Whom would you rather believe? The world’s three best-established atmospheric research institutes – or a Berkeley dream team with the current Physics Nobel Prize laureate, backed up by the largest collection of land temperature measurements ever?

So sorry to confuse you – it doesn’t matter; they say exactly the same thing:

NASA GISS, NOAA and the UK Met Office’s Hadley Centre have all previously carried out independent studies, which reached the conclusion world average land temperatures have risen by (close to) 1 degree Celsius over the second half of the 20^th century. [See also their 2010 temperature records.]

Now a new study, this time conducted by a team of University of California Berkeley researchers, has investigated 1.6 billion meteorological records. The data come from 5 times as many stations as in the previous studies. Again, however, researchers find exactly the same quantitative results for global temperature rise.

“Our biggest surprise was that the new results agreed so closely with the warming values published previously by other teams in the U.S. and the U.K.,” says Professor Richard Muller, who led a Berkeley team of climatologists, statisticians and physicists, including Saul Perlmutter, who earlier this month won the 2011 Nobel Prize in Physics.

The researchers have gone to lengths to investigate popular criticism by climate skeptics, who suggest the temperature records of American and British research institutes would be flawed, because of acclaimed poor station quality, data selection bias or the suggested ‘urban heat island effect’ – that cities are generally warmer than countryside and nature – and that through urbanisation more data would be derived from urban areas – and that this would falsely create the impression of a warming temperature trend.

The Berkeley team find none of these arguments hold true in reality – specified as follows in the summary in the university release:

• The urban heat island effect is locally large and real, but does not contribute significantly to the average land temperature rise. That’s because the urban regions of Earth amount to less than 1% of the land area.
• About 1/3 of temperature sites around the world reported global cooling over the past 70 years (including much of the United States and northern Europe). But 2/3 of the sites show warming. Individual temperature histories reported from a single location are frequently noisy and/or unreliable, and it is always necessary to compare and combine many records to understand the true pattern of global warming.
• The large number of sites reporting cooling might help explain some of the skepticism of global warming. Global warming is too slow for humans to feel directly, and if your local weather man tells you that temperatures are the same or cooler than they were a hundred years ago it is easy to believe him. In fact, it is very hard to measure weather consistently over decades and centuries, and the presence of sites reporting cooling is a symptom of the noise and local variations that can creep in. A good determination of the rise in global land temperatures can’t be done with just a few stations: it takes hundreds — or better, thousands — of stations to detect and measure the average warming. Only when many nearby thermometers reproduce the same patterns can we know that the measurements were reliably made.
• Stations ranked as “poor” in a survey by Anthony Watts and his team of the most important temperature recording stations in the U.S., (known as the USHCN — the US Historical Climatology Network), showed the same pattern of global warming as stations ranked “OK.” Absolute temperatures of poor stations may be higher and less accurate, but the overall global warming trend is the same, and the Berkeley Earth analysis concludes that there is not any undue bias from including poor stations in the survey.

The study data have been handed over to an official academic peer-review process after which they will be included in the IPCC AR5 report of 2013. In order to invite public scrutiny the researchers have provided open access to all materials at www.BerkeleyEarth.org

Let’s face it. With that much academic power, such a large database and overlapping results, there simply is no scientific ground to not acknowlegde world average temperatures are going up, so ‘climate change is real.’

And a recent large survey by the European Commission suggests among Europeans that conclusion has landed.

© Rolf Schuttenhelm | www.bitsofscience.org