The National Climate Data Center at NOAA has just released its statement on the global temperature of 2013 and concludes that last year was the 4th hottest on record going back to at least 18801, essentially tying with 2003. Globally, 2013 was hotter than 2012, and was 0.62 degrees C warmer than the 20th century average (or, the anomaly over the 1901-2000 period.)
Data from NASA's Goddard Institute for Space Studies and the Met Office Hadley Centre (known for HadCRUT4) have yet to weigh in on their findings for December, and therefore the year, but the results can be expected to be virtually the same.
Below is a chart showing a projection of NASA's global temperature records since 1880, with the December 2012-November 2013 period suggesting 2013's standing.2
Whereas the United States experienced it hottest year ever in 2012, Australia had its own hottest year ever in 2013: the year of the "angry summer." In China, the soggy July and August heat led to new all-time record highs in Shanghai and Hangzhou, and the compound of air temperatures above 105 F with high dew points flirted with the wet bulb temperature—that which is the maximum temperature humans can still cool by sweating—while deadly smog alloyed with winter which produced another environmental disaster of its own. Floods in Alberta, central Europe, the Amur River of east Siberia, Pakistan/Afghanistan, and Colorado were unspeakable in their brute. California endured its driest year, with wildfires lapping the shores of Yosemite National Park. Oceanic heating spiked to record highs. Sea surface temperatures in the northern Pacific were sharply above average, and contributed to typhoon Haiyan's cataclysmic sustained winds of 190-195 mph at landfall with the Philippines. Sea levels continued to rise. Arctic sea ice improved from deep record lows set in 2012, but extent and volume remained dangerously below average.
By leaps and bounds, 2013 was a very active year for extremes, which says something after coming from the extremes endured in 2011 and 2012. This was so, despite the lack of a clear signal from the year-to-year climate patterns often dictated by the El Niño-Southern Oscillation (ENSO). A weak El Niño was expected for late 2012/early 2013, before cool water short circuited the momentum, sending the remainder of 2013 into a neutral state, making it more prone to regional climate patterns such as the North Atlantic Oscillation (NAO), Arctic Oscillation (AO), Indian Ocean Dipole (IOD), and so forth. By some accounts, this made 2013 the warmest neutral year on record.
While the temperature "rankings" are of a fleeting moment, soon to be obsolete, the 134-year record does make some clear statements: 2013 was one of the hottest years in the Holocene epoch, global warming since the early 1900's is continuing, it validates over a century-and-a-half of meteorological physics3, and there is nothing which fundamentally changes the expectations for years ahead. Basic physics says that the chart above can be expected to zoom out of sight decades from now. The clear peak for now, 2010, will be at the foot of intense warming in due time. As another interesting consequence of last year, 1988 is no longer in the top twenty warmest years. You may recall the history of global warming's prominent rise to publicity, when NASA scientist James Hansen gave Senate testimony in June of 1988, reporting that the first five months of 1988 were much warmer than average, that 1988 would very likely finish as the hottest year on record, and that this could not be explained by natural variation alone.
“It’s time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here.” ~James Hansen; June 23, 1988That 1988 has dropped from the list of twenty hottest years for global temperatures is beyond its symbolic importance. It's a forlorn reminder of urgency being supplanted by complacency, and the sort of wait-and-see abeyance to action with which humans disadvantage themselves in the long term. Wait-and-see has made its case, and the build-up of carbon dioxide, nitrous oxide, methane, CFC, HFC, and now PFTBA concentrations in the atmosphere are becoming the dominant forces of our warming trend. Wait-and-see is not sound wisdom. This is unassailable. Laws of physics certainly do not suspend for us.
Since 1988, the sordid "hottest year" title has been replaced multiple times. Since James Hansen's testimony, 1990, 1995, 1997, 1998, 2002, 2005, and 2010 have all shared this fleeting moment. They are among the data points that constitute the trend which reflect geological history in its making. In fact, 2013 did not need to have its moment at number one for us to see this. It fits squarely within a trend that is consistent with the warnings of a world 2-4 degrees C (or roughly 4-7 degrees F) warmer than present by century's end. And it's also becoming apparent that there's no particularly "safe" limit for dramatic global temperature rises. A 2 degree C rise by 2100, a "target" that was established in the 2009 Copenhagen Accord, would be disastrous.
