The IPCC 5th Assessment Report: The authors speak

A slide from the first talk of the Royal Meteorological Society Event.

A slide from the first talk at the Royal Meteorological Society meeting discussing the 5th Assessment Report of the Intergovernmental Panel on Climate Change. Is it really unequivocal?

Last week I attended my first meeting of the Royal Meteorological Society: it was a Wowser!

Many of UK’s leading climate scientists gave 15 minute précis talks describing the key results from the chapters of the IPCC 5th Assessment report on which they were authors.

  • The slides used in the précis talks and audio recordings of each talk can be found here.
  • The chapters of the IPCC assessment report can be found here.

I went with the aim of getting answers to three questions:

  • How good are climate models?
  • What does the data look like on sea level?
  • Why is Antarctic Sea Ice increasing in extent?

I will cover these questions in future articles, but here I would just like to comment on one of the first slides (reproduced above) stating baldy that there was simply no doubt that the Earth’s climate had warmed.

I found this interesting in the of a light of comment by climate skeptic Judith Curry who quotes another web-site stating that ‘Freezing is the new warming

Or try refuting global warming. Temperatures have stopped warming for more than a decade? That’s just a temporary “pause” in the warming that we just know is going to come roaring back any day now. Antarctic ice is growing? That’s actually caused by the melting of ice, don’t you know. A vicious cold snap that sets record low temperatures? That’s just because the North Pole is actually warming. So if the winter is warm, that’s global warming, but if the winter is cold, that’s global warming, too. If sea ice is disappearing, that’s global warming, but if sea ice is increasing, that’s global warming.

Now we can see what they mean when the warmthers say that global warming is supported by an ironclad scientific consensus. The theory is so irrefutable that it’s unfalsifiable!

Which is to say that it has become a cognitive spaghetti bowl full of ad hoc rationalizations, rather than a genuine scientific hypothesis. 

As the meeting progressed I reflected on the possibility that these scientists – myself included – were involved in some kind of collective delusion. Was that really believable?

I decided not, but I thought it was a question worth asking, and answering clearly. So here is the answer.

There are three key facts which are beyond any reasonable doubt.

  1. The concentration of carbon dioxide in the Earth’s atmosphere is increasing.
    • This has been measured directly for more than 50 years and historical values can be inferred from ice cores in Greenland and in Antarctica.
  2. The reason for this increase is our burning of fossil fuel
    • We can detect the isotopic signature of ‘fossil’ carbon and the reduction in oxygen concentration cause by the combustion.
  3. Carbon dioxide increase the ‘radiative forcing’ on the Earth’s climate system.

What is unknown is precisely what the consequences of the warming will be, or how rapidly they will become apparent. The Earth’s climate system is complex, and it does not repond in a simple way.

To use a mechanical analogy, if one pushed a rigid sphere one could predict how it would respond. But if one pushes a spherical jelly, then it will still move, but there will be many wobbles and its precise trajectory is not easily predictable.

So if we look at Curry’s criticisms one by one:

  • Temperatures have stopped warming for more than a decade?
    • A decade is not a long time in Climate Studies, and this just doesn’t mean anything yet. Many other indicators of climate change have continued to change.
  • Antarctic ice is growing?
    • As I mentioned previously – Antarctic Sea Ice is growing slightly. I don’t know why and when I ask specialists I get answers that seem handwaving. However Arctic Sea is shrinking dramatically, and this is well understood and predicted by climate models.
  •  A vicious cold snap that sets record low temperatures?
    • Curry here talks of North America: globally it has not been particularly cold. But one cold winter is weather not climate.

Predicting the future climate of Earth is almost as hard as predicting the weather, and in fact predictions from the 1980s are shaping up pretty well.

So as time moves on, and our understanding of the basic principles that determine climate improves, this only reinforces our understanding that human-kind’s emissions of carbon dioxide are affecting the Climate. There really is no doubt about it.

I was impressed that at the meeting there was complete openness about which data were well-understood, and which models worked well and which worked not so well. Hearing this open discussion is one of the most convincing signs of a research community that was very much focussed on reality, which is never simple.

==============

Thank you to Variable Variability for the quote from Judith Curry’s site.

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2 Responses to “The IPCC 5th Assessment Report: The authors speak”

  1. FK Says:

    You comment that 10 years is not a long time…I agree…neither is 50 years! I agree that the CO2 levels are rising, but there is no proof it is from burning fossil fuels…there are many other reasons i.e. deforestation, etc…Also, the ice core samples show that CO2 levels have risen and fallen a number of times over several thousand years…There is no proof that CO2 concentrations, which have fluctuated from 340/ppm to 400/ppm actually cause global warming! What is the mechanism? Meanwhile, global alarmists make millions on the donations of the frightened world…

    • protonsforbreakfast Says:

      Interesting points but you are quite wrong. Specifically, there is abundant proof that the carbon dioxide arises mainly from fossil fuels.
      1. There is a corresponding decline in the concentration of oxygen in the atmosphere.
      2. The isotopic signature of the carbon on the carbon dioxide indicates a fossil origin (i.e. much older than 5000 years since it had been in the atmosphere)
      SO there is absolutely no doubt at all about the source of the carbon dioxide in the atmosphere.
      3. Additionally you have misquoted the historical variability. Over the last 400,000 years levels varied between about 180 ppm and 280 ppm and never exceeded 300 ppm. The value now is approaching 400 ppm and rising.

      I think there is a fair case that the world should be alarmed about this.

      References
      ==========
      1. http://www.esrl.noaa.gov/gmd/obop/mlo/programs/coop/scripps/o2/o2.html
      2.http://www.esrl.noaa.gov/gmd/outreach/isotopes/
      3.http://en.wikipedia.org/wiki/File:Vostok_Petit_data.svg

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