08/13/2013 05:42 pm ET

Global Warming Interactives Show What Temperature Change Looks Like

From Climate Central's Andrew Freedman:

Global warming has accelerated during the past three decades, which have each been unusually warm. In fact, the most recent decade from 2001-2010 was the warmest since instrumental records began in 1850, according to the World Meteorological Organization (WMO).

While the rate of global warming has slowed in the past several years, possibly due to natural climate variability, the long-term temperature trend clearly shows that we’re living on a warming planet.

This interactive shows just how warm average global temperatures have been over the past three decades, particularly on a backdrop of warming that extends back several decades, based on data reported in a recent WMO report. It shows the global average surface temperature (land and sea) for each decade since 1880, and the dotted line shows what the 30-year average was from 1961-1990. The numbers are an average of temperature records from the three main global surface data sets kept at the U.K.’s Hadley Center, at the National Oceanic and Atmospheric Administration (NOAA), as well as at NASA.

And the warming trend is just as evident when you look at yearly temperatures and not just the decadal trends.

When you look more closely at the annual temperature record, you can see how the long-term warming trend — for the most part caused by human activities — is manifesting itself along with shorter-term natural variability in the climate system. Each of the past 27 years has been warmer than average (based on the average from 1961-1990). In fact, according to NOAA’s data set, each month for more than 28 years has had a global average temperature that was above the 20th century average, meaning that anyone younger than 28 years old has never experienced a cooler-than-average month on earth.

One of the biggest sources of natural climate variability is known as the “El Nino/Southern Oscillation,” or ENSO, which causes sea surface temperatures to warm and cool in a recurring cycle over a large area of the tropical Pacific Ocean. El Nino and La Nina events can help swing global average temperatures upward or downward with respect to their long-term average for a year or two. Typically, El Nino years are warmer than La Nina years.

What’s been remarkable about the climate of the past few decades is that even years when La Nina events took place, with their cooling influence, have still been much warmer than average. A string of La Nina events since the year 2000 has likely helped dampen global temperatures slightly, thereby slowing the increase in global temperatures. Despite the La Nina events, though, the past several years have still been among the warmest on record.

This graphic is based on data from the three major climate centers. For each data set, we calculated what the temperature anomaly was in degrees Fahrenheit relative to the 1961-1990 baseline, and then averaged the anomalies of all three data sets.


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