The graph depicts global surface temperature through 2014, with the 10 warmest years highlighted in dark red. (Climate.gov) Earth’s average surface temperature was the warmest since record-keeping began in 1880, according to NASA and the National Oceanic and Atmospheric Administration. December also was the warmest month ever recorded, and was among five months that set records, the agencies reported Friday. The combined land and ocean surface temperature was 1.24 degrees above the 20th century average of 57 degrees, according to NOAA. December’s average global temperature was 1.39 degrees above that 20th century average. The four other months that set records were May, June, August and September, NOAA said. October tied for warmest, according to the agency’s report. The data add to a two-decade string of record warmth planetwide. Except for 1998, the 10 warmest years on record have occurred since 2002, according to NOAA. The increase in global average […]