I have climate grids (based on climate data from 1961-1991) which I have converted from ascii to raster in ArcGis 10.2.2. The temperature is in degrees celsius. I want to alter the temperature values to incorporate future climate changes in the temperature. I want to alter the whole grid by the same number, but the numbers I want to add to the grid are 0.3 or 0.8 etc, therefore reclassify is not possible. I do not have another layer or grid, I just want to add numbers to the current grid values, for example, all grid values + 0.3°C. Would this be possible using the raster calculator and how would I do it?
Use the spatial analysts PLUS tool to add 0.3 or 0.8 to your climate grid. If you read the help file (syntax section) the second grid which you add to your input grid can actually be a constant and not just another grid. So putting 0.3 into that will add 0.3 to all the cells in your input raster.