A tale of two thermometers

A paper published in scientific journal Nature this week has reignited the debate about Global Warming, by predicting that the earth won't be getting any warmer until 2015. Researchers at the Leibniz Institute of Marine Sciences have factored in cyclical oceanic into their climate model, and produced a different forecast to the "consensus" models which don't.

But how will we know whether the earth is warming or cooling? Today, it all depends on the data source.

Two authorities provide us with analysis of long-term surface temperature trends. Both agree on the global temperature trend until 1998, at which time a sharp divergence occurred. The UK Meteorological Office's Hadley Center for Climate Studies Had-Crut data shows worldwide temperatures declining since 1998. According to Hadley's data, the earth is not much warmer now than it was than it was in 1878 or 1941.

Hadley's data (April 13, 2008)

By contrast, NASA data shows worldwide temperatures increasing at a record pace - and nearly a full degree warmer than 1880.

NASA's data (April 13, 2008)

The other two widely used global temperature data sources are from earth-orbiting satellites UAH (University of Alabama at Huntsville) and RSS (Remote Sensing Systems.) Both show decreasing temperatures over the last decade, with present temperatures barely above the 30 year average.

Anomalies 1998-2008; University of Alabama (UAH)

Anomalies 1998-2008; Remote Sensing Systems (RSS)

Confusing? How can scientists who report measurements of the earth's temperature within one one-hundredth of a degree be unable to concur if the temperature is going up or down over a ten year period? Something appears to be inconsistent with the NASA data - but what is it?