Comments on: Does this Make Sense?

By: JC

JC — Tue, 19 Jun 2007 23:44:45 +0000

dearieme, they don't eliminate all urban stations - comparisons of urban to adjacent rural trends showed UHI effect was often small and within uncertainty levels. As for the distinction between urban/rural, from what I've read, it's moot. If a station, rural or urban, shows anomalous data, it's dropped.

I'm not informed on the exact qualifications of the folk at GISS or CRU. I find when these debates degenerate into complicated statistical arguments, it's instructive to look at what other sources tell us about temperature trends. Surface temperature analysis by NASS GISS estimates surface temperatures have risen around 0.2Â°C/decade after 1975. Weather balloon measurements have found from 1975 through 2005, the global mean, near-surface air temperature warmed by approximately 0.23Â°C/decade. Satellite measurements of lower atmosphere temperatures shows temperature rises of between 0.16Â°C to 0.24Â°C/decade since 1982.

By: dearieme

dearieme — Tue, 19 Jun 2007 20:39:15 +0000

“The point is NASA GISS ..remove any spurious signals by normalizing urban stations to surrounding rural stations. Any stations with irreconcilable data are dropped.” Hold on, does that last statement mean “Any URBAN stations with irreconcilable data are dropped”? Assuming it does, it’s not obvious how this procedure differs much from simply eliminating all urban stations. I’d also wonder about the extent to which a simple binary divide urban/rural is a good representation of reality. If I grow a good hedge around a previously open field, it might remain rural but be changed substantially in terms of measured temperature. Lastly, a cultural concern. Are the people doing the reconciling skilled in making measurements, or mathematical modellers/statisticians?

By: dearieme

dearieme — Tue, 19 Jun 2007 20:39:13 +0000

By: Anon E. Mouse

Anon E. Mouse — Tue, 19 Jun 2007 20:24:59 +0000

JC,

ah, got it. thx!

By: JC

JC — Tue, 19 Jun 2007 07:15:19 +0000

Anon E Mouse (cute name), there’s no denying urban areas have gotten hotter over time. But the pertinent question in the Urban Heat Island debate is how has urban heat affected measured temperatures and is the global temperature rise over the past 30 years exacerbated by UHI effect. The GISS/NOAA study shows that UHI effect on measured temperatures is generally minimal, sometimes the trend is actually negative because of the location of the weather station within a city.

By: SailorJG

SailorJG — Tue, 19 Jun 2007 04:48:44 +0000

Ultimately the issue is bias in measurements. A basic principle of stats and all measurement science is if you can not conduct a census (measure or count every member of the population) then the sample you take must be selected at random.
Clearly the permanent weather stations are not located in random places. To your point many are biased to measure temperature in cities (or near air conditioners) or other convenient areas.
This is typical of what I call 'beauracratic science; we can not afford to do it correctly so we'll 'adjust' the numbers in the end to make up for our schlocky approach.
To another point, how many of the world's temperature measuring stations are routinely calibrated? I think I know the answer; few if any.
I trust land based temperature measurements about as much as I trust single point sea level measurements.

By: Anon E. Mouse

Anon E. Mouse — Mon, 18 Jun 2007 23:46:24 +0000

Wouldn't your 42% prove Coyotes' point indirectly? In other words, the parks are getting cooler relative to the surrounding city because the surrounding city is warming up.

Xalem
I can't quite buy your implicit positive feedback effect (albedo driven by temperature changes causes more temperature change, downward death spiral). If that mechanism existed, Earth would've already death-spiraled. Because massive events (large meteorite impacts, etc.) have knocked the earth way off of where we are today...and we returned here, the Earth's temperature mechanism *must* be a negative feedback system.

Temperature goes up for whatever reason, something changes to drive it back down. I don't have to know the mechanism to know that it works that way.

If it were a positive feedback system, temperature goes up for whatever reason, (insert favorite mechanism, perhaps glaciers melt, changes albedo, maybe CO2 bubbles out of ocean, whatever--doesn't matter), temperature goes up even more, more mechanism, more temp. increase, etc., and suddenly we're all Venus-like.

That hasn't happened in hundreds of millions of years despite massive events, temperature excursions, etc. Ergo, not a positive feedback system.

By: John Venlet

John Venlet — Mon, 18 Jun 2007 23:17:17 +0000

Was pointed to your post by Richard Nikoley, after I posted on this subject, noting a retired meteorologist’s questioning of station data at my site. Maybe I’ll step up and see if some of the Michigan stations get documented. Thanks.

By: JC

JC — Mon, 18 Jun 2007 23:07:23 +0000

Actually, a study comparing rural to urban weather stations measurements has been done by NASA GISS and NOAA who examined the last century of temperature data across the USA and found any possible urban warming was small and fell within uncertainty ranges. When attempting to correct urban levels to match surrounding rural levels, they found 42% of cities were getting cooler relative to their surroundings as weather stations are often sited in cool islands (eg - a park within the city). The point is NASA GISS are very aware of any possible Urban Heat Island effect and remove any spurious signals by normalizing urban stations to surrounding rural stations. Any stations with irreconcilable data are dropped.

By: dearieme

dearieme — Mon, 18 Jun 2007 21:58:45 +0000

“By the way, these US sites are probably better than what you would find anywhere else in the world.” Why do you think so?