FALSE GPWS WARNING CAUSES MLG TO CLB FROM 6000 FT TO 7300 FT IN IMC.

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AT 6000 FT ON ASSIGNED HDG 180 DEGS; GPWS SOUNDED WITH 'TERRAIN; TERRAIN; CLB; CLB.' WENT MAX PWR AND TOOK OFF ALT AND PITCHED TO ABOUT 20 DEGS (250 KTS). GPWS SOUNDED SEVERAL MORE TIMES THEN SILENCED. I STOPPED THE CLB AT 7300 FT. FO TOLD ATC WHO SAID COME BACK DOWN TO 6000 FT WHEN ABLE. ALTHOUGH I 'KNEW' THERE WEREN'T 6000 FT MOUNTAINS; I THOUGHT MAYBE I HAD MISREAD THE ALTIMETER OR MAYBE ALTIMETER SYS HAD FAILED. THINKING BACK; RADAR ALTIMETER HAD 'FLUTTERED' UP TO PLUS OR MINUS 1000 FT PRIOR (DON'T KNOW HOW PRIOR). THIS OCCURRED ABOUT OVER CIA BUILDINGS. IF THEY RADIATE ELECTROMAGNETIC 'STUFF' (I'M A BUSINESS MAJOR; NOT ENGINEERING!) THAT AFFECTS OUR ACFT SUCH THAT WE HAVE TO IMMEDIATELY LEAVE ASSIGNED ALTS; ESPECIALLY IN AS CONGESTED AN AREA AS THE DC AREA; WE COULD CERTAINLY HAVE MIDAIR COLLISIONS (NOT TO MENTION ATC CTLRS AND PLTS WITH MORE GRAY OR MISSING HAIR). WE DID TELL THE CTLR ASAP BUT WITH FREQ CONGESTION; ETC; IT TOOK WAY TOO LONG FOR HIM TO DO ANY CTLING. I ASSUME THE CIA WOULD DENY EVERYTHING BUT JUST THE QUESTION TO THEM MAY MAKE THEM CHK INTERNALLY.