We Are 95% Confident in a Meaningless Statement

Apparently the IPCC is set to write:

Drafts seen by Reuters of the study by the U.N. panel of experts, due to be published next month, say it is at least 95 percent likely that human activities - chiefly the burning of fossil fuels - are the main cause of warming since the 1950s.

That is up from at least 90 percent in the last report in 2007, 66 percent in 2001, and just over 50 in 1995, steadily squeezing out the arguments by a small minority of scientists that natural variations in the climate might be to blame.

I have three quick reactions to this

  • The IPCC has always adopted words like "main cause" or "substantial cause."  They have not even had enough certainly to use the word "majority cause" -- they want to keep it looser than that.  If man causes 30% and every other cause is at 10% or less, is man the main cause?  No one knows.  So that is how we get to the absurd situation where folks are trumpeting being 95% confident in a statement that is purposely vaguely worded -- so vague that the vast majority of people who sign it would likely disagree with one another on exactly what they have agreed to.
  • The entirety of the post-1950 temperature rise occurred between 1978 and 1998 (see below a chart based on the Hadley CRUT4 database, the same one used by the IPCC

2013 Version 3 Climate talk

Note that temperatures fell from 1945 to about 1975, and have been flat from about 1998 to 2013.  This is not some hidden fact - it was the very fact that the warming slope was so steep in the short period from 1978-1998 that contributed to the alarm.  The current 15 years with no warming was not predicted and remains unexplained (at least in the context of the assumption of high temperature sensitivities to CO2).  The IPCC is in a quandary here, because they can't just say that natural variation counter-acted warming for 15 years, because this would imply a magnitude to natural variability that might have explained the 20 year rise from 1978-1998 as easily as it might explain the warming hiatus over the last 15 years (or in the 30 years preceding 1978).

  • This lead statement by the IPCC continues to be one of the great bait and switches of all time.  Most leading skeptics (excluding those of the talk show host or politician variety) accept that CO2 is a greenhouse gas and is contributing to some warming of the Earth.  This statement by the IPCC says nothing about the real issue, which is what is the future sensitivity of the Earth's temperatures to rising CO2 - is it high, driven by large positive feedbacks, or more modest, driven by zero to negative feedbacks.  Skeptics don't disagree that man has cause some warming, but believe that future warming forecasts are exaggerated and that the negative effects of warming (e.g. tornadoes, fires, hurricanes) are grossly exaggerated.

Its OK not to know something -- in fact, that is an important part of scientific detachment, to admit what one does not know.   But what the hell does being 95% confident in a vague statement mean?  Choose which of these is science:

  • Masses are attracted to each other in proportion to the product of their masses and inversely proportional to the square of their distance of separation.
  • We are 95% certain that gravity is the main cause of my papers remaining on my desk


  1. sean2829:

    It looks like the arguments will break down to causes and pauses. If the latter cannot be explained there will be no credibility with respect to attribution of the former.

  2. Rod Tidwell:

    It is 95% certain that this report will not stop the flow of public money to the perpetrators of this junk science.

  3. jdgalt:

    Does it count as meaning the increase really was caused by man, if Mann just made that "fact" up?

  4. Gil:

    By that graph the 1945 to 1975 period was no global cooling but a flat pause that was still warmer than everything before 1930.

  5. Gil:

    What, you can't see an upward trend? Don't forget that pause was just after WW2 - industries were smashed, great many lives lost as well much particulates in the air from all the bombings. An interesting support for AGW is that there are global cooling periods when there's been depopulation events due to war and/or epidemics.

  6. skhpcola:

    I'm happy to see that Warren has apparently--by the lack of semi-retarded posts on the topic--abandoned the jihad that he was on a couple of years ago in which he was an advocate of carbon taxes. Those, along with the entirety of the anthropogenic climate change fraud, were nothing but window dressing for the ploy by ecofascist bastards to snag more power and control over the hoi polloi.

  7. Benjamin Cole:

    What always gives me a chuckle is the certitude that oceans levels are rising due to man, or that they cannot rise.

    Ocean levels have been rising ever since the end of the last Ice Age, and pretty steadily for the last 16,000 years.

    If you own oceanfront land, you will be under water someday. We are up 60 meters in last 10,000 years. Another few meters would be nothing.

    As a taxpayer you should be concerned that the federal government is underwriting flood insurance for five million coastal dwellers, especially Florida and Texas. The Fed don't even make people build on stilts, as a condition of insurance.

