These bullet points are taken from the Part I report about climate change in Iowa, by Iowa State Climate Science Program director, Eugene S. Takle:
- Iowa has had an 8% increase in annual average precipitation over the 136-year period from 1873-2008. Climatological patterns of precipitation for Iowa consist of an east-west gradient, with drier conditions to the west and wetter to the east, and a somewhat wetter pattern to the south and slightly drier to the north.
- Since 1970, Iowa (and the central US) has experienced a declining number of extreme high summer temperatures, a feature of summer climate that seems counter to global and continental trends.
- The number of frost free days has increased by 8-9 days over the 116-year period from 1893-2008.
- Iowa’s annual average temperature has increased since 1873 at a rather modest rate, but seasonal and day-night changes are proportionately larger and have higher impacts. Temperatures have increased six times more in winter (0.18°F/decade) than in summer (0.03°F/decade), and nighttime temperatures have been increasing more than daytime temperatures.
- Models, which 20 years ago correctly projected polar regions to warm more than equatorial regions, minimum daily temperatures to rise more than maximum temperatures, and US winter temperatures to increase more than summer temperatures – indicate that the current trends likely will continue.