Last year tied with 2010 as the hottest on record, in a new sign of long-term global warming stoked by human activities, British researchers said Monday, backing up American scientists’ findings of record-breaking heat in 2014. The worldwide data, compiled by the Met Office and the University of East Anglia from records stretching back to 1850, showed average surface temperatures last year were 0.56 degree Celsius (1.0 Fahrenheit) above the long-term average of 1961-90. With 2014, all of the 10 warmest years on record have been this century, with the exception of 1998. Given the statistical ranges, the data echoed findings by scientists in the United States. On Jan. 16, NASA and the National Oceanic and Atmospheric Administration said last year was the warmest on record, just ahead of 2010. The British team said the findings showed “several data sets in broad agreement.” Discrepancies occur because different methods are used to determine temperatures in places with few thermometers, such as the Arctic.