climPrep <- function(dataset, years, include.psl = F) {
    if (dataset == "AR4gcm" | dataset == "AR5gcm") {
        datID <- "GCM"
        arID <- substr(dataset, 1, 3)
        varid <- c("tas", "pr")
        if (any(years > 2005)) {
            if (arID == "AR4" & (years[1] < 2001 | years[2] > 2100)) 
                stop("Year range for AR4 projected GCMs restricted to 2001:2100")
            if (arID == "AR5" & (years[1] < 2006 | years[2] > 2100)) 
                stop("Year range for AR5 projected GCMs restricted to 2006:2100")
            if (arID == "AR4") 
                scen <- c("sresb1", "sresa1b", "sresa2") else if (arID == "AR5") 
                scen <- c("rcp26", "rcp45", "rcp60", "rcp85")
            varid <- rep(varid, each = length(scen))
            scen <- rep(scen, length(unique(varid)))
            mainDir <- paste("/Data/Base_Data/Climate/World/GCM_raw/IPCC_", 
                arID, "_monthly/projected_tifs/", scen, "/", varid, sep = "")
        } else {
            if (arID == "AR4" & (years[1] < 1901 | years[2] > 2000)) 
                stop("Year range for most AR4 historical GCMs restricted to 1901:2000")
            if (arID == "AR5" & (years[1] < 1860 | years[2] > 2005)) 
                stop("Year range for AR5 historical GCMs restricted to 1860:2005")
            if (include.psl) 
                varid <- c("tas", "pr", "psl")
            scen <- rep("historical", length(varid))
            mainDir <- paste("/Data/Base_Data/Climate/World/GCM_raw/IPCC_", 
                arID, "_monthly/historical_tifs/", varid, sep = "")
        }
        files <- modinfo <- modnames <- list()
        for (i in 1:length(mainDir)) {
            files[[i]] <- list.files(mainDir[i], pattern = ".tif$")
            modinfo[[i]] <- do.call("rbind", strsplit(files[[i]], "_"))[, 1:5]
            modnames[[i]] <- modinfo[[i]][, 3]
        }
    } else if (dataset == "cru322") {
        datID <- "CRU"
        arID <- ""
        if (years[1] < 1901 | years[2] > 2013) 
            stop("Year range for CRU 3.22 restricted to 1901:2013")
        scen <- rep(c("historical"), 2)
        varid <- c("tas", "pr")
        mainDir <- rep(file.path("/Data/Base_Data/Climate/World/CRU_grids/CRU_TS322"), 
            2)
        files <- modnames <- list()
        files[[1]] <- list.files(mainDir[1], pattern = "*.tmp.*.nc$")
        files[[2]] <- list.files(mainDir[1], pattern = "*.pre.*.nc$")
        modinfo <- NULL
        modnames[[2]] <- modnames[[1]] <- "CRU_TS32"
    } else if (dataset == "cru3101") {
        datID <- "CRU"
        arID <- ""
        if (years[1] < 1901 | years[2] > 2009) 
            stop("Year range for CRU 3.1.01 restricted to 1901:2009")
        scen <- "historical"
        varid <- "pr"
        mainDir <- file.path("/Data/Base_Data/Climate/World/CRU_grids/CRU_TS31_01")
        files <- list.files(mainDir, pattern = "*.pre.*.nc$")
        modinfo <- NULL
        modnames <- "CRU_TS31"
    } else if (dataset == "cru31") {
        datID <- "CRU"
        arID <- ""
        if (years[1] < 1901 | years[2] > 2009) 
            stop("Year range for CRU 3.1 restricted to 1901:2009")
        scen <- rep(c("historical"), 2)
        varid <- c("tas", "pr")
        mainDir <- rep(file.path("/Data/Base_Data/Climate/World/CRU_grids/CRU_TS31"), 
            2)
        files <- modnames <- list()
        files[[1]] <- list.files(mainDir[1], pattern = "*.tmp.*.nc$")
        files[[2]] <- list.files(mainDir[2], pattern = "*.pre.*.nc$")
        modinfo <- NULL
        modnames[[2]] <- modnames[[1]] <- "CRU_TS31"
    } else if (dataset == "cru30") {
        datID <- "CRU"
        arID <- ""
        if (years[1] < 1901 | years[2] > 2006) 
            stop("Year range for CRU 3.0 restricted to 1901:2006")
        scen <- rep(c("historical"), 2)
        varid <- c("tas", "pr")
        mainDir <- rep(file.path("/Data/Base_Data/Climate/World/CRU_grids/CRU_TS30"), 
            2)
        files <- modnames <- list()
        files[[1]] <- list.files(mainDir[1], pattern = "*.tmp.*.nc$")
        files[[2]] <- list.files(mainDir[2], pattern = "*.pre.*.nc$")
        modinfo <- NULL
        modnames[[2]] <- modnames[[1]] <- "CRU_TS30"
    } else if (dataset == "ERA40") {
        datID <- "ERA40"
        arID <- ""
        if (years[1] < 1958 | years[2] > 2001) 
            stop("Year range for ERA-40 restricted to 1958:2001")
        if (include.psl) 
            varid <- c("tas", "pr", "psl") else varid <- c("tas", "pr")
        scen <- rep("historical", length(varid))
        mainDir <- rep(paste("/Data/Base_Data/Climate/World/ERA40/historical_tifs", 
            sep = ""), length(varid))
        files <- modnames <- list()
        for (i in 1:length(mainDir)) {
            files[[i]] <- list.files(mainDir[i], pattern = gsub("expression", 
                "", paste(bquote(expression("^", .(varid[i]), ".*.tif$")), collapse = "")))
            modnames[[i]] <- "ERA40"
        }
        modinfo <- NULL
    }
    return(list(datID = datID, arID = arID, scen = scen, varid = varid, mainDir = mainDir, 
        files = files, modinfo = modinfo, modnames = modnames))
}