There were actually some good theoretical reasons for thinking that; the paradigm was that if there was enough carbon around, C|O.sub.2~ would simply accumulate in the atmosphere until enough of a greenhouse effect built up, turning Mars into a moderately earthlike planet."
"We realized that there is a limit at which the greenhouse effect doesn't work anymore because the C|O.sub.2~ begins to condense out of the atmosphere." With the new models, Kasting saw that all the early Mars calculations were too optimistic about greenhouse warming.
In some ways, says Karoly, these patterns are consistent with trends expected from the greenhouse effect
. But he stresses that other factors, including ozone loss in the stratosphere, could cause the temperature changes he observed.