flawed premises you are saying very little here, certainly nothing warranting an overhaul of the entire world's energy economy.

I wasn't making an argument for an overhaul of the energy economy or that it was dangerous. Rather, I was presenting the argument that certain human activities are causing global warming, and showing how a rational argument is made for anthropogenic sources of the current warming trend, and that any natural variability must provide its' own evidence (solar output correlation, orbital mechanics discussion, or little green men from Mars).

AA,

What do you suppose "caused" the end of the little ice age if one need "explain" temperature variations of less than one degree? None of the forces you claim as the only alternatives to man made CO2 ("solar output correlation, orbital mechanics discussion, or little green men from Mars") were responsible for the variation in global temps that have been melting glaciers since the middle of the last millennium.

The little ice age is a long accepted fact. There is certainly plenty of historical and scientific proxy data to support the conclusion that the warming of the last one hundred years falls well within the observed range of natural variability or are you one of the prevaricators attempting to rewrite climate history?

Lance,

Have you read The Little Ice Age: How Climate Made History, 1300-1850 by Brian Fagan? (The subtitle has been changed for the paperback to The Prelude to Global Warming, 1300-1850.) Click my name to read my review.

I usually cite the book to point out how small natural variations caused major societal problems, which suggests that the larger temperature increases (even the lower limits) predicted by the IPCC for the coming century are potentially even more ominous for geopolitics (as well as the geography itself of low-lying areas on island nations and every continent).

But the book makes the case quite strongly that the natural variations of the Little Ice Age ended when human contributions to the climate took over.

You seem to be stuck on ten-year-old arguments about natural variation that have been rejected by the overwhelming majority of climate scientists.

What do you suppose "caused" the end of the little ice age if one need "explain" temperature variations of less than one degree?

It's not so much that I need to "explain" this change, it's that for the recent past (let's say the past 5,000 years), this change is rather unprecedented, including the MWP and LIA (for which the consensus is not in yet AFAIK on regional/global status). Current understanding (again, AFAIK) is that the end of the LIA was not so much "caused" as the LIA's cause ended: Solar activity was thought to be at a minimum during that period, based on proxies such as sunspots and C-14 and Be-10, and began coming out of its' minima around the time the LIA ended. Likewise, it was thought to be at a maximum around the MWP (with a dip, at it's lowest still significantly above the LIA average, from 1000-1150).

At any rate, it doesn't matter what happened during the LIA or MWP, because this rate of change is happening now, and the case is reasonably made that it is due to anthropogenic greenhouse gas emissions, therefore any claim of natural variability must be attributed to some source, not simply handwaved away.

The little ice age is a long accepted fact. There is certainly plenty of historical and scientific proxy data to support the conclusion that the warming of the last one hundred years falls well within the observed range of natural variability or are you one of the prevaricators attempting to rewrite climate history?

I'm rather confused by what you mean by natural variability. Do you mean absolute temperature or magnitude of trends? What's the time scale for this "natural variability"? Are you talking natural variability in terms of the Phanerozoic eon, or the Holocene epoch? Are you saying that within a distribution curve of temperature changes, the current change is within a significant percentile? I'd like to see the research done on that.

As a trained scientist, you must appreciate the necessity of defining terminology. How do you mean to use "natural variability" in this statistical sense?