Why the Historical Warming Numbers Matter

First, let's settle something.  The world has warmed since 1850.  While there always is an error bar on nearly every statement about nature, I think there is little point in questioning this past warming.  There is ice core data that suggests that the little ice age, which ended some time in the very early 19th century, was perhaps the coldest period, or one of the two or three coldest periods, in the last 5000 years (ie in nearly the entire span of human civilization).  Temperatures are inevitably warming from this low point.(*1)

So, if the point is not to deny warming altogether, what is the point in discussions of Climategate of picking over and trying to audit historical temperature records like the Hadley CRUT3 or NASA's GISStemp?  Skeptics often argue that much of the warming is due to bogus manual adjustments in the temperature records and biases such as urban warming.  Alarmists argue that the metrics may understate warming because of masking by manmade anthropogenic cooling agents (e.g. sulfate aerosols).  Why bother?  Why does it matter if past warming is 0.6C or 0.8C or 0.3C?  There are at least two reasons.

1.  The slope of recent temperature increases is used as evidence for the anthropogenic theory.

We know greenhouse gasses like CO2 have a warming effect in the lab.  And we know that overall they warm planets because otherwise ours would be colder.  But how much does an incremental amount of CO2 (a relatively weak greenhouse gas) warm the Earth?  A lot or a little?  Is the sensitivity of the climate to CO2 high or low?

Every time I try to express this, it sounds so ridiculous that people think I must have it wrong.  But the main argument supporting a high climate sensitivity to CO2 is that scientists claim to have looked at past warming, particularly from 1950-2000, and they can't think of any natural cause that could behind it, which leaves CO2 by process of elimination.  Yeah, I know this seems crazy - one wants to ask if this is really a test for CO2 sensitivity or of scientists' understanding and imagination, but there you have it.

Now, they don't always say it this directly.  What they actually say is that they ran their climate models and their climate models could not produce the warming from 1950-2000 with natural forcings alone, but could reproduce this warming with forcings from CO2.  But since the climate models are not handed down from the gods, but programmed by the scientists themselves to represent their own understanding of the climate system, in effect this is just a different way of saying what I said in the previous paragraph.   The climate models perform the function of scientific money laundering, taking an imperfect knowledge on the front end and somehow converting that into settled science at the output.

Now, there are a lot of ways to criticize this approach.  The models tend to leave out multi-decadal ocean cycles and don't really understand cloud formation well.  Further, the period from 1957-2008, which supposedly can only be explained by non-natural forcings, has almost the exact same temperature profile and increase as the time from 1895-1946, which of necessity must be mostly "natural."  I go into this more here, among other places.

But you can see that the amount of warming matters to this argument.  The more the warming falls into a documented natural range of temperature variation, the harder it is to portray it as requiring man-made forcings to explain.  This is also the exact same reason alarmist scientists work so hard to eliminate the Medieval Warm Period and little ice age from the temperature record.  Again, the goal is to show that natural variation is in a very narrow range, and deviations from this narrow range must therefore be man-made. (*2)

This is the sort of unified field theory of everything we are seeing in the CRU emails.   We see scientists using every trick they can find to lower or smooth out temperatures numbers before 1950, and adjust numbers after 1950 upwards.  Every single trick and programming adjustment all tended to have this effect, whether it be in proxy studies or in the instrumental record.  And all the efforts to prevent scrutiny, ignore FOIA's, and throw out raw data have been to avoid third party replication of the statistical methods and adjustments they used to achieve these ends.

As an aside, I think it is incorrect to picture this as a SPECTRE-like cabal scheming to do evil.   These guys really, really believed they had the right answer, and these adjustments were made to tease out what they just knew the right answer to be.  This is why we are only going to see confused looks from any of these guys - they really, really believed they were doing God's work.  They are never going to understand what they did wrong.  Which doesn't make it any less bad science, but just emphasizes that we are never going to get data without spin until total sunlight is brought to this process

2.  It is already really hard to justify the huge sensitivities in alarmist forecasts based on past warming -- if past warming is lower, forecasts look even more absurd.

The best way to illustrate this is with a few charts from my most recent climate presentation and video.  We usually see warming forecasts by year.  But the real relationship is between warming and CO2 concentration (this relationship is called climate sensitivity).   One can graph forecasts at various levels:


The blue line corresponds to the IPCC no-feedback formula that I think originally goes back to Michael Mann, and yields about 1-1.2C of warming for greenhouse gas warming from CO2 before feedback effects.  The middle two lines correspond to the IPCC mid and high forecasts, and the top line corresponds to more alarmist forecasts from folks like Joe Romm who predict as much as 8-10C of warming by 2100 (when we will be at 650-800ppm CO2 per the IPCC).  By the way, the IPCC does not publish the lines above the blue line, so I have taken the formula they give for the blue line and scaled it to meet their end points.  I think this is reasonable.

