Is what we’re getting ‘weather’ or ‘climate’?

A jest that passes around the sceptical fraternity has it that when we have hot days, or a hot spell, that’s global warming, and it’s an example of ‘climate change’. If we have an unexpectedly cool spell, on the other hand, that’s just ‘weather’, and what you’d expect — natural variability of some kind,  no need to explain it, move on, nothing new here. Another quip has it that ‘climate’ is the average of ‘weather’. A third, from Melbourne, says that if you don’t like the weather, just wait a while, because it’ll change later in the day.

There is of course some truth in all of those little summaries. Climate is indeed defined generally as the average of weather. My Shorter Oxford gives the primary meaning of the word ‘weather’ as ‘The condition of the atmosphere (at a given place and time) with respect to heat and cold, presence or absence of rain etc.’ That’s pretty straightforward. The word comes from a long, long way back in the history of language, and the root is the Indo-European verb to ‘blow’: if you articulate the beginning of the word weather, you’ll see that you do indeed blow the sound out. The entries for the word both as a noun and as a verb take up more than a column of tiny print, so you can see it is an important word in our language.

Now buildings and other things ‘weather’, which means that they change over time, and also survive storms and other aspects of weather, which leads us at once to ‘climate’, which is a much more recent word, Greek in origin (the root is the verb to’ slope’). Its meanings point to places with characteristic weather (‘climes’), and to the prevailing weather there (what we have in mind when we speak of ‘hot countries’). The words ‘climatography’ and ‘climatology’ are coinages of the middle of the 19th century. The dictionary doesn’t mention ‘climate science’.

The climates of Singapore and Sydney are rather different, though each of them can have similar weather from time to time, and we all understand that. I mention all this fascinating historical stuff partly because I’m interested in it, and partly because it emerged a day or so in testimony given to a House Committee on the Environment in Washington given by an academic who was once the US Navy’s Oceanographer and senior climate person. His name is David  Titley, and this is what he said, in part:

I am frequently asked if a specific or extreme event (for example, typhoon Sandy, drought, snowstorm) is or is not “caused” by climate change. Frankly, that is the wrong question. It’s like asking someone if their childhood upbringing “caused” him or her to attend a specific college. It’s more useful to think of climate as the deck of cards from which our daily, specific weather events are dealt. And as the climate changes, so does our deck of cards. For every degree of warming, we add an extra Ace into the deck. So, over time, the unusual hands, like a Full House with Aces high, become more plausible – and more common – with time. 

It’s the deck of cards analogy that caught my eye. It sounds plausible, but then — isn’t it the opposite of the conventional view that climate is the average of weather? In that case the deck of climate cards is created by weather, and only those cards can be played, as it were. For example, Canberra where I live has never had a temperature of minus 40 degrees Celsius, so that card could not be part of the climate deck. But Canada’s capital city Ottawa certainly has had minus 40 degrees in winter, so that temperature is part of its climate deck. The more I thought about it, the more I thought that this senior climate person did not seem to be at the sharp end of his ship.

As I see it, weather, our daily fare, is what defines climate, not the other way around. And Dr Titley’s climate deck of cards is a fundamentally flawed concept. We don’t in fact add an Ace into the deck for every extra degree of warming. We mightn’t be having an extra degree of warming where we are. What if we were to have a degree of cooling? What then happens to the deck of cards? Altogether, I was disappointed in the way he gave his evidence. He used a quip that I have seen before, to the effect that ‘absence of evidence is not evidence of absence’, and while this sounds portentous (and precautionary) it is not, if you look at it closely. The fact that there is no evidence that little green men have secretly been bottling atmospheric carbon dioxide and transport it to Mars does not mean that they haven’t been doing so.

Much better and more factual evidence was given by two luminaries in the data-analysis world of climate, Dr John Christy and Dr Roger Pielke Jnr, and you can read summaries of what they said in Judith Curry’s recent Climate etc post, which also has links to the full testimony in each case.

Why bother with what is said in Washington? First, global warming is global by definition, so what people say elsewhere has relevance to us. Second, we have no equivalents much in Australia of these Congressional appearances, so they are valuable in their own right.

[Update: I came across another jest, this time from Mark Twain. ‘Climate is what we expect. Weather is what we get.’]

Join the discussion 13 Comments

  • David says:


    I do not think it makes sense, to look for a causal relationship between weather and climate, as they are one and the same. Out climate is simply the average of the weather, in much the same way that a forests is the average of the tress that growth within then. Stromlo forest is a pine forest because it is dominate by pine trees. Do trees cause forests or forests cause trees?

