Nils Gustaf Ekholm

Ekholm later started to question the construction of the balloon, skeptical of its ability to keep hydrogen leakage to the minimum level necessary for the success of the expedition.

In 1899, Ekholm, an early and eager spokesman for anthropogenic climatic control, pointed out that at present rates, the burning of coal eventually could double the concentration of atmospheric CO2.

According to Ekholm, being influenced by the thoughts of his lifelong friend and colleague Svante Arrhenius, this would "undoubtedly cause a very obvious rise of the mean temperature of the Earth."

By controlling the production and consumption of CO2, he thought humans would be able to "regulate the future climate of the Earth and consequently prevent the arrival of a new ice age (Fleming 1998).

An English version published in 1901 in the Quarterly Journal of the Royal Meteorological Society[6] resulted in wide dissemination of Ekholm's ideas, including the use of the term "greenhouse" to describe the effect of carbon dioxide).