We've zoomed in for a closeup of temperatures over the last three decades, taken from a longer timeline discussed here. This closeup shows the annual trend in average global air temperature, in degrees Celsius, from 1975 to 2012. For each year, the range of uncertainty is indicated by the vertical bars. The blue line tracks the changes in the trend over time. Click here or on the image to see the full graph.
(Image courtesy NOAA's National Climatic Data Center.)
Thanks in large part to the record-setting El Niño of 1997–98, the year 1998 was the warmest year globally in the 20th century. Since 2001 the global trend has been relatively flat (see graph). However, temperatures continue to run warmer than in previous decades. The global average from 2000–09 exceeds the average for 1990–99, which in turn was warmer than 1980–89. And the average for the past three years (2010–12) tops the 2000–09 average.
Although scientists are confident that global temperatures will rise further in the coming decades, there could still be occasional "pauses" in warming that last a few years, like the one we're seeing now. The most recent decadal outlook from the UK Met Office calls for a good chance that the upcoming five years (2013–17) will average warmer globally than the record year of 1998.
Some of the contributing factors to these breaks in warming could include erupting volcanoes that spew sunlight-blocking ash skyward, a lack of El Niño events, and/or the natural minimum in the 11-year solar cycle. In fact, La Niñas have predominated over El Niños during the 2010s thus far, which helps explain the lack of a new global record in the decade thus far.