Reader daveandrews723 got this E-Mail from Reto Ruedy at GISS
It is true that our estimates for the global mean temperature anomalies occasionally change, since we base them on the best currently available data; those do change with time as records from more stations are digitized and made available, as corrections to earlier incorrect reports are obtained, as metadata are used to account for changes in reports that have nothing to do with climate change but were caused by changes in instrumentations, reporting procedure, location of the measuring instrument etc. Finally, those estimates may change slightly as the time series get longer, which allows us to assess better how to combine records from different stations and how to bridge spatial or temporal data gaps. Sometimes those changes result in increasing trends, sometimes trends are decreased. It seems that the sources you consulted cherry-picked the former instances.
A major change that decreased the trend happened when we included ocean temperatures in addition to land based sources only, and a slight decrease was caused when we adjusted the data for urban effects. All other changes had only minor effects on the global means.
Any major changes/adjustments have always been documented on the web and in the scientific literature by the people who made them (mostly NOAA/NCDC) and so did we whenever we adopted those changes, so none of the graphs you refer to is news to us.
Maybe he isn’t aware of what his team is doing to destroy the global temperature record, but his claims don’t hold up to any scrutiny. The animation below shows NASA changes to the global surface temperature record since 1981.
These are land-only temperatures – so the ocean excuse doesn’t work. The past is always getting colder, and the slope is always increasing. The trend from 1890 to 1978 has increased by 40% since Hansen 1981.
2014 version : data.giss.nasa.gov…….graphs_v3/Fig.A.txt
2012 version : web.archive.org………/graphs_v3/Fig.A.txt
2001 version : wayback.archive.org………graphs/FigA.txt
1981 version : web.archive.org……..Challenge_chapter2.pdf
GISS also overwrites their data as they alter it, and they try to block web crawlers to make it difficult to document their tampering.
The next graph shows the total alterations to the NASA global surface temperature record since 1981.
Perhaps he isn’t aware of what his group at GISS is doing to destroy the integrity of the surface temperature record. His comments above would seem to indicate that.