  8. sean2829:

    Have you ever thought that maybe global cooling events might lead to war and depopulation associated with loss of basic staples in agrarian economies? As far as the latest pause goes, several meteorologist predicted 10 years ago warming would stop when the PDO flipped. The well funded climate modelers predicted warming would continue un-abated. The latest pause is not associated with a depopulation event. Chinese sulphur emission have also been blamed for the pause but more cooling is taking place in the southern hemisphere. Michael Mann threw a monkey wrench in climate understanding by leaving the impression that the climate is flat and stable rather than a roller coaster where natural cycles ramp temperatures up and down.

  9. morgan.c.frank:


    the great irony is that the climate models all have confidence intervals, and actual climate has failed to line up with them.

    by the IPCC's own data, they are 95% confident that the models are wrong.

    this is especially glaring as those models were based on considerably lower levels of co2 that actually prevail.

    even the graphs leaked from ipcc ar5 (forthcoming) confirm this.


    when you get a worse than worse case input and a better than best case output, guess what? your model is junk.

  10. Joe_Da:

    The earth's temp has always fluctuated up and down for milenuims - that was until 2000 years ago when suddenly the earth temperature became extremely stable. This coincided with the birth of christianity and God was pleased. Now God is displeased because man is polluting the earth, So God has allowed mother nature to occur naturally to pushing temps up and down to punish man (Mann). Does Mann not remember the Holcene days when God made Noah built the ark.

    That in a nutshell is the scientific basis of AGW - and what the 97% of climate scientists agree with.

    PS my apologies for any comparison to Genesis.

  11. Zachriel:

    "It is extremely likely (>95%) that human influence on climate caused more than half of the observed increase in global average surface temperature from 1951 to 2010."

  12. Gil:

    One wonders where "pauses" come from that only deniers can find? Graphs keep showing an upward yet the moment the graph flattens a little suddenly "global warming is over!"

  13. Rik:

    Temperature is down. The long term trend is down. The previous warm periods of the holoscene was warmer than today by all resonable estimates. We are still living in an interglacial period in an ice-age.

    If "most of the warming since the end of the war" (when emissions started to rise) is due to humans that still doesn't mean anything alarming at all. Most of 0,4° can be 0,2°C, over 60 years when we burnt half of the known reserves. And that is not counting the 50% overestimation of warming (it is related to local industrial activity when it should not if properly measured). And that is not counting that the solar activity was high during the 20th century, implying that at least some of the warming was due to solar activity.

    If a rise from 280 ppm CO2 to 400 ppm gave at the most 0,04° per decade, should we be sufficiently alarmed to transfer all this wealth to connected corporations and dictators in the poor world?

  14. JoshK:

    On another note, I was just reading an op-ed in the NYT, Now they are using the term "climate deniers", Love it.

  15. Gil:

    Every graph shows the same thing: temperatures are consistently rising overall. The Libertarian opposite would have to gold prices - prices are going down but that okay because prices are going to always go back up again because we're still under an Orwellian government using fiat currency hence spend all your spare money on gold and silver that we just happen to be sellers of.

  16. Rob JM:

    Lol, you do realise that 0.2 deg C increase due to CO2 is different to the 1.2deg predicted don't you?
    You do realise that the little ice age was the coldest period since the younger dryas period over 11,000 years ago!
    150 years of warming is nothing compared to 4000 years of cooling.

  17. markm:

    Gil, you are trying to explain a 30 year long pause by citing conditions that lasted only a few years. The industries were re-built and world GNP increased far beyond pre-war levels by 1955. A few countries lost many lives in the war, but the rest of the world kept right on reproducing, so the overall effect was probably just a reduction in the rate of population increase - which was reversed as soon as the soldiers came home to their families. Particulates settle out within a year. So if these were the causes of the cooling that started during WWII, it should have ended between 1947 and 1955, rather than continuing until the late 1970's.

    If you want to make a case for war causing global cooling, see if you can correlate the Little Ice Age to Genghis Khan or Timur the Lame. These war leaders killed a noticeable percentage of the much smaller world population, in a period when populations generally did not recover as quickly. They followed a policy of destroying cities and converting farms to grassland that might have depressed CO2 production for centuries. The dates that I glean from casual research just don't match up well enough to convince me it's worth looking into deeper, but the start of the Little Ice Age is much less documented than its ending during the 19th Century..