What natural cycle are deniers talking about?

I've asked similar questions before and have never recieved an adequate response that answer the question. Let's try again seeing there have been increasing claims pointing to natural cycle being responsible for the earth's increase in temperature..

We hear over and over "its a natural cycle" when deniers are trying to spread their disinformation about anthropogenic global warming. The IPCC states in the AR4 Chap.2 Page 131-

"The combined anthropogenic RF is estimated to be +1.6

[–1.0, +0.8]2 W m–2, indicating that, since 1750, it is extremely

likely3 that humans have exerted a substantial warming

influence on climate. This RF estimate is likely to be at least

five times greater than that due to solar irradiance changes. For

the period 1950 to 2005, it is exceptionally unlikely that the

combined natural RF (solar irradiance plus volcanic aerosol)

has had a warming influence comparable to that of the combined

anthropogenic RF."

(the term “Exceptionally unlikely” is the highest level of confidence that the IPCC assigns. It means they believe that there is < 1% probability that the science is inexact. AR4 Uncertainty Guidance Note for the Fourth Assessment Report)

And on page 132 of the same chapter-

"The direct RF due to increases in solar irradiance since 1750

is estimated to be +0.12 [–0.06, +0.18] W m–2, with a low level

of scientific understanding. This RF is less than half of the TAR


— The smaller RF is due to a re-evaluation of the long-term

change in solar irradiance, namely a smaller increase from the

Maunder Minimum to the present. However, uncertainties in

the RF remain large. The total solar irradiance, monitored from

space for the last three decades, reveals a well-established cycle

of 0.08% (cycle minimum to maximum) with no significant

trend at cycle minima."

In other words, it's not the sun. In the back of this one chapter you will find seventeen pages of references to studies that have passed peer review.

So, if it's not the sun what is this mysterious natural cycle that deniers claim to be at work warming the planet.

To answer this question properly you will need to back up your claim with a reference to peer reviewed studies. If you don't back up your claims then your answer would not be valid and considered nothing more than pseudo science designed to mislead.


9 Answers

  • 1 decade ago
    Favorite Answer

    Ah yes, the beauty of the "natural cycle" argument is that it's all-encompassing. You can consider solar effects, the PDO, ENSO, volcanoes, etc. all to be "natural" (although some of these are not cyclical). Basically they're betting on "not anthropogenic", which is ironic, because the accuse AGW proponents on betting on "not natural".

    The physics supports anthropogenic effects. As your quotes note, the radiative forcing (RF) from anthropogenic greenhouse gases dwarfs all other radiative forcings over the past 30+ years. It's not that we're simply ruling out natural effects and then concluding "well, the only thing left is anthropogenic!", it's that the physics supports the anthropogenic warming theory.

    There have been a number of proposed "natural" effects for the recent warming. The reason there are so many is that "skeptics" can't settle on any one effect, because none are supported by the physical evidence. As you note, the Sun has been conclusively ruled out. The PDO can't cause long-term climate change because it's cyclical. Since 1950 there's been one warm and one cool PDO cycle of equal and opposite strength, yet the planet has warmed rapidly over that period.

    The "1,500 year cycle" mentioned in another answer is the D-O cycle. There are a number of flaws with this theory, the main one being that the current warm period, MWP, and Roman Warm Period were each about 1,000 years apart. The D-O cycle happens every 1,400-1,500 years. Anyone who's taken basic arithmetic can see the flaw here. Then there's the galactic cosmic ray theory, which has been torn to shreds by many recent peer-reviewed studies.


    Nobody has been able to propose a feasible "natural" cause for the recent warming, and AGW is supported by physics. It's really as simple as that.

    *edit* Jim's comment about sticking fingers in ears and going "Lalala" is exceedingly ironic since he then cites Spencer's cherrypicking of Loehle's highly-flawed temperature reconstruction - which couldn't even pass peer-review - over the many other global temperature reconstructions with much more data and much different results.



    If that kind of ridiculous cherrypicking isn't sticking their fingers in their ears and going "Lalala" then I don't know what is.

  • 4 years ago

    Well, when all known variables have been allowed for, and CO2 has been ruled out on ideological grounds, whatever is left is the natural cycle! We may not be able to explain it but that doesn't matter, we just know it's there! Isn't it great to know that, when logic and reason fail, there is something to fall back on; something that will never let you down.

  • 1 decade ago

    I think when they say "natural cycles" they really mean unattributed non-anthropogenic variations. They don't mean cycles, as such, because cycle implies periodicity, and if something was periodic we'd probably have an explanation for it already--like orbital variations or solar cycles.

    I've never seen a good "skeptic" explanation for why the greenhouse effects of CO2 should be ignored, since they're based on well-established science. The infrared absorption spectrum of CO2 is well-known and can't be dismissed away by making a reference to natural cycles.

  • Tomcat
    Lv 5
    1 decade ago

    Perhaps its the inverse of the natural cycle that has caused the Earth to cool for the last several years. After all if a poorly understood natural cycle can cause the Earth to cool, contrary to what climate models have predicted, the only logical conclusion would be that a poorly understood natural cycle could also cause the Earth to warm.

    And as far as your simplistic explanation of TSI and it's impact on climate, UV irradiance flucuates much more than TSI and directly affects the composition of the upper atmosphere. Perhaps in about 2 or 3 more decades there will be enough data have a better understanding of Earths climate, but for now back of the napkin calculations about TSI proxies and their long term implications of past and future climate are purely hypothetical scenarios.

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  • eric c
    Lv 5
    1 decade ago

    To say it has to be co2 because it cannot be the sun is bad science and logic. You also have to prove it is co2. It also cannot be co2 because co2 is increasing at a faster rate than what the models are projecting, but yet temperatures have remained the same.

    It cannot be co2 because the models project a hot spot (or a signature). It says that if it is greenhouse warming the troposphere has to warm at a faster rate than ground temperatures. But in fact it has been warming at a slightly lower rate. In any other areas of science when you make a prediction based on climate models and that prediction does not turn out correct that would put serious doubt on the theory. That is all areas of science accept climate science.

  • JimZ
    Lv 7
    1 decade ago

    Obviously,you are not interested in the truth. You stick your fingers in your ear and go Lalalalaalala. If you can read a graph, this graph clearly shows how the climate has warmed and cooled over the last 2000 years. It matches historical records and includes reliable climate proxies.


    Humans didn't cause the cooling 1000 years ago

    Any scientist would agree with that

    Humans didn't cause the warming that began roughly 400 to 300 years ago.

    Again any scientist would agree with that.

    Why do you insist on believing that we have caused the warming since then?

    What is the point?

    You believe because it is poltically expedient for you. It fits your world view. Facts don't play an important role in your thinking.

  • 1 decade ago

    If you believe in global warming, that is your right. I just wonder what you or anyone or everyone else think you can do to stop it?

    The only way would be to get rid of all the cars in the world. Not just the Western World, but all countries. Think that is going to happen? I don't think so.

    Then you have to kill off over 1/2 of the population, quit growing food, get rid of all livestock, quit using electricity, ban all computers, cell phones, and game boys. Are you and all of you who believe in global warming prepared to do that? I don't think so.

    The quotes you have given is the pseudo science designed to mislead.


  • 1 decade ago

    no idea, I've never said that.

    and anyway, why should skeptics prove that temp trends / cycles are natural.

    prove they aren't.

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