I could see this one coming. While Illinois had its 6th coldest year on record, three major groups (Japan, NASA, and NOAA) have noted that 2014 was the warmest year on record. Check out this map from NOAA of the temperature departures for 2014 (red is warmer, blue is cooler). The area from the Great Lakes and southward to the Gulf of Mexico was the only place over land that was colder than average. All the other land masses and most of the ocean surface was warmer than average. In other words, relatively speaking, Illinois was one of the coldest places on earth in 2014.
Here is the time series of the global temperature since 1880 from NOAA, showing the cool 1800’s and early 1900’s before rapid warming took place through the 1940s. Temperatures stalled out for a few decades before the warming returned in the late 1970s and has continued since then. The ten warmest years on record are in the darker reds and have all occurred since 1998. By the way, scientists have been aware of the urban heat island and station exposure in general and try to account for them in these calculations.
Also, a separate group of scientists highly critical of the work of NOAA and NASA, formed Berkeley Earth, and constructed their own global temperature time series. Their results – 2014 was the warmest year on record.
The following section was updated and expanded 1/26/2015
The United Kingdom Met Office says in a press release that “2014 was one of the warmest years on record”. While tied with 2010 as the warmest year on record, they pointed out that the uncertainty in each year’s temperature makes it difficult to rank.
The European Centre for Medium-Range Weather Forecasts has been keeping track of global temperatures since 1979 and found that 2014 was in the top 10% for warmest years in their record.
And finally, here is the graph of monthly temperature departures, based on satellite data, from the University of Alabama – Huntsville that goes from December 1978 through December 2014. According to John Christy, “2014 was the third warmest, but barely” in this particular record. These data measure the temperature of the lower atmosphere, not the surface like the other datasets mentioned in this post, and require non-trivial adjustments for changes in satellites, orbital decay, etc.