While Alan mulls over big red dots in NOAA’s graph where no data exists, Frank Lanser finds that GISS global temperature trend is warmed up by weighting land data more.
Guest post by Frank Lansner http://hidethedecline.eu/
The simple task of combining Land surface temperature with Sea surface temperatures has become an odd complex algorithm for GISS. It seems that they weight land data more and more during the 20th century leading to extra heat added to the GISS global temperatures.
Thus in 1900-1920 the GISS LST+SST graph is mostly spot on the used SST graph (the HADISST/Reynoldsv2). This means that the GISS global temperature around 1900-1920 appears to weight land data zero %
The land fraction is increasing during the 20th century, especially after 1980:
The real land fraction of the Earth is of course 30%, but around 1980 GISS uses 40%, in 1988 55% – and in 1995 no less than 73%. (The high land % weighting around 1995 leads to a reduction in temperature decline due to Pinatubo volcanic cooling.)
GISS ends up in 2007 using a land weighting of 67%.
In general GISS defends use of larger land fraction due to their 1200km zones around land stations reaching some Ocean areas. But this does obviously not explain a land fraction that appears to go from near zero to around 70% globally during the 20th century.
Besides, the land temperatures for all stations including the coastal stations appear to show significantly different behaviour compared to the SST´s:
(Taken from PART3 of my new article, http://hidethedecline.eu/pages/posts/the-perplexing-temperature-data-published-1974-84-and-recent-temperature-data-180.php)
And therefore, just shifting SST´s out with land temperatures are questionable.
The topic has been discussed somewhat at Joanne Nova’s site:
What is the impact of the still greater land fraction in GISS data? If the 30% land fraction from the real world was used, GISS 2007 would be 0,55K warmer than GISS 1900.
With the still increasing GISS land fraction actually used, we have GISS 2007 0,72K warmer than GISS 1900.
The difference is 0,17K added by not using 30% land constantly. But this calculation could be done in many ways.
We know for a fact that the oceans cover 70% of the planet. So why not use 70% of data from SST?
GISS global Land + SST
GISS land temp
Both HADISST and Reynolds can be seen using: