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Mar 4, 2011

The Australian Academy of Science: what is climate change?

The period for estimating climate is usually 30 years or more, long enough to sample a full range of weather.

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This is an extract from The Science of Climate Change — Questions and Answers, published by the Australian Academy of Science and distributed to members of parliament, every local government authority in Australia and every Australian high school, in August 2010. Crikey will be running a series of extracts, including canvassing common myths.

Climate change is a change in the average pattern of weather over a long period of time Climate is a statistical description of weather conditions and their variations, including both averages and extremes. Climate change refers to a change in these conditions that persists for an extended period, typically decades or longer.

Weather variables such as temperature and rainfall fluctuate naturally (see Box 1). These changes in weather from day to day, between
seasons, and from one year to the next, do not represent climate changes. The period for estimating climate is usually 30 years or more,
long enough to sample a full range of weather.

Climate can be defined for a particular place or region, usually on the basis of local rainfall patterns or seasonal temperature
variations. Climate can also be defined for the entire Earth. For global climate, a key variable is the average surface temperature.

Sustained and truly global changes in average temperature require some global heating or cooling influence such as variations in heat output by the Sun, changes to the Earth’s orbit around the Sun, changes in cloudiness, changes to the extent of ice on Earth’s surface, or changes in greenhouse gas concentrations in the atmosphere.

Identifying climate change that is truly global in extent requires simultaneous observations from a network of locations around the world (see Question 3). Such a network of instrumental observations has only been available since the second half of the 19th century. Climate changes that occurred before this time can be identified by reconstructing records from climate-sensitive indicators like ocean sediments, ice-cores,
tree rings and coral reefs.

Greenhouse gases play an important role in determining climate and causing climate change Greenhouse gases include water vapour, carbon dioxide (CO2), methane, nitrous oxide and some industrial gases such as chlorofluorocarbons (CFCs). These gases act like an insulating blanket, keeping the Earth’s surface warmer than it would be if they were not present in the atmosphere.

Except for water vapour, the atmospheric concentrations of all of these gases are being directly influenced by human activities (see Question
4). Once released into the atmosphere, many of these gases remain there for a long time: in particular, a significant fraction of CO2 emissions remains in the climate system for hundreds to thousands of years.

Water vapour is an important greenhouse gas but it is not like the greenhouse gases affected directly by human activities. Its concentration in the atmosphere is controlled by the climate itself, rather than by human activities.

Water vapour therefore reacts to, and amplifies, climate change caused by other factors (see Box 2 and Figure 1.1). The effects of changing greenhouse gas levels on climate can be distinguished from the effects of other factors such as changes to the Sun’s radiation. These different causes lead to different patterns or “fingerprints” in the resulting climate changes, which assist in identifying the cause of observed changes.

For example, increases in solar radiation would be expected to warm both the upper and lower parts of the atmosphere and result in days warming more than nights. On the other hand, increases in greenhouse gases would be expected to result in a cooling, not a warming, in the stratosphere (the layer of the atmosphere above 15 km elevation), and cause nights to warm more than days. The observed patterns of change
more nearly match those expected from increasing greenhouse gases.

There are close connections between global temperature, atmospheric water vapour, the extent of polar ice caps and levels of greenhouse gases (GHGs) in the atmosphere. When one of these is disturbed, the others react through processes that amplify the original disturbance until
a new, different climate equilibrium is reached.

In the glacial cycles over the past million years, the disturbance came from fluctuations in the Earth’s orbit around the Sun (grey box in upper diagram). This caused temperatures to change (green box), in turn inducing rapid changes in water vapour (left blue box), and much slower
changes in ice caps (right blue box) and greenhouse gas levels (orange box), which together amplified the temperature change.

In modern climate change, the disturbance comes from human-induced changes in atmospheric CO2 and other greenhouse gas levels (grey box in lower diagram). In both cases, the disturbance is amplified by similar reinforcing processes.

The Australian Academy of Science, which represents Australia’s foremost scientists, provides scientific advice to policy makers and promotes excellence in Australian science, has devoted considerable resources to untangling the science of climate change and presenting it in a simple and easily understood format.

The full report can be downloaded here for free.

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67 comments

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67 thoughts on “The Australian Academy of Science: what is climate change?

  1. JamesH

    DanR, if you really want to know why water vapour does not override the effect of CO2, I suggest you check this section and this section of Spencer Weart’s The Discovery of Global Warming. In a nutshell, the absorbtion bands of H2o and CO2 do not always overlap, particularly not in the top layers of the atmosphere where the pressure is low there is much more CO2 than H2O, and it is the absorbtion and emission of the top layer which determines the temperature of the whole system.

