Air France repeat? - blocked pitots (ice) during attempted climb above Cb. Static pressure falls with altitude causing over reading airspeed. Raise nose to contain erroneous speed indication = stall hence the slow reported groundspeed.
Actions: -
1. Ignore speed - press EMER CANC to kill the o/speed warning noise.
2. Fly power / attitude - Best is 2 degrees nose up and 78% N1 or my favorite Thrust idle and level attitude or just below and decent. Going for 5 degrees nose up and climb power iaw QRH won't work that high.
3. Turn off all ADRs to bring up BUSS (Back-up speed scale) if fitted on PFD to show AoA.
4. Do nothing else until clear of weather.
5. Companies have been hammering unreliable airspeed to death (no pun intended) in every sim since Air France.