and why do they all go the same direction, up? >> because, they what are is called parameterized. they're all parameterized, can i translate parameterized in english? fudge. they don't get the right answer, don't know the right answer for certain phenomena, so we essentially put in code steps that give us what we think it should be. and systematic error that was made was the models were tuned, as it said. tuned. tuned to simulate the warming of the early 20th century. began in 1910, ended in 1945, about .45 degrees celsius. mark, that could not have been caused by carbon dioxide. mark: because there wasn't enough. >> we had to put enough in that the background carbon dioxide concentration is 280 million parts per million. when the first warming started,