How the Climate System Works

Temperature extremes have been pretty unusual across the United States so far in 2014. Looking back over this time period quickly reveals at least part of what was going on: the polar jet stream got into a serious rut.

Saturday, August 1, 2009

  • The Southern Oscillation Index tracks differences in air pressure between the eastern and western sides of the tropical Pacific.

  • (Updated June 2, 2014)

  • The total amount of water on Earth isn’t increasing, but the volume of liquid that fills the ocean is growing as ice and snow on land melt. The water is also getting warmer, which makes it expand. 

  • Human activities, mainly burning fossil fuels, are increasing the concentration of carbon dioxide in our atmosphere, amplifying the natural greenhouse effect.

  • Minimum sea ice extent observed by satellites each September has decreased by 13.7 percent per decade since the late 1970s. The seven lowest extents all occurred since 2007.

  • The Arctic Oscillation (AO) refers to an atmospheric circulation pattern over the mid-to-high latitudes of the Northern Hemisphere. The most obvious reflection of the phase of this oscillation is the north-to-south location of the storm-steering, mid-latitude jet stream.

  • Over the span of days or weeks, the strength of surface air pressure over the North Atlantic seesaws between Iceland and the Azores Islands. The shifting pressure reflects changes in atmospheric circulation that have a big impact on mid-latitude weather in the U.S. and Europe. 

  • El Niño and La Niña conditions occur when abnormally warm or cool waters accumulate in tropical latitudes of the central and eastern Pacific Ocean. The Oceanic Nino Index is the tool NOAA scienitsts use to watch for these temperature changes.