We estimated the portion of the surface temperature warming trend over US surface stations below 500m that can be attributed to changes in land-use including agriculture and urbanization, by comparing the surface temperature trends with the trends obtained from the NCEP/NCAR Reanalysis, which does not use surface observations and is insensitive to land use changes (Kalnay and Cai, Nature, 423, 528-531). We will discuss these results, the impact of using Historical Climatological Data adjusted for changes in station location and time of the day and further results shedding light on the possible use of reanalysis for climate trends.