During a constant-rate climb in IMC above the freezing level, you notice that both the airspeed and altitude are increasing. This indicates the

Explanation

In a constant-rate climb, airspeed should stay constant; if it increases along with altitude, the pitot system is likely blocked (for example by ice above the freezing level), so the trapped pressure makes the airspeed indicator act like an altimeter. An unusual attitude would not produce a climb with increasing airspeed at constant power, and gyro failure does not affect these instruments.