    • Mike O'Ceirin says:

      I am curious you say Stromlo forest is a pine forest being an average of the trees in it. Now I am sure that a larger area will include a large, possibly equal, number of eucalyptus trees. I have thought about what the average tree would be in that case. Maybe a wattle, no doesn’t fit so I call on you and any others here to enlighten me. Perhaps then I will also know how to average a temperature field.

      • David says:

        My year four primary school teacher used assure me there was “no such thing as a stupid question” so I will do my best.

        1. If you wanted to describe a forest that had equal numbers of pine and eucalypt, I would describe it as, mixed pine-eucalyptus.

        2. To average a temperature field it is the numerator divided by the denominator. So it is the sum of the temperatures divided by the number of temperatures.
        I hope this helps.

        • Mike O'Ceirin says:

          You wrote that forests are an average of the trees in them. To find an average (mean) you need to the sum of a collection of numbers divided by the number of numbers in the collection. This is numbers but you have applied it to trees. Can you explain clearly how you do this if there are different sorts of trees in the forest? Are you asserting that “mixed pine-eucalyptus” is a valid result for a mean?

          • David says:

            “Can you explain clearly how you do this if there are different sorts of trees in the forest?”

            Yes. A large number of naturally growing tropical tress (Black bean, Teak etc.), would constitute a tropical forest. Similarly, if you live in an area, which has a lot of hot and humid weather, then you live in a hot and humid climate.

            “Are you asserting that “mixed pine-eucalyptus” is a valid result for a mean?”


          • BoyfromTottenham says:

            David, I get the distinct impression that Mike O’C is a time waster, or worse a professional timewaster (aka a troller). Or, could he just simply be that stupid? At some point one has to decide it’s better not to encourage this behaviour by responding.

          • Mike O'Ceirin says:

            Since you choose to try the ad hominem path I will write no more after this.

            David wrote “in much the same way that a forests is the average of the tress that
            growth within then. Stromlo forest is a pine forest because it is
            dominate by pine trees” either he is very unclear or proposing an example that is quite ridiculous. Later he accepted the idea that “mixed pine-eucalyptus” is a mean again quite ridiculous.

            If he had asserted Stromlo is a pine forest because the predominate species is pine or that there was a high probability any tree in would be pine he would not have been questioned.

          • David says:

            Just for the record, Mike if you go to my initial
            comment you will see that I used the word average not mean as you implied. I did however, very patiently, explain to you how to take a mean of temperatures.

            So If I make a statement that “the average Australian likes meat pies and Holden cars”, that does not mean that I added up all Chicko rolls, Big Macs and Kababs and divided by the population to get an average of Meat pies.

    • Don Aitkin says:

      I wasn’t looking for a causal relationship, nor even for the answer to which came first, chicken or egg. Rather, I wanted to distinguish between them in a helpful way. And local ‘weather’ events on average do seem to constitute our ‘climate’. Yes, of course our climate tells what sort of weather events we are likely to have, but the weather event is the key, and came first. If they come to change, over time, then our climate will change too.

      • David says:

        Yes Don interesting point.
        In some ways you could almost think of the term “climate” as a collective noun. I know this is not grammatically correct but conceptually you could think of a group of “weathers” as a “climate”.

  • Mike O'Ceirin says:

    I would agree entirely with what Christy wrote about climate models except that we must know how climate and weather works to a much greater detail before there is any possibility of an adequate climate model. If such knowledge determines that we are dealing with a chaotic system then it may never be possible. For those who don’t know the use of the word skill is significant. A climate model that is totally useless is said to lack skill, sort of the climatology version of using “quantitative easing” this then obfuscates what is the truth.

    Titley’s deck of cards is as you write not helpful or accurate since we do not know what card will be added. He I think assumes that, say a card for a typhoon of extreme strength will be added for so many ppm of CO2. Further that it would not be possible otherwise. These cards increase with the rise and so increase the probability of being drawn. I have read a good deal about our recorded climate history. Predicting what it may do is probably not possible. Titley’s proposals to counter the drawing of one of his cards is about as good proposing that a massive costly effort should be initiated to detect and eliminate your little green men. Because how do you know they are not actually depositing their carbon dioxide in our atmosphere. After all we don’t know they are not there!

  • Ulric lyons says:

    So if changes in weather types cause changes in climate, the changes in weather types need an external driver, e.g.:

    • Don Aitkin says:

      Yes. We could get a blocking high that lasted and lasted, and provided a record high temperature figure for our city. That would increase the range of possible future temperatures, and widen our ‘climate’. What would have caused the blocking high is another thing, but your point is valid.

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