New information and remaining uncertainties .
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Since the 2009 National Climate Assessment, there have been substantial advances in our understanding of the U.S. temperature record (Appendix 3: Climate Science, Supplemental Message 7).
A potential uncertainty is the sensitivity of temperature trends to adjustments that account for historical changes in station location, temperature instrumentation, observing practice, and siting conditions. However, quality analyses of these uncertainties have not found any major issues of concern affecting the conclusions made in the key message (Appendix 3: Climate Science,Supplemental Message 7).
While numerous studies verify the efficacy of the adjustments, the information base can be improved in the future through continued refinements to the adjustment approach. Model biases are subject to changes in physical effects on climate; for example, model biases can be affected by snow cover and hence are subject to change as a warming climate changes snow cover.
Sadly there’s no way to know the truth. We do know though that it is a heavily tampered record, and each tampering is an admission they ( USHCN ) discovered they’d been wrong about all previous data set tamperings, and that realization will surely be shown to be true with this latest tampering when it too is fudged.