NASA FACTS 1998 (p.3): "The temperature record of the past hundred years does show a warming trend, by approximately 0.5°C. However, the observed warming trend is not entirely consistent with the carbon dioxide change. Most of the temperature increase occurred before 1940, after which Earth started to cool until the early seventies, when warming resumed. Carbon dioxide, on the other hand, has been increasing steadily throughout the past century."
NASA FACTS 2002: "Far from being some future fear, global warming is happening now, and scientists have evidence that humans are to blame. For decades, cars and factories have spewed billions of tons of greenhouse gases into the atmosphere, and these gases caused temperatures to rise between 0.6°C and 0.9°C (1.08°F to 1.62°F) over the past century. The rate of warming in the last 50 years was double the rate observed over the last 100 years. Temperatures are certain to go up further."
"Most of the temperature increase occurred before 1940" is mathematically incompatible with "The rate of warming in the last 50 years was double the rate observed over the last 100 years". That is...unless the temperature records changed in the four year interim. Oh wait, they did: