Paths To Knowledge (dot Science)

What is actually real in Objective Reality? How do you know? Now, prove it's real!

Climate verses Weather: Getting Everything Right

Posted by pwl on February 22, 2009

I’ve been chastised a number of times for using terms from “climate” and “weather” interchangeably. People harangue you and insist that these really are two entirely distinct fields and they always make them sound unrelated too. A little research goes a long way to an understanding of this distinction, and towards showing that my understanding and usage were just fine.

I like how NASA sums it up:

“The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere “behaves” over relatively long periods of time.”NASA

David Lindley, in “Calculating the Future” has an interesting observation about the fuzzy blurring of weather and climate:

“The steadily increasing resolution of GCMs is blurring the already fuzzy distinction between weather and climate. …many medium scale phenomena in current GCMs cannot be calculated directly but must be dealt with by ‘parametrization’, meaning that important aspects of small-scale physics are in essence approximated and averaged over grid cells. … In addition to using computing power to calculate on an ever-finer scale, climate researchers can always think of more science to put into their simulations. … Getting everything right is still years away. … ‘The programming model we use [now] is not viable anymore in the next couple of generations of computers,’ says Bader.” – David Lindley, “Calculating the Future”, Communications of the ACM, January 2009, Vol 52, No. 1, (selected quotes not in any particular order).

So one can say “what is the weather like this week” and also say “what is the climate like this week” and mean essentially the same thing. It all depends up the explicit or implicit time horizon that is being discussed.

It seems that as the computer climate models increase their “reality resolution” and “reality breadth” they approach modeling what most people call weather.

Another point of the article touches on the Limits of Computation which equates Climate Models as akin to “soothsaying with high tech entrails” – take it with a pinch of salt to improve the taste. These limits will never go away for “The Map Is Not the Territory” and never will be. That’s for another post though.

Update
To those of you who still cling to the void idea that “weather is not climate” you need to bring yourself into the latest state of the art in climate science and computer science.

The steadily increasing resolution of GCMs is blurring the already fuzzy distinction between weather and climate. Researchers are beginning to calculate models with 50-kilometer resolution over periods of decades, enabling them to see how climate change might affect the frequency and intensity of extreme storms or the statistics of droughts. Such information, rather than the more abstract concept of global average temperature, starkly conveys the tangible consequences of global warming.

– David Lindley, “Calculating the Future”, Communications of the ACM, January 2009, Vol 52, No. 1.

As we see the geographic area, the size of the computational cell, used for climate models and even just tracking current weather is shrinking. Unfortunately the Earth, or maybe that is fortunately the Earth, is not made up of “grid cells” in a regular matrix to make your array math easy. The Earth is comprised of many irregularly shaped “climate volumes” that interact with each other, some more than others. The size of these volumes is different as well. For example, the Big Island of Hawaii is known for it’s many different “climate types” (supposedly a taste of all climates except arctic). One can move from one “climate zone” to another just by crossing the road!!! I know, I’ve been there and done it. Lush jungle on one side of the road, dry hills with desert like conditions on the other. Tropical rain forest in the river valleys not far away. Three distinct climate zones within hundreds of meters of each other!!!

To properly track and model the climate of the Earth the computer programs must use the actual shape of disparate climate zones which is difficult since they are fuzzy and likely change shape with the seasons and under other conditions such as storms. Regardless a fuzzy volume with the resolution at the level of precision needed for each particular physical attribute being tracked/modeled. In other words temperature needs to be tracked at the volume resolution with sufficient detail to eliminate the need for averaging. That provides high resolution with variable volume size and and fuzzy potentially overlapping shape.

Now for time. Along the time axis any time a volume being tracked changes one of it’s parameters that change needs to be tracked on that time scale of precision. In other words if the temperature is being tracked and it changes on a minute by minute basis then track it that way, if it’s changing on an hourly by hourly basis track that. In other words track every change that occurs.

Of course sensor technology and deployment must catch up with the needs of modeling and tracking science. While we won’t ever be perfect we can achieve a lot with today’s technology.

The time scale for climate/weather is what ever it naturally is and is not the arbitrary distinction that we apply when we attempt to call one thing climate and the other thing weather. It’s a fuzzy distinction at best.

One can also speak of the climate last month being warmer than the same month last year. Remember that words are not always their pedantic meaning that overly-pedantic focused people like to make it out as. Words are flexible.

In addition to using computing power to calculate on an ever-finer scale, climate researchers can always think of more science to put into their simulations. Historically, the growth of computational capacity allowed researchers to integrate previously separate models of ocean, atmosphere, sea ice, and land, and that trend continues on a number of fronts. At the moment, for example, atmospheric carbon dioxide concentration is applied to climate models as an external parameter, derived from the work of scientists who add up emissions from tailpipes and smokestacks and, taking into account the natural processes that absorb and release the gas, try to estimate how much CO2 will be in the atmosphere 10, 20, or more years from now. But this approach misses all types of crucial feedbacks. Changing temperatures of the oceans affects how well they hold dissolved CO2, while changes in the world’s vegetation cover, due to a warming climate, influence the amount of carbon that ends up in the atmosphere rather than being taken up by biomass. Climate modelers are beginning to integrate parts of this complex network of feedbacks into GCMs, so that ultimately they will be able to input human CO2 emissions directly into the models, and allow the computer to figure out where it all ends up—and how that disposition changes in a changing climate.”

– David Lindley, “Calculating the Future”, Communications of the ACM, January 2009, Vol 52, No. 1.

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