The truth is that we are very poorly served by the current observational network, and can not give precise estimates of what the THC «is», particularly not on annual time scales. (realclimate.org)
In the mid 19th century the largest components of the uncertainty at annual time scales are the measurement and sampling uncertainty and the coverage uncertainty because there were few observations made by a small global fleet. (judithcurry.com)
Detrended correlation analysis in the sample period 1958 - 2015 shows the expected logarithmic relationship between atmospheric CO2 concentration and surface temperature at an annual time scale. (papers.ssrn.com)