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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.
By contrast, NASA data shows worldwide temperatures increasing at a record pace - and nearly a full degree warmer than 1880.
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.
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?
One clue we can see is that NASA has been reworking recent
temperatures upwards and older temperatures downwards - which creates a
greater slope and the appearance of warming. Canadian statistician
Steve McIntyre has been tracking the changes closely on his Climate
Audit site, and reports that NASA is Rewriting History, Time and Time
Again. The recent changes can be seen by comparing the NASA 1999 and
2007 US temperature graphs. Below is the 1999 version, and below that
is the reworked 2007 version.
In order to visualize the changes, I overlaid the 2007 version on
top of the 1999 version, above, and a clear pattern emerged. The
pre-1970 temperatures have been nearly uniformly adjusted downwards
(red below green) - and the post 1970 temperatures have been adjusted
upwards (red above green.) Some of the yearly temperatures have been
adjusted by as much as 0.5 degrees. That is a huge total change for a
country the size of the US with thousands of separate temperature
records.
How could it be determined that so many thermometers were wrong by
an average of 0.5 degrees in one particular year several decades ago,
and an accurate retrofit be made? Why is the adjustment 0.5 degrees one
year, and 0.1 degrees the next?
Describing this more succinctly, the 2007 version of the data
appears to have been sheared vertically across 1970 to create the
appearance of a warming trend. We can approximate shear by applying a
small rotation, so I tried “un-rotating” the 2007 graph clockwise
around 1970 until I got a reasonably good visual fit at six degrees.
What could be the motivation for the recent changes?
Further examination of the NASA site might give us a clue as to what is happening.
NASA staff have done some recent bookkeeping and refined the data
from 1930-1999. The issues has been discussed extensively at science
blog Climate Audit. So what is the probability of this effort
consistently increasing recent temperatures and decreasing older
temperatures? From a statistical viewpoint, data recalculation should
cause each year to have a 50/50 probability of going either up or down
- thus the odds of all 70 adjusted years working in concert to increase
the slope of the graph (as seen in the combined version) are an
astronomical 2 raised to the power of 70. That is
one-thousand-billion-billion to one. This isn’t an exact representation
of the odds because for some of the years (less than 15) the revisions
went against the trend - but even a 55/15 split is about as likely as a
room full of chimpanzees eventually typing Hamlet. That would be
equivalent to flipping a penny 70 times and having it come up heads 55
times. It will never happen - one trillion to one odds (2 raised to the
power 40.)
Particularly troubling are the years from 1986-1998. In the 2007
version of the graph, the 1986 data was adjusted upwards by 0.4 degrees
relative to the 1999 graph. In fact, every year except one from
1986-1998 was adjusted upwards, by an average of 0.2 degrees. If
someone wanted to present a case for a lot of recent warming, adjusting
data upwards would be an excellent way to do it.
Looking at the NASA website, we can see that the person in charge of
the temperature data is the eminent Dr. James Hansen - Al Gore’s
science advisor and the world’s leading long-term advocate of global
warming. Source
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