Models from NOAA's Climate Forecast System (CFS) have indicated that El Niño may return with ferocity beginning this summer, with above-average equatorial Pacific temperatures. In oceanic physics, should a self-sustaining positive feedback of deepening warm water volumes (extending from the deep western Pacific towards the shallower east), leading to weaker trade winds, leading to more oceanic warming, a successful El Niño ensues; and then the transfer of oceanic heat to the atmosphere through convection will result in some very dramatic temperature anomalies on land. Simply, 2014 may very well be the warmest year of the Holocene, and 2015 possibly more-so. We can forget any bluster about there being a "pause" or that there's a global cooling taking place. Science does not beckon your opinion on whether you "think" or "believe" global warming is happening. Science requires evidence. And for the case of global warming, last year provided a preponderance of such evidence; evidence which has not just emerged from the ether, but has been an ongoing process for decades. A fleeting moment, indeed a blink in geological history.
1. NCEP/NCAR—which reanalyzes weather stations to fill voids in the global coverage using satellite data and laws of physics—is even more aggressive, suggesting 2013 was the 3rd hottest year since 1948, behind 2010 and 2005. The Japan Meteorological Agency reports that 2013 was the 2nd hottest year on its record since 1891. Satellite data collected by the University of Alabama-Huntsville (UAH) indicates that 2013 lower troposphere temperatures were the fourth hottest going back to 1978. Differences between indices arise from varying coverage areas, atmospheric levels, and interpolating missing grid data.
2. NASA's global temperature index (Land-Ocean Temperature Index, or L-OTI) has very high global coverage, which it achieves by blending or smoothing local station data (such as those which are sparsely placed in the Arctic) for up to 1,200 km. This provides a sensible measure of changes in the Arctic and Antarctic.
3. Humans' understanding of the physics and chemistry behind global warming continues to advance, having discovered nary a hitch in their general theory. Global warming theory asserts that there is an average (thus, overall) increase in the heating of the Earth's atmosphere and oceans as it tries to reach an equilibrium state in response to the extra energy that results from the increasing concentration of greenhouse gases in the atmosphere. More and more studies are released, and they more and more affirm humans' role in this trend. This journey to self-awareness began nearly two centuries ago—before satellites, the IPCC, or computer models could chart the course—beginning with the physics of the greenhouse effect that was posited by Joseph Fourier in the 1820s, and decades later when John Tyndall discovered that water vapor and carbon dioxide were very effective at blocking outgoing longwave radiation (OLR) that would otherwise escape into space. Thus, the heat from the sun's radiation is trapped. This was understood to have had some role in the suspected receding of the glaciers that once coated northern Europe. It also differentiated why Earth was a habitable planet, and Mercury, Venus, and Mars not. Fourier and Tyndall established the crucial foundation for global warming theory, and carbon dioxide's warming effect would be understood to be so, regardless that it came from outgassing from the oceans in pre-historic eras, volcanoes, or the burning of fossil fuels. As a witty science journalist by the name of Peter Hadfield laid plainly, "It's the same stuff!"
Swedish physicist Svante Arrhenius appears to be the first scientist who questioned what effect a doubling of the atmospheric concentration of carbon dioxide would have on the Earth's temperature, supposing fossil fuels were a key source of carbon dioxide and would continue to be burned in the future. In an 1896 publication in the Journal of Science, titled "On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground", he concluded that it would warm 5 to 6 degrees C on average. It's a paper that is publicly available to this day. Works from Guy Stewart Callendar in the 1930s unequivocally pointed to the burning of fossil fuels as a key source of carbon dioxide to explain rising temperatures; while in 1931, E.O. Hulburt posited the potential of water vapor as a positive feedback to enhance the warming effect of carbon dioxide. Refinement over the decades since through the works of Gilbert Plass, Bert Bolin, Hans Suess, L.D. Kaplan, Steve Schneider, Kevin Trenburth, Michael Mann, and the hundreds of other climate researchers in this day have done us an invaluable favor.