The Critical Flaw with Catastrophic Global Warming Theory

I began with an 85-page book.  I shortened that to a 50-minute film, and then a 9-minute film.  With that experience, I think I can now pull out and summarize in just a few paragraphs why we should not fear catastrophic global warming.  Here goes:

Climate catastrophists often argue that global warming theory is "settled science."  And they are right in one respect:  We have a pretty good understanding of how CO2 can act as a greenhouse gas and cause the earth to warm.  What is well agreed upon, but is not well communicated in the media, is that a doubling of CO2, without other effects that we will discuss in a moment, will heat the earth about 1 degree Celsius (plus or minus a few tenths).  This is not some skeptic's hallucination -- this is straight out of the IPCC third and fourth assessments.  CO2, acting alone, warms the Earth only slowly, and at this rate we would see less than a degree of warming over the next century, more of a nuisance than a catastrophe.

But some scientists do come up with catastrophic warming forecasts.  They do so by assuming that our Earth's climate is dominated by positive feedbacks that multiply the initial warming from CO2 by a factor of three, four, five or more.  This is a key point -- the catastrophe does not come from the science of greenhouse gases, but from separate hypotheses that the earth's climate is dominated by positive feedback.  This is why saying that greenhouse gas theory is "settled" is irrelevant to the
argument about catastrophic forecasts.  Because these positive feedbacks are NOT settled science.  In fact, the IPCC admits it does not even know the sign of the most important effect (water vapor), much less its magnitude.  They assume that the net effect is positive, but they are on very shaky ground doing so, particularly since having long-term stable systems like climate dominated by positive feedback is a highly improbable.

And, in fact, with the 100 or so years of measurements we have for temperature and CO2, empirical evidence does not support these high positive feedbacks.  Even if we assign all the 20th century warming to CO2, which is unlikely, our current warming rates imply close to zero feedback.  If there are other causes for measured 20th century warming other than CO2, thereby reducing the warming we blame on CO2, then the last century's experience implies negative rather than positive feedback in the system.  As a result, it should not be surprising that high feedback-driven forecasts from the 1990 IPCC reports have proven to be way too high vs. actual experience (something the IPCC has since admitted).

However, climate scientists are unwilling to back down from the thin branch they have crawled out on.  Rather than reduce their feedback assumptions to non-catastrophic levels, they currently hypothesize a second man-made cooling effect that is masking all this feedback-driven warming.  They claim now that man-made sulfate aerosols and black carbon are cooling the earth, and when some day these pollutants are reduced, we will see huge catch-up warming.  If anything, this cooling effect is even less understood than feedback.  What we do know is that, unlike CO2, the effects of these aerosols are short-lived and therefore localized, making it unlikely they are providing sufficient masking to make catastrophic forecasts viable.  I go into several reality checks in my videos, but here is a quick one:  Nearly all the man-made cooling aerosols are in the northern hemisphere, meaning that most all the cooling effect should be there -- but the northern hemisphere has actually exhibited most of the world's warming over the past 30 years, while the south has hardly warmed at all.

In sum, to believe catastrophic warming forecasts, one has to believe both of the following:

  1. The climate is dominated by strong positive feedback, despite our experience with other stable systems that says this is unlikely and despite our measurements over the last 100 years that have seen no such feedback levels.
  2. Substantial warming, of 1C or more, is being masked by aerosols, despite the fact that aerosols really only have strong presence over 5-10% of the globe and despite the fact that the cooler part of the world has been the one without the aerosols.

Here's what this means:  Man will cause, at most, about a degree of warming over the next century.  Most of this warming will be concentrated in raising minimum temperatures at night rather than maximum daytime temperatures  (this is why, despite some measured average warming, the US has not seen an increase of late in maximum temperature records set).  There are many reasons to believe that man's actual effect will be less than 1 degree, and that whatever effect we do have will be lost in the natural cyclical variations the climate experiences, but we are only just now starting to understand.

To keep this relatively short, I have left out all the numbers and such.  To see the graphs and numbers and sources, check out my new climate video, or my longer original video, or download my book for free.

UPDATE: Based on a lot of comment activity to this post at its mirror at Climate Skeptic,
I wanted to add a bit of an update.  It is sometimes hard to summarize
without losing important detail, and I think I had that happen here.

Commenters are correct that positive feedback dominated systems can
be stable as long as the feedback percentage is less than 100%.  By
trying to get too compact in my arguments, I combined a couple of
things.  First, there are many catastrophists that argue that climate
IS in fact dominated by feedback over 100% -- anyone who talks of
"tipping points" is effectively saying this.  The argument about
instability making stable processes impossible certainly applies to
these folks' logic.  Further, even positive feedback <100% makes a
system highly subject to dramatic variations.  But Mann et. al. are
already on the record saying that without man, global temperatures are
unbelievably stable and move in extremely narrow ranges.   It is hard
to imagine this to be true in a climate system dominated by positive
feedback, particularly when it is beset all the time with dramatic
perturbations, from volcanoes to the Maunder Minimum.