A couple of things - all climate models assume net positive feedback, what skeptics consider the key flaw in catastrophic global warming theory.  In fact, most of the catastrophe comes not from global warming theory, but by this second theory that the Earth's temperature system is dominated by very high positive feedback.  I illustrate this here.  The blue line is from CO2 greenhouse gas warming.  Everything above it is from the multiplier effects of assumed feedbacks.


I won't go into the feedback issue much now - search my site for positive feedback or else watch my video for much more.  Suffice it to say that skeptics consider the feedback issue the key failure point in catastrophic forecasts.

Anyway, beyond arguing about feedbacks, there is another way to test these forecasts.   Relationships that hold for CO2 and warming in the future must hold in the past (same Earth).  So lets just project these lines backwards to the CO2 level in the late 19th century.


Can you see the issue?  When projected back to pre-industrial CO2 levels, these future forecasts imply that we should have seen 2,3,4 or more degrees of warming over the last century, and even the flawed surface temperature records we are discussing with a number of upwards biases and questionable adjustments only shows about 0.6C.

Sure, there are some time delay issues, probably 10-15 years, as well as some potential anthropogenic cooling from aerosols, but none of this closes these tremendous gaps.  Even with an exaggerated temperature history, only the no feedback 1C per century case is really validated by history.  And, if one assumes the actual warming is less than 0.6C, and only a part of that is from anthropogenic CO2, then the actual warming forecast justified is one of negative feedback, showing less than 1C per century warming from manmade CO2 -- which is EXACTLY the case that most skeptics make.

Those who control the past control the future. Those who control the present control the past.- George Orwell


(1) More than once I have contemplated how much the fact that the invention of the thermometer occurred at perhaps the coldest point in human memory (early 17th century)  has contributed to the perceptions of current warm weather being unusual.

(2) For those who are on the ball, perhaps you can spot an amazing disconnect here.  Scientists claim that the natural variation of temperatures is in a very narrow band, that they never move even 0.2C per decade by natural means.  But they also say that the Earth's temperature system is dominated by positive feedback, meaning that very very small changes in forcings are magnified many fold in to large temperature changes.  I won't go in to it in depth from a systems perspective, but trust me that "high stability in a narrow range" and "dominated by high positive feedback" are not very compatible descriptions of a system.


  1. tomw:

    Your last sentence:
    "I won’t go in to it in depth from a systems perspective, but trust me that “high stability in a narrow range” and “dominated by high positive feedback” are not very compatible descriptions of a system."

    The description is like saying that "you can steer a car in a narrow track easily.." when it has a "very sensitive steering mechanism".
    Yeah, sure. Move the steering wheel a tiny bit -high positive feedback - and the car responds by yawing into the next lane, not by staying 'stable in a narrow range.'
    Wonder what they've been smoking...

  2. Brad K.:

    I watched a video this week, where the speaker classified "fundamentalist" Christions as refusing to listen. That seems to apply to victim disarmers and global warmers, too. I would have called that fanaticism, myself. Or intolerant.

    It is *important* to preach to the choir, to repeat and explain and illustrate what we know. Doing so keeps us all honest and engaged. Thanks!

  3. Link:

    Is the following right?

    AGW Conclusion 1: Because the recent data shows a lot of warming and these scientists can't otherwise account for this phenomenon, they concluded that man-made CO2 had to be the cause.

    AGW Conclusion 2: If CO2 can cause that much change that quickly then it has magical thermodynamic properties. Thus these changes will continue until we hit catastrophe.

    As to #1, wouldn't most scientists first go back and rethink their data collection practices. If you look at timeline from 1998 on, it looks like these guys didn't want to admit they made a mistake. It also looks like they had a great ability to cherry pick data sets, etc, etc so they could always pull a rabbit out of the hat. There are many potential flaws in the way they were collecting data, even if they were honest about it. Personally, to me it feels like at least a few of these guys are rats. Michael Mann for one is a serial data molester.

    Further -- even if the data were right -- to infer that CO2 is the cause doesn't logically follow. CO2 might be the cause, but it might not. Think of it like a criminal investigation. The data tells you "there's a dead body on the floor." At that point CO2 is a suspect -- but just because it's the only suspect you've identified doesn't mean CO2 is necessarily guilty. It's like convicting someone because he was the only one seen going into the room with the dead body.

