GISS Guessing Arctic Temperatures “Introduces Substantial Errors”
June 7, 2015
By Paul Homewood
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http://data.giss.nasa.gov/cgi-bin/gistemp/nmaps.cgi?sat=4&sst=3&type=trends&mean_gen=0112&year1=1979&year2=2014&base1=1979&base2=1979&radius=1200&pol=rob
As we know, the Arctic is supposed to be one of the fastest warming regions on the planet. According to GISS, above, most of it is between 2 and 4C warmer than it was in 1979.
Annual anomalies appear to have steadily increased since 1979 at a rate of 0.54C/decade.
http://data.giss.nasa.gov/gistemp/tabledata_v3/ZonAnn.Ts+dSST.txt
However, we also know that there are next to no temperature monitoring stations anywhere near the North Pole. To fill these gaps, GISS rely on temperature readings from land stations up to 1200km away.
http://data.giss.nasa.gov/cgi-bin/gistemp/nmaps.cgi?sat=4&sst=3&type=trends&mean_gen=0112&year1=1979&year2=2014&base1=1979&base2=1979&radius=250&pol=reg
The whole process of gap filling is highly controversial, but in the Arctic it carries particular problems, as Judith Curry explains:
I am also unconvinced by NOAA’s gap filling in the Arctic, and in my opinion this introduces substantial error into their analysis. I addressed the issue of gap filling in the Arctic in this recent publication: Curry JA, 2014: Climate science: Uncertain temperature trends. Nature Geoscience, 7, 83-84.
Relevant text:
Gap filling in the Arctic is complicated by the presence of land, open water and temporally varying sea ice extent, because each surface type has a distinctly different amplitude and phasing of the annual cycle of surface temperature. Notably, the surface temperature of sea ice remains flat during the sea ice melt period roughly between June and September, whereas land surface warming peaks around July 1. Hence using land temperatures to infer ocean or sea ice temperatures can incur significant biases.
http://wattsupwiththat.com/2015/06/04/noaancdcs-new-pause-buster-paper-a-laughable-attempt-to-create-warming-by-adjusting-past-data/
Put simply, the presence of sea ice moderates air temperatures above it, thus reducing volatility. This effect can be seen on the DMI reanalysis of temperatures north of 80 degree.
http://ocean.dmi.dk/arctic/meant80n.uk.php
In summer months, temperatures rarely vary much from the mean (1958-2002), and stay only just above zero. This the chart for last year, but most preceding years show similar patterns.
The situation on land is totally different. There, a puff of wind from the south or a bit of sunshine can dramatically increase temperatures. This effect is accentuated by low humidity in the Arctic, where a given increase in heat content will have a much larger effect than at lower latitudes.
Given these facts, there is no justification at all for gap filling from land stations in the Arctic, and it can only lead to substantial errors, as Judith Curry notes.
It is worthwhile, then, comparing the GISS temperature trends with the UAH lower troposphere ones. (UAH start from 60N, rather than 64N, but this should not make any significant difference.)
http://vortex.nsstc.uah.edu/data/msu/v6.0beta/tlt/uahncdc_lt_6.0beta2.txt
We find that the GISS trend of 0.54C per decade has been dramatically reduced to 0.23C. Unfortunately GISS do not publish monthly anomalies for the Arctic, so we cannot see whether the difference is a seasonal one.
However, if we put the two trends together, we find that most of the divergence has occurred since 2004. In comparison with GISS, UAH shows little trend since 2001.
I understand from the Karl press release that he is now working to “correct” Arctic temperatures for his next NCDC update. If he follows the GISS process, it will only lead to more spurious upward adjustments to the global temperature trend.
It is surely time that the climate establishment accepted that they have absolutely no clue what temperatures are in the Arctic, and take these out altogether from their global calculations. This will, of course, reduce global warming trends, and may even result in cooling in the last decade or so.
In any event, any warming in the Arctic means diddly squat in terms of heat content.
Unfortunately, the “melting” Arctic is their poster child. Take that away, and they have little left.
https://notalotofpeopleknowthat.wordpress.com/2015/06/07/giss-guessing-arctic-temperatures-introduces-substantial-errors/ |
