Winters in San Antonio ain't getting warmer

Back in December of last year, San Antonio held a get-together to talk about climate change. Here is how the San Antonio Express-News reported on the event:

Attendees of San Antonio's first official event on responding to climate change came outside to find fat flakes of snow falling on downtown.

The snow served as a metaphor for weather extremes under a changing climate, something Texas Tech University climate scientist Katharine Hayhoe calls "global weirding."  Only a few days ago, San Antonio recorded a high temperature of 83 degrees, according to weather data[.] ...

"You have this natural pattern of up and down and up and down, and it's being stretched," Hayhoe said of Texas' extreme weather.

Over decades, the climate is getting hotter, she said, explaining that average annual temperatures in San Antonio since 1960 have increased 0.7 degrees per decade in the winter and 0.5 degrees per decade in the summer, leading to more warm and hot days overall and fewer cold spells.

Average annual temperatures have increased in the winter?  Something is wrong with this reporting.  By definition, an average annual temperature is the average temperature for the entire year.  It cannot be for just a portion of the year, such as winter or summer.  So we will just assume that the report should have said average winter temperatures have increased 0.7 degrees per decade, as the author of this piece indicated in some other work discussing the city's climate.  Whatever the intention, readers will be led to believe that the average temperature during wintertime in San Antonio is increasing.

...except it is not if you use the entire historical record dating back to 1887.  Actually, the trend in winter temperatures for San Antonio over the last 133 years is negative (i.e., cooler winters), although the trend is not statistically significant.  Consequently, the best way to describe San Antonio's winter temperature since the 1880s is "unchanging."  There are short-term periods of warming and cooling, but over the long-term climate record, it is unchanged.

In her report to the City of San Antonio, Hayhoe has a section entitled "How has San Antonio's climate changed?" in which she investigates what are termed "[t]he number of 'warm nights' per year, with minimum nighttime temperatures above freezing."  A large strong positive trend is reported, meaning that between 1960 and 2014 (the period over which Hayhoe chose to examine climate trends for the city), there were a lot more nights with minimum temperatures >32 degrees over time.

...except when we graph the entire historical record of minimum, nighttime temperatures above freezing for the San Antonio area since records began in 1886, the data look bizarre.  There is an increasing trend from the 1880s through the late 1930s, a sharp declining trend from the 1940s through the late 1970s, and an increasing trend since.  But overall, since the late 1880s, the trend is negative toward fewer warm nights, not more, and even after the increase in the number of warm nights since the 1970s up to the present, there are, on average, fewer warm nights in San Antonio over the past few decades than there were in most of the first half of the 20th century.  That is difficult to explain if anthropogenic climate change or municipal growth (i.e., urban heat bubble) is your mechanism for the recent increasing trend, and the longer-term historical context is needed for the City of San Antonio to understand how its residents' climate has changed, why, and where it may be headed.

Details such as these are critical to ensure that the city's limited financial resources are deployed in an effective fashion.  Climate change studies are not cheap, as is made clear from a related article in the same newspaper:

Thursday, the city of San Antonio, CPS Energy (the municipal electric utility serving the city of San Antonio, Texas) and the University of Texas at San Antonio officially begin an effort to address the causes and effects of global warming in America's seventh-largest city[.] ...

CPS Energy will provide further support and funding – $500,000 out of a $50 million pot for collaborative research with UTSA set up in 2010.  CPS has provided nearly $7.3 million in funding to UTSA for previous work on energy research.

Fifty million dollars.  That's almost real money.  Let's hope the taxpayers of San Antonio get their money's worth.

Back in December of last year, San Antonio held a get-together to talk about climate change. Here is how the San Antonio Express-News reported on the event:

Attendees of San Antonio's first official event on responding to climate change came outside to find fat flakes of snow falling on downtown.

The snow served as a metaphor for weather extremes under a changing climate, something Texas Tech University climate scientist Katharine Hayhoe calls "global weirding."  Only a few days ago, San Antonio recorded a high temperature of 83 degrees, according to weather data[.] ...

"You have this natural pattern of up and down and up and down, and it's being stretched," Hayhoe said of Texas' extreme weather.

Over decades, the climate is getting hotter, she said, explaining that average annual temperatures in San Antonio since 1960 have increased 0.7 degrees per decade in the winter and 0.5 degrees per decade in the summer, leading to more warm and hot days overall and fewer cold spells.

Average annual temperatures have increased in the winter?  Something is wrong with this reporting.  By definition, an average annual temperature is the average temperature for the entire year.  It cannot be for just a portion of the year, such as winter or summer.  So we will just assume that the report should have said average winter temperatures have increased 0.7 degrees per decade, as the author of this piece indicated in some other work discussing the city's climate.  Whatever the intention, readers will be led to believe that the average temperature during wintertime in San Antonio is increasing.

...except it is not if you use the entire historical record dating back to 1887.  Actually, the trend in winter temperatures for San Antonio over the last 133 years is negative (i.e., cooler winters), although the trend is not statistically significant.  Consequently, the best way to describe San Antonio's winter temperature since the 1880s is "unchanging."  There are short-term periods of warming and cooling, but over the long-term climate record, it is unchanged.

In her report to the City of San Antonio, Hayhoe has a section entitled "How has San Antonio's climate changed?" in which she investigates what are termed "[t]he number of 'warm nights' per year, with minimum nighttime temperatures above freezing."  A large strong positive trend is reported, meaning that between 1960 and 2014 (the period over which Hayhoe chose to examine climate trends for the city), there were a lot more nights with minimum temperatures >32 degrees over time.

...except when we graph the entire historical record of minimum, nighttime temperatures above freezing for the San Antonio area since records began in 1886, the data look bizarre.  There is an increasing trend from the 1880s through the late 1930s, a sharp declining trend from the 1940s through the late 1970s, and an increasing trend since.  But overall, since the late 1880s, the trend is negative toward fewer warm nights, not more, and even after the increase in the number of warm nights since the 1970s up to the present, there are, on average, fewer warm nights in San Antonio over the past few decades than there were in most of the first half of the 20th century.  That is difficult to explain if anthropogenic climate change or municipal growth (i.e., urban heat bubble) is your mechanism for the recent increasing trend, and the longer-term historical context is needed for the City of San Antonio to understand how its residents' climate has changed, why, and where it may be headed.

Details such as these are critical to ensure that the city's limited financial resources are deployed in an effective fashion.  Climate change studies are not cheap, as is made clear from a related article in the same newspaper:

Thursday, the city of San Antonio, CPS Energy (the municipal electric utility serving the city of San Antonio, Texas) and the University of Texas at San Antonio officially begin an effort to address the causes and effects of global warming in America's seventh-largest city[.] ...

CPS Energy will provide further support and funding – $500,000 out of a $50 million pot for collaborative research with UTSA set up in 2010.  CPS has provided nearly $7.3 million in funding to UTSA for previous work on energy research.

Fifty million dollars.  That's almost real money.  Let's hope the taxpayers of San Antonio get their money's worth.