Temperatures in 2012 did indeed break all previous records by nearly a full degree, as the National Oceanic and Atmospheric Administration announced a few weeks ago.
The graph shows the average temperature across the Lower 48 U.S. states going back to 1890, when careful records began to be kept. The range is between 50 and 56 degrees Fahrenheit. The graph was definitely lower before 1918, but despite all the concern about global warming arising in the 1990s, the truth is that the range did not change much until 1998. After that there was a distinct upward racheting for the first decade of the 21st century. Temperatures fell back to near the normal range in 1998 but now they have jumped up again to a level never before seen. The decisive factor last year was a warm March that exceeded all previous records.
The bar chart at the bottom measures the Palmer Drought Severity Index, measured as moderate, severe and extreme. The worst period was the Dust Bowl Era of the 1930s, although the 1950s also experienced a long drought that doesn't get the same attention. Periods of low rainfall have actually grown less frequent but last year's matched the worst ever except for the monumental year of 1936. Improved farming techniques have limited the effects of low rainfall but the ijmpact on crops and food prices has still been significant.
Was last year’s jump in temperature just an outlier or the beginning of a new upward trend? One way or another, it’s getting harder and harder for global warming skeptics to deny a pattern of change.