PROBLEMS WITH SURFACE TEMPERATURES-Dr V Gray

Here.

Excerpt:

It is quite impossible to obtain a statistically or scientifically acceptable estimate of mean global temperature or its variability over time, from readings on the earth’s surface, for the following reasons:

• Random distribution of measuring equipment is impossible, and thus, so is a truly global average of known accuracy.

• Continuous temperature measurement in any one location has only been possible recently. For a longer record “Mean Daily Temperature”, must be used. This consists of the mean of the maximum and minimum temperature over a variable 24 hour period, which does not even usually refer to a standard day. Such a measurement gives only a biased average, of unknown accuracy, even at a single site.

• There is no quality control system for weather station and ship-based measurements. Few aspects of the process are standardized, even within a single country. Differences and changes in instruments, shelter, location, distance from buildings and vegetation are seldom studies or allowed for. Personnel are often voluntary (as in the USA), poorly paid or unpaid (even as prisoners), and of variable qualifications or training. The administration can change frequently and even change nationality. Visits to sites may be infrequent, and impractical by those processing international data. Some instruments are on top of buildings, within a few meters of them, or situated on asphalt or concrete or occasional snow. A recent study in the United States has shown that even the “approved” sites in that country are non standard -- if judged by World Meteorological Office recommendations [Dave and Pielke Sr 2005].

• Measurement sites suffer from discontinuity of location and variability in numbers and thus in the extent of global coverage (100 weather stations in 1850, 8000 in 1980, 3000 today), as well as gaps in records.

• Attempts to correct for some of these sources of error are largely confined to the continental USA. In most countries there are too few sites for comparison purposes, and methods developed in one country may not be valid elsewhere.

• The oceans constitute 71% of the earth’s surface but temperature measurements at sea have even greater potential errors than measurements on land.

• Weather data are considered commercial and are often not generally available to the public without a fee. The details of processing of the data are not made available to independent observers or “peer reviewers.”

A whole host of additional difficulties have been identified by Gray (2000) and have been expanded in recent papers by Pielke Sr et al [2007], Runnalls and Oke [2006], Pielke et al [2007b], and D’Aleo et al. [2007]. They include the high and variable thermal gradient at the surface, the effects of discontinuities in number and location of sites, instrument calibration and change, land-use changes, water vapour effects, political changes, wars, gaps in the data….

A set of measurements widely regarded by the IPCC to show that urban effects are negligible [Jones et al 1990] gave the opposite results with a selection of the same data in a paper that included two of the same authors, in the same year [Wang et al 1990].

Another paper, also much quoted as proof that urbanization effects are negligible, even includes the words “No Difference Found” [Peterson 2003]. The actual paper,however, found a difference of 0.31ºC between the urban and rural sites. But so many errors and “corrections” were necessary that when these were made the urban/rural difference could no longer be “found."