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It's the sun
Climate's changed before
There is no consensus
Surface temp is unreliable
Models are unreliable
It's cooling
Ice age predicted in the 70's
Al Gore got it wrong
We're heading into an ice age
CO2 lags temperature
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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

  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.

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© John Cook 2008