2014: Hottest Year in Recorded Human History

Earth had its warmest year on record in 2014, said NOAA and NASA at a joint press conference today. According to NOAA's National Climatic Data Center, global surface temperatures in 2014 were 1.24°F (0.69°C) above the 20th century average, highest among all years in the 1880-2014 record, easily breaking the previous records of 2005 and 2010 by 0.07°F (0.04°C). Using independent measurement techniques but mostly the same set of surface stations, NASA also rated 2014 as the warmest year on record, as did the Japan Meteorological Agency (JMA). The other widely-cited global temperature measurement, from the UK Met Office, has not yet been released for 2014. Because there are variations in how each group handles the Arctic and other data-sparse areas, there are slight differences in the "top ten" lists of warmest years produced by each group. However, 2014 is the first year since 2005 that has topped the temperature charts for both NASA and NOAA.


Figure 1. Earth's departure in temperature from the 20th century average during the period 1880 - 2014, according to NOAA.

Including 2014, nine out of ten of the warmest years in the 135-year period of record have occurred during the 21st century (2001–2014), with 1998 (4th warmest year on record) rounding out the top ten. Global land temperatures were the 4th warmest on record during 2014, and ocean temperatures were the warmest on record. Global satellite-measured temperatures in the lower atmosphere were the 3rd or 6th warmest in the 36-year record, according to UAH and RSS, respectively. The year 2014 joined 2012 and 2013 as having near-average precipitation on balance across the globe.


Figure 2. Departure of global temperature from average for 2014. Record warmth was spread around the world, including Far East Russia into western Alaska, the western United States, parts of interior South America, most of Europe stretching into northern Africa, parts of eastern and western coastal Australia, much of the northeastern Pacific around the Gulf of Alaska, the central to western equatorial Pacific, large swaths of northwestern and southeastern Atlantic, most of the Norwegian Sea, and parts of the central to southern Indian Ocean. The only land areas cooler than average were the Central U.S. and the southern tip of South America; no land areas were record cold. Image credit: NOAA's National Climatic Data Center.

New record set without an El Niño event
The new temperature record in 2014 was not a “cheap” record—it was set without an official El Niño event. The previous three hottest years on record—2010, 2005, and 1998—were all characterized by an El Niño event at the beginning of the year, according to NOAA’s Climate Prediction Center. During an El Niño event, warm water in the equatorial Pacific can warm the global surface temperature by 0.1°C or more, making global temperature records more likely. Admittedly, El Niño-like conditions began developing in June 2014, and the threshold for a weak El Niño event was reached in October and maintained through December. However, since there is lag of about 2 - 4 months between the emergence of El Nino conditions and the impact of this warm water on global surface temperatures (Foster and Rahmstorf, 2011), the emergence of El Niño-like conditions late in 2014 did not have a big impact on global surface temperatures. Moreover, January - March of 2014 featured weak La Niña-like conditions in the Eastern Pacific, with cooler-than-average ocean waters that helped depress global temperatures well into the summer.


Figure 3. The global departure of temperature from average from 1965 - 2014, binned by whether or not the year was classified as an El Niño, La Niña, or neutral. 2014 was by far the hottest "neutral" year on record, and the first year since 1990 to set a record without influence from El Niño. Image credit: skepticalscience.com.

UK Met Office forecasts another global temperature record in 2015
What about the new year? The UK Met Office predicts that 2015 is likely to top 2014. Assuming that the Met Office's final numbers for 2014 agree with NASA and NOAA on a global record, this forecast would make 2015 the second record-setting year in a row. The last time we saw consecutive global highs was in 1997 and 1998, when the strongest El Niño event on record gave a major boost to both years (see NOAA’s ENSO dataset). The previous pair of back-to-back record-setters was 1987 and 1988, again bolstered by El Niño conditions. A useful analog for our current situation may be 1980 and 1981. In those two years, new global highs were set without the benefit of any El Niño event. What’s more, the early 1980s marked the beginning of a dramatic rise in global atmospheric temperature that spanned nearly two decades. The rate of global warming since 2000 has been slower than in the 1980s and 1990s, but could back-to-back warmest years on record in 2014 and potentially in 2015 signal the end of this slow-down? Next week, Bob Henson will discuss new research presented at last week's American Meteorological Society meeting pertaining to this subject.

Commentary
The fact that separate analyses by three major research groups rated 2014 as the warmest year on record should put to rest the bogus idea often espoused by climate change deniers that "global warming stopped in 1998." Based on the evidence, more than 97% of climate scientists have concluded that humans are primarily responsible for the warming of the planet to the record levels observed in 2014. Climate change is already causing significant impacts to people and ecosystems, and these impacts will grow much more severe in the coming years. New research is painting a clearer picture of the tough decisions that lie ahead if we hope to reduce the serious risks that we and our planet face. As we approach the critical negotiations in Paris in December to hammer out a new binding climate change treaty, we should keep in mind that we can choose to take economically sensible steps to lessen the damage of climate change, and the cost of inaction is much higher than the cost of action.


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