  2. JamesH

    You’ve misunderstood me DanR; I am talking about absorption from below, as you’d know if you’d checked the links I provided.

    What do you think the heated water and CO2 in the first 30 metres does? It doesn’t just sit there. Convection carries a lot of that heat up, and eventually excited molecules reradiate, in random directions, including upwards. Heat is thus transferred upwards to the next layer of the atmosphere, where it is absorbed and reradiated randomly again, and so on, until it eventually reaches the top layer, where it is radiated either into space (and thus lost) or back down again. The more CO2 is in that top layer, the higher the percentage of IR which is re-radiated downwards.

    Alternatively, Spencer Weart’s wording:
    “What happens to infrared radiation emitted by the Earth’s surface? As it moves up layer by layer through the atmosphere, some is stopped in each layer. (To be specific: a molecule of carbon dioxide, water vapor or some other greenhouse gas absorbs a bit of energy from the radiation. The molecule may radiate the energy back out again in a random direction. Or it may transfer the energy into velocity in collisions with other air molecules, so that the layer of air where it sits gets warmer.) The layer of air radiates some of the energy it has absorbed back toward the ground, and some upwards to higher layers. As you go higher, the atmosphere gets thinner and colder. Eventually the energy reaches a layer so thin that radiation can escape into space.

    What happens if we add more carbon dioxide? In the layers so high and thin that much of the heat radiation from lower down slips through, adding more greenhouse gas means the layer will absorb more of the rays. So the place from which most of the heat energy finally leaves the Earth will shift to higher layers. Those are colder layers, so they do not radiate heat as well. The planet as a whole is now taking in more energy than it radiates (which is in fact our current situation). As the higher levels radiate some of the excess downwards, all the lower levels down to the surface warm up. The imbalance must continue until the high levels get warmer and radiate out more energy. As in Tyndall’s analogy of a dam on a river, the barrier thrown across the outgoing radiation forces the level of temperature everywhere beneath it to rise until there is enough radiation pushing out to balance what the Sun sends in.”

  3. JamesH

    DanR: There is no such thing as “degraded” infrared radiation; atoms emit at the same wavelength they absorb. This is very basic quantum mechanics – if this wasn’t the case, lasers wouldn’t work, and neither would spectroscopy. Try reading this wikipedia page on emissions spectrums: http://en.wikipedia.org/wiki/Emission_spectrum

    Nor is there any doubt that CO2 is the relevant gas in our atmosphere; direct measurement of IR from below and above (satellites) shows IR emissions in the CO2 bands, which are distinct from the water vapour bands.

    No-one is disputing that water vapour acts as a greenhouse gas, but it and CO2 are not competing to absorb energy; their absorption does not overlap.

    Bird: Incoming radiation is at a different wavelength from outgoing, so CO2 doesn’t block as much on its way in as on its way out.

  4. birdsnewworld

    Let me illustrate how backwards that is. Many leftists are press-ganging in the bad science of “global warming” so that they can promote globalism, ration energy, control all aspects of our lives, and so forth. Whereas you seem to be press-ganging in the even worse science of the big bang as a way of countering the global warming fraud. So where is the search for TRUTH in all this press-ganging?

    The problem with 20th century physics has been to do with bad epistemology and the cult of personality. The big bang theory is based on the Hubble doctrine. And the Hubble doctrine goes like this: Since doppler causes red shift ONLY doppler causes red shift ..

    Now this is not only illogical. Its not only wrong. It cannot be right, given the particle soup that we take to be space.

    The big bang started off bad, since one ought not build on one line of evidence. You need to have at least three lines of evidence to build on. But the big bang theory continued to get more ridiculous as the evidence refuting it rolled in. The other problem with methodology was the failure to have competing theories on the fly all the time. Since when the evidence against the big bang rolled in, it would then have been recognised as such. The Hubble doctrine itself was debunked in 1968.

    You can debunk the big bang yourself just be noting that there are stars and galaxies in all directions, going as far back as the technology allows. Whereas had there been a starting location, when we got back a certain way, the galaxies would be in one direction only. Thats the big bang finished as a theory right there. But public servants don’t know what a refutation is any more.

    When the news came in that the universe was accelerating in its expansion …. this ought to have been taken as a refutation. But no. They just keep building on earlier mistakes. Thats the public service for you.

  5. birdsnewworld

    “What current useful models are there?”

    There’s nothing that the mainstream would consider without a lot of appalling name-calling. But let me give you an idea of what to expect:

    Once you have given up on certain bad mental habits it takes a while for the mind to shift so as to take in all the implications of a universe without a creation myth. The public servants have the bad habit that things can be created on the instant, rather than by complex processes, and over time. If only it were true around the factory. So they have matter showing up ex-nihilo and expanding outwards at trillions and gazillions of times the speed of light. All embarrassing idiocy of course.

