Thomas R. Karl

Global warming hiatus debate

Karl was the lead on a study on the question of the possible existence of a hiatus in global warming, as discussed in the IPCC Fifth Assessment Report . In the study, published in the American Association for the Advancement of Science (AAAS) Science journal in June 2015 and based on previously published datasets, they found no indication of a slowdown, even in the period from 1998 to 2012 which had been highlighted by the IPCC. This analysis incorporated the latest homogenization corrections for known biases in ocean temperature measurements as published by others in NOAA's Extended Reconstructed Sea Surface Temperature dataset version 4, and land temperatures from the new International Surface Temperature Initiative dataset, integrated with NOAA's Global Historical Climatology Network. Scientists working on other datasets welcomed this study, though the view was expressed at the time that the short term warming trend had been slower than in previous periods of the same length. After he published these results, Karl was attacked by climate change denialists, including Lamar Smith, chair of the House Science Committee. In 2017 the findings of the Karl et al. study were confirmed by another group of scientists using different methodologies.