Campernaerts (NTT Pro Cycling) set a record of 55.089km last year at the Aguascalientes Bicentenary Velodrome in Mexico, beating Sir Bradley Wiggins record of 54.526km.
Dowsett has announced he will try to reclaim the prestigious title at the Manchester Velodrome on December 12.
The former Belgian national time trial champion says Dowsett (Israel Start-Up Nation) choosing Manchester maybe prove to be the wrong decision.
"I am not a climatologist, but in Mexico the air pressure is almost constant every day.
"In Belgium or the United Kingdom, the temperature fluctuates day after day. If he has a breakdown on December 12 and there is high air pressure, I fear it will be an impossible attempt.
“I think he has a 50 per cent chance of breaking the record. I'm glad someone finally dares to do it.”
Campenaerts recently beat Dowsett in all three time trials at the Giro d'Italia, with Dowsett putting in some disappointing rides against the clock but taking a stage win on the road.
NTT's star time trial rider Campenaerts says that he chatted about the record a lot with Dowsett at the Giro: "In the last Giro d'Italia we were still talking about the Hour Record. I get along well with Alex.
"I like him, but I can't give too many tips either. He is a competitor that can take away my greatest achievement as a cyclist. If he takes my record, I plan another attack in the short term."
The main advantage Dowsett has over the Belgian is that the British rider can choose his own equipment, which is something he has done in TTs in the European and World championships, riding a Specialized bike and wearing a POC helmet instead of his standard team equipment.
Campenaerts says this is a "big advantage" but it won't be easy for Dowsett. Campenaerts says he will be sad to lose it but he will have beaten fairly with the record not being obliterated: "That would be a bit painful [losing to Dowsett], but I honestly don't believe in that. Alex faces a tough challenge. It would be sad for me if it wasn't."
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