    But consider the idea of the photon. It also gets created for no reason, and hot-tails it out of wherever it is at the speed of light.

    Supposing you were to put all this nonsense behind you. You face the uncomfortable idea that the matter is here. But since any rational understanding of how it got here, would have it being converted and staying put, then any better theory must have matter being created ON-LOCATION.

    We look out at the universe and we see that there is a lot of space and then great accumulations of matter. We pretty much have to accept that the new matter is being created WHERE IT ALREADY IS. And that this is an ongoing process. Otherwise we split time into an age of miracles and an age of the new prosaic world.

    Now we would say that the matter is being created where it is but this is really CONVERSION. Since once we get rid of spooky-action-at a distance ……. for gravity to operate all matter in the galaxy must be connected. Since it is manifest that gravity propagates instantaneously and does not wait on light speed.

    So we then would see that we could split matter into that matter which is locked into the gravitational web, and that matter which isn’t. And that matter which isn’t has to be presumed the majority by far, and to be barely interactive. So what must be happening is matter must be being converted in moons, planets and stars, from barely interactive matter, to matter that is being brought into the gravitational network and that readily interacts or impinges on other like matter.

    20th century physics has banished the natural philosopher and has replaced him with all these maths-boy 101 Raiman types.

  6. danr

    So it seems that the core of what you are suggesting is your second last para.

    Is this analogous to the concept of dark matter which is assumed to be present.
    This dark matter, accounting for effects seen but not explicable ules DM is assumed present?

    In trying to read Stephen Hawking’s book what I got was lot of basic Big Bang stuff and a quick jump to mathematical models which were difficult for me to relate to.

    I may not be terribly smart but I have an inbuilt distrust of models which don’t seem to be clear even to the modeler. The models seem to exist to allow the modeler to display his mathematical prowess rather than shed light on the current properties of the Universe.

    In one sense there is a great deal of good in exploring concepts. Sometimes it pays off sometimes it doesn’t. The questions surrounding the origin and current state of the universe are very difficult to explore.

    Translating this scientific overview to AGW is interesting.

    The basic science of AGW by comparison is very pedestrian, embarrassingly so .

    The problem is the confusion created by the vast number of chemical and physical interactions in the CO2 – biosphere temperature question.

    They are easily quantified if you take the trouble, but cause embarrassment to the AGW Cause if taken into account.

    Why would any scientist on a grant take the trouble to do the full analysis when they can get away with doing work on one small element of the process.

    There are reasonable CO2 mass balances done on many sources and sinks of CO2 but you will find nobody wants to integrate the parts into a complete whole.

    The reason is that such an analysis shows the human produced component of CO2 to be disappointingly small against the real sinks and sources. The human effect on CO2 activity in the atmosphere is undetectable.

    This is not good science but a very interesting study in Group Behaviour patterns. It’s the universe of politics at its finest.

  7. birdsnewworld

    “Don’t fixate on the public service as the source of most breakthroughs in physics, Bird, it certainly isn’t.”

    The modern era has science workers talking like lawyers and bureaucrats. The above statement deserves special scrutiny. Its lawyer-talk in that its literally true but deeply troubling.

    Meski we are not talking about breakthroughs here. The global warming racket is hardly a breakthrough. Nor is that outdated and debunked special relativity religion. Nor that fantasy mirroring the doctrine of the holy trinity ……. particle/wave duality. Not that there is anything wrong with the doctrine of the holy trinity. But its theology. The doctrine of the holy trinity is not science, properly-considered. And the ultimate embarrassment of the “big bang” is hardly a breakthrough.

    If by “breakthroughs” you mean “bad science” and if you meant to say that bad science comes from everywhere, then I’m in agreement. But the notable thing about the public service is that it grabs onto, promotes, reinforces, rewards, and locks in bad science.

    Good science impacts on our lives in big ways. Its dividends are there for all to see. Supposing you take a serious scientist like Faraday. Rubbing metal balls with rabbits fur and demonstrating the wonders of static electricity?

    Was there any reason to believe that this electricity jive would amount to much when he was making these demonstrations??? To the untrained eye no. But it was good science and with good science in time there will be major consequences from it.

    Everywhere we see bad science getting in the way of potentially positive benefits, known and unknown. Bad science sucking up all the oxygen. Wasting the potential of many higher IQ kids in the population. Bad science demonising all those who can see through it. Alerting us to dangers that aren’t there, and making us blind to authentic catastrophes on the horizon.

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