Our Changing Climate

 
  June 30, 2010. Polar Bear at Pittsburgh Zoo. Photo by ChubbyWimbus at wts wikivoyage [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

June 30, 2010. Polar Bear at Pittsburgh Zoo. Photo by ChubbyWimbus at wts wikivoyage [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Impacts on Temperature

• Temperatures in Pennsylvania have increased more than 1.8 degrees Fahrenheit in the past 110 years [1]. Pittsburgh is also experiencing, on average, nearly six more days per year above 90 degrees Fahrenheit than in 1970 [2].

Climate models project that during mid-century (2041-2070), Pittsburgh’s temperatures will closely resemble those found historically in the warmer Washington – Baltimore metro areas. Mean warming across the state may be in the 5.4 to 6.3 degrees Fahrenheit (3.0-3.5 degrees Celsius) range [3].

One study found that Pittsburgh’s temperatures may increase by 0.5 Fahrenheit per decade between 2011 and 2040 and increase even faster by 1 degree Fahrenheit per decade between 2040 and 2099 [4].

The number of days above 90 degrees Fahrenheit each year may increase from nearly a dozen now to over 30 days by 2050 – and over 70 days by the end of the century [5].

  July 2013: Severe Thunder Cloud. Photo by Musician186 (CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons Licence

July 2013: Severe Thunder Cloud. Photo by Musician186 (CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons Licence

Impacts on Extreme Weather

Pittsburgh and surrounding areas are no strangers to flooding. Devastating floods occurred in 1907 and 1936 [13]. On August 19, 2011, two separate storms producing up to 6 inches of rainfall through parts of the Pittsburgh metro area led to flash flooding that contributed to the deaths of four people. During the evening commute, the second of the storms produced over 2 inches of rainfall in one hour [14].

An unusual storm system more typical of a winter storm than one found in late summer brought widespread 3—5 inch rainfall totals with locally higher amounts that led to significant flooding in southwestern Pennsylvania and adjacent areas of West Virginia and Maryland on July 28 and 29, 2017. The flooding closed roadways and forced evacuations and numerous water rescues in the region, including in Pittsburgh [15].

  February 8, 2010: Blizzard in Pittsburgh. Photo by Christopher Rice, (CSC_0146) [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

February 8, 2010: Blizzard in Pittsburgh. Photo by Christopher Rice, (CSC_0146) [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

Impacts on Precipitation

There has been a 10 percent increase in annual precipitation in Pennsylvania over the past century. Projections through mid-century suggest a continued rise in very wet months (where precipitation is greater than 150 percent of the 1981- 2010 normal), with an annual precipitation increase of 8 percent and a winter increase of 14 percent [6].

The risk for extreme precipitation events and flooding will also increase, [17] exacerbating the already dangerous and deadly episodes of flash floods that have hit western Pennsylvania. [18]

The Northeast, including Pennsylvania, experienced a 71 percent increase in the heaviest (defined as the heaviest 1 percent of all daily events) daily precipitation events between 1958 and 2012 [7].