Open Mind

There are many studies of the changes over time of the average temperature throughout the year, for individual locations, regions, continents, oceans, and the globe. There’s a fair amount of attention paid to the difference in warming between winter and summer seaons. These phenomena are two aspects of the annual cycle of temperature in most locations. The zero point is the average throughout the year, and the amplitude is the size of the contrast between winter and summer (roughly speaking). But one aspect of the annual cycle of temperature that’s usually neglected is the phase of the cycle, i.e., the moment at which annual temperatures reach their summertime peak and wintertime trough.

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A reader recently suggested that daily or even hourly temperature measurements were more relevant to the human experience of global warming, than monthly or annual averages. I’m not sure whether I agree or not. Daily values, especially extreme ones, are the most visible and unavoidable aspect of weather, but monthly, annual, or even decadal averages of climate parameters can, in some cases, be more relevant.

A hot day isn’t likely to cause massive melting of glaciers or ice sheets, while an entire hot season, year, or decade is. A severe chilling frost may not be sufficient to check the survival of pine bark beetles and thereby protect pine forests from those parasites when a cold season may be more than sufficient. Precipitation is a case where longer-term averages seem to dominate the human impact of the weather. A day without rain is a normal event, but a year without rain is a disaster for human societies; likewise, a day of heavy rain may bring problems, but a week of heavy rain is likely to lead to the kind of flooding that can disrupt the conduct of life.

But it can’t be denied that individual days (or even hours!) can also have a notable impact. If the rain is heavy enough, then a single day can lead to flooding. And if the temperature, even for a day, is hot enough or cold enough, it can not only disrupt society, it can threaten human health.

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The longest single instrumental temperature record, one which has recently come under scrutiny in comments on this blog, is the Central England Temperature, or CET. The primary CET record consists of estimates of monthly average temperature from 1659 to the present. Let’s take a close look.

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As you’ve probably noticed, I haven’t updated or commented much this week. Work is keeping me intensely busy, and will for the remainder of the week. I expect to return to “normal” blog operations Sunday or Monday.

I’m also not able to moderate comments except for limited hours during the day.

But I appreciate continued readership and commentary. Keep ‘em comin’, maintain patience, we’ll be back to our usual rapid-fire within just a few days.

The latest issue of Scientific American has an interesting article on the use of the internet for scientific research. The web is revolutionizing the way a lot of scientists do things by making it easier to communicate, access resources, acquire data online, and collaborate in ever larger and more productive ways. It’s also changing the fundamental way in which scientists communicate with the public, in some cases making the very thought processes behind scientific research accessible to a wide audience.

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A reader calling himself “Raven” recently linked to this page by Hans Erren which graphs some central European temperature records going back to the 1700s. It features this graph:

This shows annual average temperature for five central European cities. The data are stated to be from GISS, but since the GISS website no longer provides data prior to 1880 the author links to the GHCN version 1 where the early data are still available.

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If you testify in a court of law in the United States, you have to swear an oath to be honest. This oath requires you to tell the truth, the whole truth, and nothing but the truth. If you violate this oath in sworn testimony, you’re guilty of the crime of perjury: deliberately giving false or misleading testimony under oath.

Noel Sheppard, in his latest entry on the “Newsbusters” site, reproduces a graph prepared by Joe D’Aleo, whose work we have already examined. If Sheppard’s post or D’Aleo’s graph were sworn testimony in a court of law, I’d charge them with perjury.

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One of my specialties is period analysis, identifying and quantifying periodic and pseudo-periodic fluctuations in time series. The essence of periodic fluctuations is that they repeat. It’s not just that the signal forever goes up and down, possibly in random fashion; there’s a pattern to the ups and downs, and that pattern repeats in cycles — not necessarily perfectly (in the case of pseudoperiodicity), not even necessarily forever, but repeats often enough and regularly enough that we can, at least in the short term, have some idea of what the next cycle will look like, given that we know the most recent cycles.

This may end up being one of my more controversial posts, because I’m going to expound on one of my “pet peeves” in science: the claim of periodic or pseudoperiodic behavior when none exists. It might just be the most common mistake made by working scientists, and it makes its way into the peer-reviewed literature all the time. It just goes to show that peer review is a necessary, but hardly a sufficient, condition for correct results.

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I notice that folks are discussing things which are only slightly related to the thread, or not related at all, probably because there’s no open thread appropriate for such discussion. So here’s an open thread.

No Britney, no Master’s tournament, no more Bach-vs-Mozart wars, and let’s NOT discuss the hockey stick. That’s not off limits permanently — but after literally weeks of back-and-forth on that topic on many threads, this blog is taking a week off hockey.

Total snow cover for the northern hemisphere (NH) is an important indicator of the condition of the climate, and a factor affecting northern-hemisphere albedo. More snow cover doesn’t necessarily indicate colder temperatures. Total snowfall depends on temperature and humidity, and warmer temperatures increase the amount of water vapor the air can hold, increasing the total potential snowfall. Still, they’re at least partly related to temperature; there’s certainly more snow during winter than summer. Snow is an important part of the earth’s albedo, or reflectivity to incoming sunlight; fresh snow is one of the most highly reflective surfaces found on the planet.

Has snow cover shown trends over the last several decades? NH snow cover data since late 1966 can be obtained from Rutgers University. Let’s take a look.

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