<P> The period for which reasonably reliable instrumental records of near - surface temperature exist with quasi-global coverage is generally considered to begin around 1850 . Earlier records exist , but with sparser coverage and less standardized instrumentation . </P>
<P> The period for which reasonably reliable instrumental records of near - surface temperature exist with quasi-global coverage is generally considered to begin around 1850 . Earlier records exist , but with sparser coverage and less standardized instrumentation . </P>
when does the reliable instrument record begin for climate variables
when does the reliable instrument record begin for climate variables
around 1850
around 1850