To some extent, climate catastrophists are in a bind.  If historic
temperatures show a lot of variance, then a strong argument can be made
that a large portion of 20th century warming is natural occilation.  If
historic temperatures move only in narrow ranges, they have a very
difficult time justifying that the climate is dominated by positive
feedbacks of 60-80%.

The point to remember, though, is that irregardless of likelihood,
the historical temperature record simply does not support assumptions
of feedback much larger than zero.  Yes, time delays and lags make a
small difference, but all one has to do is compare current temperatures
to CO2 levels 12-15 years ago to account for this lag and one still
gets absolutely no empirical support for large positive feedbacks.

Remember this when someone says that greenhouse gas theory is
"Settled."  It may or may not be, but the catastrophe does not come
directly from greenhouse gasses.  Alone, they cause at most nuisance
warming.  The catastrophe comes from substantial positive feedback (it
takes 60-80% levels to get climate sensitivities of 3-5C) which is far
from settled science.


  1. Jim Hart:

    I'm really glad you are on the planet. Could be a sappy thing to say, but my life is better for reading your works.

  2. Bearster:

    Warren: not to mention the gross flaws in how temperature is measured. Urban warming around the temperature probes could account for 100% of the measured warming. Or it could be that urban warming is actually masking a small amount of cooling. We can't say because we have a small set of temperature probes (considering the size of the system we're trying to measure). And the data from many of these probes is suspect due to urban waming.

    Whatever it is that you'd call it when people make big conclusions from small, flawed data sets, it is not "science."

  3. Rodrigo:

    My only criticism for the video is that when it discusses the differences between the Northern and Southern hemisphere temperature rise, you don't factor in that the south has much more water and that might be slowing the temp rise.
    Still, killer video.

  4. AlgiL:

    For better understanding: What has been causing What; would it not have been prudent to review observed temperature data in more detail, e.g. differentiating between winter and summer, than it has been done in the section “The short view (100 years)”? It could draw a complete different picture on anthropogenic forcing, as it has been discussed by: . Another example is the four decade global cooling that started in winter 1939/40 with a ‘bang’, with extreme winter temperatures all over the Northern Hemisphere, but particularly the coldest winter in North-western Europe for more than 110 years, see: . Not only IPCC’s, but also sceptic’s claims, as by Richard Lindzen, would get weight, if they clearly could explain the two major climatic shifts during the 20th Century, the sudden commencement of (1) Arctic warming in winter 1918/19, and (2) Global cooling in winter 1939/40.

  5. markm:

    Bearster: Satellite measurements take an average over the whole atmosphere. They are free from the urban heat island effect, and show some warming, but they only started in 1979 and it's quite clear that the late 1970's were unusually cold. IOW, any measurement series starting in the 70's could be just showing one part of a several-decade cycle, similar to looking at temperatures from February to August and seeing a warming trend...

    Over a longer term, records of rivers being frozen over, etc., clearly show a warming trend from the early to mid 1800's to the 1930's, but also clearly show the "Little Ice Age" where Europe and presumably all the mid to high latitude areas of the world cooled down for several centuries, and then started to recover in the 1800's. (AFAIK, Europe was the only part of the world where good enough records have been found for 1300-1800. Has anyone searched the Chinese records? OTOH, if the effect happened mainly at higher latitudes, China might have missed most of it. It should have affected Mongolia and Siberia, driving hungry barbarians into Chinese territory, but the Chinese have always had to beat back hungry barbarians, and I doubt they kept a good count of barbarian incidents that would show the effects...)

  6. Oliver Postgate:

    The Coyote can howl and wind himself into pseudoscientific knots to show us all that what is there isn't there after all. I can see the ice-caps retreating. I can see that snow no longer covers the mountains. I can see that the poor of the world who rely on melt-water for their crops will die when it stops flowing. I can see the desert moving across Africa. I can see the Amazon basin drying away. I can hear the fish moving northwards.
    There is one simple scientific truth that Coyote ignores. It is this: where there is even a possibility that the changes that are happening could lead to the ending of life on earth, (as they have before), there is no case for anything but worst-case thinking and action. If we take it and were wrong, we shall be alive. If we talk ourselves out of it and it happens, our children are dead dry meat. You decide. It is your world. I shall be long dead.

  7. cookie:

    'I can see that the poor of the world who rely on melt-water for their crops will die when it stops flowing.'

    Don't worry, Oliver. The World isn't running out of poor people just yet for you to patronise. Why, there are 600 million more of them today than there was at the start of 2000. Just check out the population stats to settle your worrying heart. Oh, but, these people are all contributing to the population explosion crisis ... well, I am sure you can resolve these contradictory concerns to your own satisfaction.

    I am confident that Humanity won't die out just yet. We have survived predators, 'natural' climate changes and even the 'consensus' of socialism amongst our 'intellectual elite' (elite in their own minds, at least).

    Onwards and upwards!

  8. nobwainer:

    I like this tactic the alarmist's use....spend a heap now which may be a terrible waste or possibly pass on a dying world to your children. The science to cool the earth and scrub out the co2 if needed seems to already exist, probably costing much less than a carbon trading scheme. i have seen the mighty flaws in the science, i would rather wait and see and spend later.