Climate expert Richard Allan: "[W]e're not really at the stage of accurately measuring temperature over land from satellites only...[There are] slow natural fluctuations in the ocean ... if you're measuring for a period of ten, 20 or even 30 years, you might just be measuring part of that natural cycle"

How scientists take earth’s temperature: an interview with climate expert Richard Allan | Carbon Brief

"[W]e're not really at the stage of accurately measuring temperature over land from satellites only, we still need to use meteorological instruments. With satellites you're indirectly measuring temperature, so you have to be careful about other factors that can influence what the satellite sees."
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"[There are] slow natural fluctuations in the ocean ... if you're measuring for a period of ten, 20 or even 30 years, you might just be measuring part of that natural cycle. You need to have a longer term perspective so you can put these bumps and troughs in context of longer timescale changes."