global average temperatures

Wednesday, May 14, 2014

 USHCN, adjustments, averages, getting it right.

There has been quite a kerfuffle about USHCN adjustments. There was a WUWT post on reasons for the spike, a recalc at Steven Goddard’s site, and more here and here. But the basic elementary issue is little understood. You need to be very careful doing arithmetic with averages of data from disparate situations. I’ll show why.

Fox News host: Climate scientists ‘fabricated’ temperature data

An independent group of researchers called Berkeley Earth have the sole goal of working with the raw data and analyzing it for themselves. Zeke Hausfather is a data scientist with the group.

Hausfather told PunditFact that the warning flag raised by The Telegraph article and bloggers amounts to cherry-picking the data. That’s because while some adjustments might make it seem like scientists are artificially raising temperatures, some adjustments at other stations actually would lead you to the opposite conclusion.

“(They) look through all those thousands of stations, find a few that show big adjustments, and tell everyone that they are evidence of fraud,” Hausfather said. “You will rarely see them pick out stations like Reno, Paris, London, Tokyo, or many others where the adjustments dramatically lower the warming trend.”

Hausfather and his colleagues traced how the adjustment methods changed the temperature data differently around the world since 1850. In the graph below, zero is the baseline. Above zero, temperatures have been adjusted upward, below it temperatures have been adjusted downward.

2015-02-12 14_43_59-figure-4-homogenizationdifferences.png (1170×900).png

In the United States, with about 5 percent of Earth’s land area, the official data file raised temperatures compared to the original readings. But the same methods lowered the data records in Africa, and for all land-based readings taken together, the adjustments basically made no change at all (the black line). With ocean temperature trends, the efforts to compensate for the human factor lower the numbers dramatically.

“The net effect of adjustments is to actually reduce the amount of global warming we’ve observed since 1880 by about 20 percent,” Hausfather said. “Folks skeptical of temperature adjustments are welcome not to use them if they’d like, but you end up with more global warming, not less.”


Climate myths: The cooling after 1940 shows CO2 does not cause warming

After rising rapidly during the first part of the 20th century, global average temperatures did cool by about 0.2°C after 1940 and remained low until 1970, after which they began to climb rapidly again.

The mid-century cooling appears to have been largely due to a high concentration of sulphate aerosols in the atmosphere, emitted by industrial activities and volcanic eruptions. Sulphate aerosols have a cooling effect on the climate because they scatter light from the Sun, reflecting its energy back out into space.

July 9, 2013
Nine of the 10 warmest years on record have occurred since 1998. But forget individual years. That data is noisy. A single year can see its temperatures rocket for reasons having little to do with climate change.Look, instead, at decades. There, the data is a little clearer, as the idiosyncrasies of any one year are balanced by its nine compatriots. That’s exactly what the World Meteorological Association did in a recent report. Here’s the graph:

Each one of those bars aggregates 10 years of data. And the trend, particularly in recent years, is clear: The world is getting warmer. “The period 2000-2010 was the warmest decade on record since modern meteorological records began around 1850,” the authors write.

And it’s not abating. NASA says 2012 was the ninth warmest year on record.

About arnulfo

veterano del ciberespacio
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