The year 2014 ranks as earth’s warmest since modern record keeping began, according to two separate analyses by U.S. scientists. Nine of the 10 warmest years in the instrumental record have now occurred since 2000; the tenth was in 1998. This trend continues a long-term warming of the planet, according to an analysis of surface temperatures by the NASA Goddard Institute of Space Studies (GISS), an affiliate of Columbia University’s Earth Institute. In an independent analysis of the raw data released at the same time, the National Oceanic and Atmospheric Administration (NOAA) also found 2014 to be the warmest on record. A separate report based on the GISS data was also released by the Earth Institute.
“This is the latest in a series of warm years, in a series of warm decades. While the ranking of individual years can be affected by chaotic weather patterns, the long-term trends are attributable to drivers of climate change that right now are dominated by human emissions of greenhouse gases,” said GISS director Gavin Schmidt.
The U.S reports follow similar findings announced earlier this month by the Japan Meteorological Agency, and preliminary analyses released in December by the United Kingdom Met Office and the World Meteorological Organization. There are subtle differences in the way each agency processes temperature data, but they are all in broad agreement. The reports all undercut climate skeptics and politicians who have claimed that global warming stopped after around 1998.
Since 1880, when consistent modern records started becoming available, earth’s average surface temperature has warmed by about 1.4 degrees Fahrenheit (0.8 degrees Celsius), a trend largely driven by the increase in carbon dioxide and other human emissions into the planet’s atmosphere, say climate scientists. The majority of that warming has occurred in the past three decades. The previous top records for warmest year were set in 2005 and 2010.
A few skeptics pointed out that 2014 exceeded the previous records by only a few hundredths of degree Celsius, and thus did not indicate a trend. However, most who reviewed the results said the continuing run of record-setting years was a clear sign that there has been no pause in global warming.
While 2014 temperatures continue the planet’s long-term warming trend, scientists still expect to see year-to-year fluctuations in average global temperature caused by phenomena such as El Niño or La Niña. These phenomena warm or cool the tropical Pacific and are thought to have played a role in the flattening of the long-term warming trend over the past 15 years. However, 2014’s record warmth occurred during an El Niño-neutral year.
“Record warmth at a time of only marginal El Niño conditions confirms there is no hiatus in global warming,” says the report of the Earth Institute’s program on Climate Science, Awareness and Solutions. “Global temperature in 2015 may further alter perceptions.”
Map of the 2014 global temperature anomaly. NASA/GSFC/Earth Observatory, NASA/GISS
Different regions are still strongly affected by short-term weather dynamics, so the effects are not uniform. For example, in the United States in 2014, parts of the Midwest and East Coast were unusually cool, while Alaska and three western states – California, Arizona and Nevada – experienced their warmest year on record, according to NOAA. There was also record warmth in parts of the Pacific, Australia and across much of Europe.
The GISS analysis incorporates surface temperature measurements from 6,300 weather stations, ship- and buoy-based observations of sea surface temperatures, and temperature measurements from Antarctic research stations. This raw data is analyzed using an algorithm that takes into account the varied spacing of temperature stations around the globe and urban heating effects that could skew calculations. The result is an estimate of the global average temperature difference from a baseline period of 1951 to 1980. NOAA scientists used much of the same raw temperature data, but a different baseline period. They also employ their own methods to estimate global temperatures.
NASA monitors earth’s vital signs from land, air and space with a fleet of satellites, as well as airborne and ground-based observation campaigns. “The observed long-term warming trend and the ranking of 2014 as the warmest year on record reinforces the importance for NASA to study earth as a complete system, and particularly to understand the role and impacts of human activity,” said John Grunsfeld, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington.
