"It's critically important to compile a big picture," National Climatic Data Center director Tom Karl says. "The signs that we see are of a warming world."
Sullivan says what is noticeable "are remarkable changes in key climate indicators," mentioning dramatic spikes in ocean heat content, a record melt of Arctic sea ice in the summer, and whopping temporary melts of ice in most of Greenland last year. The data also shows a record-high sea level.
The most noticeable and startling changes seen were in the Arctic, says report co-editor Deke Arndt, climate monitoring chief at the data center. Breaking records in the Arctic is so common that it is becoming the new normal, says study co-author Jackie Richter-Menge of the U. S. Army Corps of Engineers' Cold Regions Research and Engineering Laboratory in Hanover, N.H.
Karl says when looked at together, all the indicators show a climate that is changing over the decades. Individually, however, the story isn't as simple.
Karl says surface temperatures haven't risen in the last 10 years, but he notes that is only a blip in time due to natural variability. When looking at more scientifically meaningful time frames of 30 years, 50 years and more than 100 years, temperatures are rising quite a bit, Karl said. Since records have been kept in 1880, all 10 of the warmest years ever have been in the past 15 years, NOAA records show.
Depending on which of four independent analyses are used, 2012 ranked the eighth or ninth warmest year on record, the report says. Last year was warmer than every year in the previous century, except for 1998 when a record El Nino spiked temperatures globally. NOAA ranks 2010 as the warmest year on record.
They don't have to be records every year, Karl says.
Overall the climate indicators "are all singing the same song that we live in a warming world," Arndt says. "Some indicators take a few years off from their increase. The system is telling us in more than one place we're seeing rapid change."
While the report purposely doesn't address why the world is warming, "the causes are primarily greenhouse gases, the burning of fossil fuels," Arndt says.
The study is being published in a special edition of the Bulletin of the American Meteorological Society.
The Climate of 2012 report: http://www.ncdc.noaa.gov/bams-state-of-the-climate/2012.php
Seth Borenstein can be followed at http://twitter.com/borenbears
Copyright 2013 The Associated Press.