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Averaged over all land and ocean surfaces, temperatures warmed roughly 1.53°F (0.85ºC) from 1880 to 2012, according to the Intergovernmental Panel on Climate Change (see page 3 of the IPCC's Climate Change 2013: The Physical Science Basis, Summary for Policymakers - PDF). Because oceans tend to warm and cool more slowly than land areas, continents have warmed the most. In the Northern Hemisphere, where most of Earth's land mass is located, the three decades from 1983 to 2012 were likely the warmest 30-year period of the last 1400 years, according to the IPCC.
The graph above clearly shows the variability of global temperature over various time intervals (such as year to year or between decades) as well as the long-term increase since 1880. The full 2013 Working Group 1 report addressed in detail the slowdown observed in the rate of warming since the late 1990s. (For more, see the FAQ entry: "Hasn't Earth been cooling since 1998?")
There are slight differences in global records between groups at NCDC, NASA, and the University of East Anglia. Each group calculates global temperature year by year, using slightly different techniques. However, analyses from all three groups point to the decade between 2000 and 2009 as the hottest since modern records began more than a century ago. Temperatures in the 2010s have been running slightly warmer still.
The year 2013 tied with 1980 as the 34th warmest in 120 years of data for the contiguous 48 U.S. states, according to the National Climatic Data Center (NCDC). This comes two years after the record warmth of 2012, which was substantially warmer—a full degree Fahrenheit (0.6°C)—than any other year since national records began in 1895. The U.S. warming rate of about 1.3°F (0.72°C) per century (blue line in the graph at bottom right) is roughly comparable to the global rate of warming (see above).
Despite some cooler years from 2008 to 2010, the decade as a whole (2000–2009) was the nation's warmest on record, with an average temperature of 54.0°F. In contrast, the 1990s averaged 53.6°F, and the 1930s averaged 53.4°F.
The first four years of this decade (2010–2013) were slightly cooler on average than 2000–2009 for the United States, with an average of 53.5°F. The United States covers only about 2% of the globe's total surface, so there can be noticeable differences at times between U.S. and world temperature trends. Overall, global readings this decade are running warmer than in the 2000s.