David J. Travis of the University of Wisconsin-Whitewater and his colleagues collected three decades of temperature data from nearly 4,000 weather stations across North America for the three-day periods before, during and after the air traffic moratorium. By comparing the so-called diurnal temperature range (DTR), which is the difference between daily highs and nightly lows, the team calculated that the range of temperatures was more than one degree Celsius greater in the absence of commercial air traffic. This increase was even more pronounced in regions reported to have the most contrail abundance, such as the midwest, northeast and northwest sections of the country.
Cloud cover (particularly high-level cirrus clouds that are primarily composed of ice crystals) insulates the planet by reflecting incoming radiation from the sun and trapping outgoing infrared radiation. Contrails, the researchers conclude, exacerbate this effect.