Are all anomalies created equal?

Climate is changing; climate has always changed. It is a chaotic system where local microclimate effects can be strong. How can any global average be sure to represent adequately the local nuances and variations (anomalies)? In the existing input data, the spatial and temporal coverage is highly variable. What spatial resolution is needed to capture local responses to changes in long-term weather patterns? How can one station, say in the lee of mountains and in an arid rain shadow, area adequately represent an entire region, when another 1-200km away with completely different altitude, cloud cover, rain/humidity and temperature responds differently but is only present in the record for a fraction of the time of the arid one?

Using anomalies is necessary yes, but how can you be sure the response of these two stations will track each other over long periods? The program requires an overlap of only 20 years minimum when they both report. What GIStemp does is assume that one station will always be a good proxy for others in the area.

If climatic systems are cyclical (whether regular or not), modelling in engineering systems aspires to at least 3 full cycles to show stability of the relationship between two datasets. We just don’t have that quantity of data.

Temperature anomalies for stations in Madagascar

Other examples: the Arctic; China; Turkey. You might say these are cherrypicks, but ask yourself this – if a cycle shows up in one station but an adjacent one has continuous warming, which one is right? Is this not a case of the differences I suggest above? In this case should we not be concerned if one or other of them drops out of the data record used by GIStemp?

This was a response to a blog comment (thread here) about GIStemp and the calculation of global average temperatures, er, anomalies. Stopping by at E.M.Smith’s blog this evening I found he had just posted a link and discussion of agricultural degree days which kind of supported the point I was making. By overlaying climate stations on a degree day map, we can look at the spatial resolution of data reporting with respect to temperature variations within the landscape. Does this look like adequate coverage?

Degree days map for Washington with overlay of stations (diamonds) reporting climate data into GIStemp

In the USA I would expect coverage to be adequate (although I will probably follow up and look at temporal coverage also – the ‘Station Drop-out’ issue).  For other parts of the world not so.

As anna v commented yesterday evening on WUWT:

“… a 1C anomaly in a region that has an average temperature of 273K has a completely different physical manifestation than a 1C anomaly where the average temperature is 288K.”

So the question is – are all anomalies created equal?

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5 Responses to Are all anomalies created equal?

  1. Doug Proctor says:

    What the anomalies are is critical to what they mean. By themselves, anomalies are just data, without significance. Context gives them meaning, and then we have “information”. We are inundated with data, but sparse on information.

    Global temperature anomalies or rise: 0.7*C is of no importance if it is held within a daily variation of >12C* in summer, and 20C* in winter, and a summer to winter variation of >40C*, as it is in Calgary (with max to min differences of >60C*!). Somehow, for it to be significant, the 0.7 must be concentrated. Is it at night, during the day, during the winter, or the summer? At the same time, if CO2 is to blame, it must be global, so it can’t be concentrated in one part of the world. So where is the temperature concentration that has impact on the planet and our lives? I see 5C* in the Arctic, but not the Antarctic, but just during the summer. I can’t identify where the significant concentration exists, if it is not just an artefact of temperature rise bubbles that move around the world month to month, year to year.

    I first started investigating the AGW claim with studies about mechanisms. Now I’m back at the start: what does the global rise of 0.7*C mean at a physical level to the specific biosphere?

    Where is the disaster-in-the-making happening? We hear about the disaster in front of us every day in every way, but I can’t find it in the temperature data. What am I missing? I ask my AGW friends, and they get twitchy, falling back on ideology: we need to consume less and be kinder to the planet. I agree. Who wouldn’t? But where is the current temperature “rise” long-term and concentrated?

  2. Verity Jones says:

    Doug, I agree with your questions (very similar to my own train of thought). Thanks for sharing them. I deliberately didn’t follow through on this post as I hope it gets people thinking. I have been working through some of the ideas, although I’ve been a bit short on time since posting this.

  3. E.M.Smith says:

    I would also point out that the stations on that Washington map don’t all exist at the same time. In California, GHCN has only 4 stations in 2009. All near the ocean and population centers. I would expect to see something similar in Washington. So two maps of Washington, one of them for just 2009-10, would likely show a strong sampling bias in the “now” data vs the “then” data.

    Any chance you could post such a map? A companion to the above, but showing only where they measure now for GHCN?

  4. Pingback: The trouble with anomalies… Part 1 | Digging in the Clay

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