The last few of these natural cycles have recurred roughly every 100,000 years. The largest global-scale climate variations in Earth’s recent geological past are the ice age cycles (see infobox, p.B4), which are cold glacial periods followed by shorter warm periods. Source: Based on figure by Jeremy Shakun, data from Lüthi et al., 2008 and Jouzel et al., 2007. ( larger version) Atmospheric CO2 concentration surpassed 400 ppm in 2016, and the average concentration in 2019 was more than 411 ppm. As the record shows, the recent increase in atmospheric CO2 concentration is unprecedented in the past 800,000 years. During these cycles, changes in CO2 concentrations (in blue) track closely with changes in temperature (in orange). The cyclical pattern of temperature variations constitutes the ice age/ interglacial cycles.

The current CO2 concentration (blue dot) is from atmospheric measurements. CO2 is measured inĪir trapped in ice, and is a composite of the Dome C and Vostok ice core. Temperature is based on measurements of the isotopic content of water in the Dome C ice core. Data from ice cores have been used to reconstruct Antarctic temperatures and atmospheric CO2 concentrations over the past 800,000 years.

Time changes