    Which leads into #2,

    CO2 is a trace gas -- that means there's very little of it. I've estimated that the mass of all the CO2 in the air is less than the mass of the top inch of our oceans. To say it drives the temperature of the planet would require it to have magical thermodynamic properties. Just calling it a greenhouse gas doesn't address this. It has to do with scale. An ounce of a poison can kill you if put into a glass of water -- but have no affect if put into a reservoir. If CO2 had these magical properties, we should be making heat pumps with it.

    Further, we've had much higher levels of CO2 in the air in the past, and Earth went through its Ice Age cycles just fine. Which is evidence that CO2 doesn't in fact have magical thermodynamic properties.


    Another big issue is that AGW is focused on the last 1,000 years and especially the last century. But we have millions of years of climate change history that AGW science seems to ignore. A stastician would say that any short-term blips are just normal noise in the bigger scheme of things.

    I also don't know how you can have a climate science that can make conclusions about AGW without high confidence that you first understand totally the effects of the Sun because it's potentially such an overwhelming factor.

    Physicists at CERN have been dabbling in climate change. One theory they're working on is that the controlling mechanism of climate change is cloud formation driven by cosmic rays which are modulated by variations of the solar wind, which in turn is controlled by sunspot activity. The following link includes a video of a June 2009 70 minute presentation: http://seekingalpha.com/article/175641-climategate-revolt-of-the-physicists

    An important point is that flawed AGW data has probably affected the pursuit of alternative theories like sunspot activity.

  4. EscapedWestOfTheBigMuddy:

    The climate models perform the function of scientific money laundering, taking an imperfect knowledge on the front end and somehow converting that into settled science at the output.

    You can certainly do this with a model, but it is not supposed to be the point.

    You are supposed to use a model when you have a good handle on all the micro-physical behaviors, but can't run experiments on the full sized system. Doing that gives you a chance of leaning something that didn't put stick into the model in the first place (of course, you have to follow up to prove it).

    Saying the model can't match the data so ::favorite unmodeled effect:: must be at work in the system is non actually inane, but it does require that you have categorically refuted the presence or importance or other unmodeled effects.

  5. jj:

    Where did you get the feedback curves from? It looks like you assumed an exponent less than 1 -- this produces decelerating warming, which is an equal and opposite assumption to the accelerating warming used to justify the more extreme warming predictions.

    I'd hate to see you use their wobbly assumptions.

  6. JAdkins:

    Tomw - First - anyone can describe a positive feedback system. But that does not mean earth's climate system is subject to a positive feedback. Name a few in nature. Secondly, there have been enough volcanic eruptions to conclude that the earth's climate system is subject to negative feedback.

    Secondly, put that same car and lane in a tunnel, and you have negative feedback.

  7. Larry Zane:

    The scientific consensus that once backed the man-made global warming theory is quickly becoming a crap pile. The new theory based upon cosmic rays and solar activity, is proving to be much more predictive of climate change, with carbon dioxide playing a minor role if any. .

  8. Dr. T:

    "These guys really, really believed they had the right answer, and these adjustments were made to tease out what they just knew the right answer to be."

    Why would you make this assumption? I don't assume they are mediocre scientists who are rationalizing their 'honest' mistakes. I assume that they jumped on the anthropogenic global warming bandwagon because that is how climatologists get funding from governments and environmental groups. And if it took data modification and bizarre climate model manipulation to get there, well, these money-grubbing pseudoscientists didn't care. These climatologist jackasses are worse than the physicists who claimed they created cold fusion, and they deserve no respect for their 'scientific' work.

  9. O Bloody Hell:

    > We know greenhouse gasses like CO2 have a warming effect in the lab. And we know that overall they warm planets because otherwise ours would be colder.

    A specious basis for any argument in either direction on Goebbels' Warming Theory... It's accurate in so far as the notion that planets with atmospheres tend to be warmer than planets without, but that's like saying we should beware of neon in the atmosphere, because it could cause Goebbels' Warming, too.

    The notion that CO2 acts as a so-called "GHG" ignores all sorts of subtle relevancies, and works to oversimplify (and, thus, inaccurately suggest understanding of) one of the three or four most complex systems humans have actually attempted to model in the last 50-odd years (economics being one of the others).

    Perhaps you might've noticed how well that economics modeling was working of late? The true fact in both cases is that we've got a long, long way to go before we have any clue of any kind as to how to make reliable forecasts of any sort in either field.

    The Swartzberg Test:
    The validity of a science is its ability to predict.

    Goebbels' Warming == negative validity....