In an article from the Huffington Post, the writers at Climate Central – "an independent organization of leading scientists and journalists researching and reporting the facts about our changing climate and its impact on the American public" – claim the following:

Average Summer Temperatures Have Risen In Every Region Of The U.S. Since 1970

The piece by Climate Central – which receives significant government funding and has a number of federal government and academic scientists on its "science" team – goes on to state that "summer temperatures have been steadily rising since 1970."  Steadily rising since 1970?  Not a chance.

The following table shows the trends in "average summer temperatures" for the nine U.S. climate regions and lower 48 states since 1970, as well as the trends over the past two and three decades.

Click to enlarge.

Choosing 1970 as a starting point for a temperature time series in the USA is most favorable for the climate alarmists, since the 1970s represent the cool trough between two higher temperature peaks in the 1930s and the present.  Think of choosing 1970 to start your annual analysis just like choosing the wintertime period to start a monthly temperature analysis.  If you start in the coldest period, the odds of finding an increasing temperature trend are high.

Regardless, only six of the nine climate regions have statistically significant warming trends since 1970.  That certainly isn't consistent with the title of an article that claims that "average summer temperatures have risen in every region of the U.S. since 1970," is it?  And only 32 of the 48 states have significant warming trends over this period.  That isn't every region, either.

Over the past three decades – a timeframe that climate scientists apparently prefer and think is appropriate for trend analysis – only three of the nine climate regions (i.e., one third) and only 14 of the lower 48 states (29 percent) have significant increasing trends in average summer temperatures.

During the past two decades, none – I repeat: none (aka zero percent) – of the nine American climate regions, and only two of 48 states (4 percent), have significant increasing trends in average summer temperatures.  This pattern doesn't sound consistent with claims that "summer temperatures have been steadily rising since 1970."  If temperatures were indeed rising steadily, the trends would be significant not only since 1970, but over both the last two and three decades as well.

Overall, summer temperatures have been increasing in only about two thirds of the United States since 1970.  The last three decades have seen only about one third of the U.S. warming during the summer, and over the last two decades, almost all of the nation has not – repeat: not – seen summertime warming.  Reality is a long way from the claims in this Climate Central article.