Skip to comments.Hot or Not?
Posted on 01/04/2003 1:46:08 AM PST by JohnHuang2
Was 2002 one of the hottest years in history? After all, pronouncements of record warmth for 2002 were made since the beginning of 2002.
For example, in February 2002, NOAA warned that "November 2001-January 2002: Warmest on the record in the US; Global temperatures warmest on record [in the 123 years of record keeping] in January." And last April, the BBC news claimed that January, February and March of 2002 "were globally the warmest" since records began in 1860. By August 2002, CNN.com announced that "Globally 2002 is likely to be warmer than 2001, and may even break the record set in 1998."
By December 11, 2002, another news blizzard dumped stories feeding off a press release from the Earth Policy Institute's Lester Brown, with headlines like "2002 heading for No. 2 spot in climate records"; "Scientists: '02 second hottest as warming speeds"; and "Scientists: Humans the main culprit in global warming."
And if the newspapers are to be believed, the new year is already gearing up to be a hot one. The New York Times writer Andrew Revkin announced on New Year's eve that "Climate experts say global temperatures in 2003 could match or beat the modern record set in 1998 ...".
All of this sounds like bad news. But how alarmed should we be?
'Truly Meaningful? to Nobody'
First of all, it's important to remember that the attempt to determine the relative ranking of a measured global surface temperature, given current limitations, is impossible. To understand why this is so, let's examine how global surface temperature is derived.
The premise is simple: Start with measurements taken from thermometer stations scattered across the globe. Now average all the good measurements within, say, a 5 degree by 5 degree box (that makes a total of 2592 boxes to cover the earth). From that, form a global mean from the values in all the 2592 grid boxes.
Sounds simple enough. The only problem is temperature has not been reliably measured in all grid boxes over time. Far from it. For example, the number of grid boxes covered by thermometers has increased by more than a factor of five since the onset of the instrumental record in the 1860s.
Moreover, local and regional temperatures are temperature readings made in absolute terms, e.g., 48 F. Those local absolute temperatures must be accurate in order to avoid systematic errors when the global average is computed.
For those reasons, the NASA Goddard Institute for Space Studies web page says that the "reported temperature [by the local news media] is truly meaningful only to a person who happens to visit the weather station at the precise moment when the reported temperature is measured, in other words, to nobody."
NASA's web page then points out that "regional absolute temperature ... cannot be determined from observations alone" because of important measurement difficulties. These difficulties arise from the lack of homogeneous sampling of areas with differing geographical features (e.g., land or ocean, changing surface vegetation or altitude of the weather station) over time or a consistent time of observation (e.g., local noon versus midnight, winter versus summer).
Chasing after the absolute global surface air temperature is an enormous task. It is a task that cannot be done on the basis of averages of thermometer readings alone, but must solicit help from the output from complex computer simulations of climate. How reliable is such a model-driven process of averaging thermometer readings? The NASA web page says that "the most trusted [climate] models produce a value of roughly 14 Celsius, i.e., 57.2 F, [for the global mean temperature] but it may easily be anywhere between 56 and 58 F; and regionally, let alone locally [like those given by your nightly local weather report], the situation is even worse." In short, the global average is uncertain by about 2 F - that's an uncertainty twice as great as the 1 F surface global warming claimed for the entire 20th century!
Looking at Figure 1 below helps us better understand some of the uncertainties in the global average temperature. The top panel is the "global" surface temperature data from the United Kingdom Meteorological Office/University of East Anglia's web page. Taken at face value, the figure indicates that the global temperature was exceptionally high in the 1990s, with 1998 being the warmest and 2002 the second warmest.
"In 10 out of 16 simulations, the estimate of the warmest year in the last century based on the masked model output agrees with the true answer obtained from the globally complete model data. However, estimates of the 3 (5) warmest years (including their relative ranking) in the masked and globally complete model output agree in only 3 (2) of 16 simulations. In two cases, the year that is the warmest based on globally complete model output is not among the three warmest when estimates are made from masked model output. Thus, even though the warmest years occurred during the last 1-2 decades, when observational coverage was relatively good, estimates of the relative ranking of the warmest years are still sensitive to sampling errors induced by incomplete and time-varying coverage of observational data." (Emphasis added)
|Updated: 7:00 AM EST on January 04, 2003
Observed at Bangor, Maine
|Temperature||23 °F / -5 °C|
|Windchill||10 °F / -12 °C|
|Dew Point||19 °F / -7 °C|
|Wind||NNE at 16 mph / 25.7 km/h|
|Wind Gust||25 mph / 41 km/h|
|Pressure||29.87 in / 1011 hPa (Steady)|
|Visibility||1 miles / 2 kilometers|
|Clouds||Overcast (OVC) : 900 ft / 276 m
|Max Temperature||Normal: 28°F Record: 57°F (1950)|
|Min Temperature||Normal: 9°F Record: -23°F (1981)|
|Yesterday's Maximum||27 °F / -3 °C approx.|
|Yesterday's Minimum||12 °F / -11 °C approx.|
|Yesterday's Heating Degree Days||46 approx.|
JH2, note that the record warm day for the date is in 1950 and the record cold is from 1981.
I see this almost everyday when checking the weather.
By the way, we're supposed to get 12" to 18" of white stuff today.
Batten down the hatches!
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