gums
Here is what can happen when the pitot tubes
start to ice over and the pilots respond to the false (higher) speed/climb rate readings by throttling back. In this case it is pre-computer age.
http://www.airdisaster.com/reports/ntsb/AAR75-13.pdf
However,
All of us that have flown into CB's or had a pitot-static ice problem and simply held attitude and didn't chase speed or altitude until we figured out our problem. Keep wings level and a semblance of level attitude.
seems so right, if one recognizes the situation.