The tropopause has risen by an average of 650 feet globally in the last 22 years because of global warming and ozone depletion, according to a study published in the latest issue of the Journal of Geophysical Research. For those of you who’ve forgotten your junior high school science, the tropopause is the atmospheric layer above the troposphere (which swaddles the Earth) and below the stratosphere (where commercial jets fly). According to the research, which was conducted by 12 experts from around the world, greenhouse gases created by the burning of fossil fuels warm the atmosphere and cause the troposphere to expand, much as a balloon filled with cool air will expand when heated. As the troposphere expands, it forces the tropopause upward. At the same time, the breakdown of the ozone layer is causing the stratosphere to cool and contract, which pulls the tropopause up further. The scientists say the height of the tropopause could be a useful litmus test for the human impact on climate, but they acknowledge that it’s too early to know what effects the changing height will have on the Earth’s weather patterns.