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It's the sun
Climate's changed before
There is no consensus
It's cooling
Models are unreliable
Surface temp is unreliable
Ice age predicted in the 70s
We're heading into an ice age
It hasn't warmed since 1998
Antarctica is cooling/gaining ice
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We're coming out of an ice age

The skeptic argument...

There is no question the Earth has been warming; it is coming out of the 'Little Ice Age'. However, there is no credible evidence that it is due to mankind and carbon dioxide. We've been coming out of a Little Ice Age for 300 years. We have not been making very much carbon dioxide for 300 years. It's been warming up for a long time. The Little Ice Age was driven by volcanic activity. That settled down, so it is getting warmer (source: The Capital Times by Reid Bryson)

What the science says...

The notion that we're "recovering from an ice age" implies there's some natural temperature the planet reverts to. But for climate change to occur, it requires a forcing to drive it. The planet warms if it's absorbing more energy than it radiates. It cools if it absorbs less energy than it radiates. So what forcing caused Earth to warm from the 1800's until now. There are two major factors.

The main driving factor, particularly over the early 20th century, was the increase in solar activity which steadily rose from 1900 to 1940. Temperatures closely followed solar activity so that when solar levels steadied in the 50's, so did global temperatures. The correlation between solar activity and temperature ends in the 70's when a long term warming trend began for the next 30 years. Over this period, solar levels have remained steady.

The other predominant factor over the 1800's was volcanic activity. Volcanoes emit sulfate aerosols which reflect incoming sunlight, cooling the planet. High volcanic activity in the 1800's exacerbated the Little Ice Age, cooling the planet over several decades. When the sulfates were washed out of the atmosphere, the cooling effect was removed. While a lack of volcano activity may have played some part in early 20th century warming, it's had little impact on warming since 1970.

So the two driving causes of natural climate change over the past few centuries as we've emerged from the Little Ice Age, solar variations and volcanic activity, have had very little to do with the last 30 years of global warming.

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Comments

Comments 1 to 7:

  1. Your reasoning here makes me think you've got your mind on the atmosphere and not the oceans.

    Supposing we are cooling from about 5000 years back. The Holocene maximum being from about 8000 years ago to about 5000 years ago. And supposing we are cooling at about .25degrees Celsius per 1000 years. Superimposed on that is the ups in downs of solar activity but only as it makes itself be known via accumulated and decumulated joules imbedded in the ocean.

    From that perspective its very EASY to talk about "RECOVERING" from the little ice age. Very easy. And you wouldn't need any special forcing to recover. It would just have to be solar cycles strong enough to accumulate energy given the energy hasn't yet hit what it would be normally given normal solar activity.

    I mean this is not you being silly or anything. You are doing a pretty thorough job here. But the point is that the WPSM model is a light and air show and it only takes in account the imbedded planetary and oceanic heat in a peripheral way.
  2. Solar levels lag temperature changes on earth because the two are correlated correctly. Solar changes should, in fact, lag the corresponding temperature changes which if the solar model is correct should be significant cooling in the mid 21rst century.
  3. Re: "We're coming out of an ice age" does not actually relate to "the little ice age" as that is a misnomer. Technically it was a little glacation. The speculation of coming out of an ice age actually refers to the earth's 4th ice age (Neogene-Quarternary or Neogene-Holocene). This is considered by most to be an interglacial period but it may in fact be the ending of the 4th ice age. There is no set time limit to an ice age, the first three had very large variability, so we do not actually know how much longer it will stay cool.
  4. In support of my last statement I suggest viewing a chart that shows the last 5 million years. The trendline is clearly positive (with or without including the current warming which is short cycle).
  5. The cooling effect continued through the 1800's right up to around 1950-1960 when Clean Air Regs and the increased use of oil caused a reduction in the use of coal.
    During this period the UK and the US alone were burning coal at around 400mt/a (1800's) to 1200mt/a (1900's) producing a lot of particulates ans sulphates.
    I could posit that the 'appearance' of the GMT signal is due to the lowering of coal usage; it will be interesting to watch GMT as China burns more and more coal.
  6. Re #4

    In fact the evidence indicates that the temperature trend of the last 5 million years is negative.

    see for example:

    Lisiecki, L. E., and M. E. Raymo (2005), A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records, Paleoceanography, 20, PA1003.



    What data are you looking at that lends itself to an interpretation of a positive temperature trend??
  7. I think this response to the argument is both unfair and utterly inadequate.

    It is unfair, because it uses mocking language. No one says we are coming out on an Ice Age. No one thinks that. Rather, we are coming out of a relatively long cooling period, often called the "Little Ice Age."

    It is inadequate, because it makes no effort to explain WHY the Little Ice Age occurred or why it ended. Look, there is obviously a larger cycle here. We had the Medieval Warming Period, followed by the Little Age, followed by the modern warming period. Why is this cycle occurring? I do not have the slightest idea. Obviously, however, it is not being driven by mankind, one way or the other, except for (arguably) very recent times. So, if you want to argue that man's role is decisive, you have to show that recent times diverge dramatically from pre-existing patterns.

    But this post does not do that. Quite the opposite. Skeptics make the obvious point that the current warming trend (or rather, the 20 year warming trend that ended ten years ago) is NOT dramatically different from the pre-existing trend. In fact, it fits in neatly with the pre-existing trend.

    What is the reply? You say that the early 20th century warming was driven by the Sun, but the late 20th century warming was not. This is a very unsatisfactory answer.

    (a) What drove the warming from the 18th century onward? You say that, in the early 20th century, it was in the sun; in the late 20th century, it was CO2. What was it in the 19th century? Your explanations lose force, when you leave out such huge parts of the story.

    (b) The crux of your argument is the many-times repeated argument that, "We have had thirty years of warming that cannot be explained by anything else, so it has to be CO2." Well, that contention is obviously false. We had twenty years, followed by ten years of no warming. You reply, the ten years does not matter; it is just a statistical blip. Well, if we subtract the ten year blip from the thirty years you base your argument on, you only have twenty years of unexplained warming. But wait, ten years is a blip, which we wave away with our hand. So, your whole theory rests of a double blip, twenty years. By your own logic, twenty years is not a long enough period to draw any conclusions.

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