Question

Passage:
In 1896, Swedish scientist Svante Arrhenius proposed one of the earliest quantitative models evaluating the influence of atmospheric carbon dioxide ($CO_2$) on surface temperatures. Arrhenius calculated that halving atmospheric $CO_2$ would trigger widespread glaciation, whereas doubling it would significantly increase global temperatures. However, his hypothesis faced swift criticism from physicist Knut Ångström in 1900. Ångström conducted laboratory experiments suggesting that atmospheric $CO_2$ absorption bands were already saturated, meaning that adding further $CO_2$ would absorb virtually no additional infrared radiation. Furthermore, ��ngström argued that overlapping absorption spectrum bands between water vapor and $CO_2$ rendered any temperature fluctuations attributable primarily to humidity variations rather than carbon concentrations.

Subsequent mid-twentieth-century research demonstrated that Ångström's conclusions were flawed because his laboratory tests were conducted exclusively under sea-level atmospheric pressures. At higher altitudes in the upper troposphere, lower pressure and reduced water vapor concentration narrow the absorption spectral lines, allowing additional $CO_2$ to absorb infrared photons effectively. Nevertheless, during the early twentieth century, Ångström's saturation argument led mainstream climatologists to discount Arrhenius's greenhouse calculations for nearly five decades.

Statement to evaluate:
Based on the passage, Knut Ångström's 1900 critique of Arrhenius's greenhouse model was based on all of the following arguments EXCEPT the assertion that reduced atmospheric pressure at high altitudes alters infrared spectral line absorption.