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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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The Consensus Project

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	Climate's changed before
	It's the sun
	It's not bad
	There is no consensus
	It's cooling
	Models are unreliable
	Temp record is unreliable
	Animals and plants can adapt
	It hasn't warmed since 1998
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Archived Rebuttal

This is the archived Intermediate rebuttal to the climate myth "Temp record is unreliable". Click here to view the latest rebuttal.

What the science says...

Numerous studies into the effect of urban heat island effect and microsite influences find they have negligible effect on long-term trends, particularly when averaged over large regions.

The goal of improving temperature data is something we can all agree on and on this point, the efforts of Anthony Watts and Steve McIntyre are laudable. However, their presupposition that improving temperature records will remove or significantly lower the global warming trend is erroneous.

Adjusting for urban heat island effect

When compiling temperature records, NASA's GISS goes to great pains to remove any possible influence from urban heat island effect. They compare urban long-term trends to nearby rural trends. They then adjust the urban trend so it matches the rural trend. The process is described in detail on the NASA website (Hansen 2001).

They found in most cases, urban warming was small and fell within uncertainty ranges. Surprisingly, 42% of city trends are cooler relative to their country surroundings as weather stations are often sited in cool islands (a park within the city). The point is they're aware of UHI and rigorously adjust for it when analyzing temperature records. More on urban heat island...

Climate Audit and NASA's "Y2K" glitch

Steve McIntyre's discovery of a glitch in the GISS temperature data is an impressive achievement. Make no mistake, it's an embarrassing error on the part of NASA. But what is the significance?

Figure 1 compares the global temperature trend from before and after adjustments. Before the error was discovered, the trend was 0.185°C/decade. After corrections were made, the trend was still 0.185°C/decade. The change to the global mean was less than one thousandth of a degree. More on NASA's Y2K glitch...

GISS temperature before and after Y2K adjustment
Figure 1: Global temperature anomaly before (red squares) and after (black diamonds) NASA's "Y2K" corrections (Open Mind).

Other lines of evidence for rising temperatures

The surface temperature trends are also confirmed from multiple, independent sources:

Surface temperature analysis by NASA GISS finds strong agreement with two independent analyses by CRU's Global Temperature Record and NCDC.
Weather balloon measurements have found from 1975 through 2005, the global mean, near-surface air temperature warmed by approximately 0.23°C/decade.
Satellite measurements of lower atmosphere temperatures show temperature rises between 0.16°C and 0.24°C/decade since 1982.
Ice core reconstructions found the 20th century to be the warmest of the past five centuries, confirming the results of earlier proxy reconstructions.
Sea surface temperatures, borehole reconstructions and ocean temperatures all show long-term warming trends.

Updated on 2010-06-26 by John Cook.

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