acid (which refers only to the aqueous form H2CO3 in modern usage). The following formulation of Arrhenius's rule is still in use today: where is the concentration of CO2 at the beginning (time-zero) of the period being studied (if the same concentration unit is used for both and , then it doesn't matter which concentration unit is used); is the CO2 concentration at end of the period being studied; ln is the natural logarithm (= log base e ()); and is the augmentation of the temperature, in other words the change in the rate of heating Earth's surface (radiative forcing), which is measured in Watts per square meter. Derivations from atmospheric radiative transfer models have found that (alpha) for CO2 is 5.35 (± 10%) W/m2 for Earth's atmosphere. Based on information from his colleague Arvid Högbom, Arrhenius was the first person to predict that emissions of carbon dioxide from the burning of fossil fuels and other combustion processes were large enough to cause global warming. In his calculation Arrhenius included the feedback from changes in water vapor as well as latitudinal effects, but he omitted clouds, convection of heat upward in the atmosphere, and other essential factors. His work is currently seen less as an accurate quantification of global warming than as the first demonstration that increases in atmospheric CO2 will cause global warming, everything else being equal. Arrhenius's absorption values for CO2 and his conclusions met criticism by Knut Ångström in 1900, who published the first modern infrared absorption spectrum of CO2 with two absorption bands, and published experimental results that seemed to show that absorption of infrared radiation by the gas in the atmosphere was already "saturated" so that adding more could make no difference. Arrhenius replied strongly in 1901 (Annalen der Physik), dismissing the critique altogether. He touched on the subject briefly in a technical book titled Lehrbuch der kosmischen Physik (1903). He later wrote Världarnas utveckling (1906) (German: Das Werden der Welten [1907], English: Worlds in the Making [1908]) directed at a general audience, where he suggested that the human emission of CO2 would be strong enough to prevent the world from entering a new ice age, and that a warmer earth would be needed to feed the rapidly increasing population: "To a certain extent the temperature of the earth's surface, as we shall presently see, is conditioned by the properties of the atmosphere surrounding it,