I'd like to see your evidence for this. Catalytic converters work once their temperature gets above 200C and that happens typically when the engine itself gets to temperature. So on a 30 minute journey you might have 5 mins of emissions and 25 mins of clean air. No way would it take 15 mins to get to operating temperature. In short removing the cat is like removing baffles or the flapper valve - an antisocial modification done because you want to be awkward and to irritate non bikers with extra noise.
Either I'm not making making myself clear enough - or you're the one who's being awkward.
To re-illustrate my point: modern catalytic convertors consist of a very fine honeycomb matrix which, because of it's large surface area, must be housed using methods which address Bernoulli's principle in precisely the wrong way.
I'll spare you a blow-by-blow technical explanation, but what you're doing by introducing a cat is disrupting the momentum and free flow of escaping exhaust gasses. This increases their density by lowering their velocity, thus allowing more time for the heat carried by said gasses to be dissipated through the exhaust system, which increases gas density even more.
All these things increase exhaust-system back-pressure, reducing the ability of the engine to effectively clear itself of exhaust.
So in simple terms, you're placing a drag on the engine, which means it can only produce the same power by doing more work.
And the rider can only facilitate the needed power increase in one way: by opening the throttle wider to give the engine more fuel.
Hence the increase in
overall emissions.
As for the rest: Petrol engines produce two major waste products: carbon dioxide and water.
The 'harmful' level of unburned hydrocarbons falls to almost nothing after the time it takes for a well-tuned engine to warm up.
Nitrogen oxides are another special case - but they only come about when combustion temperatures are excessive for long periods of time.
So for the most part, a catalytic convertor steps in and tries to do a job the engine is already doing quite well by itself. Talk about helping someone search their own trouser pockets for change!
Go to a second-hand bookstore and pick up a textbook on A-level physics and chemistry. Chances are you'll see everything I've just said.
Cats are NOT a solution. They are a figleaf. Another guise for the rapidly-spreading cancer of political correctness.
There is another side to this fascinating story - but let me not go into an explanation of the tremendous energy consumption, acidic extraction processes and bargain labour exploited in my fair country to get the platinum required to produce cats, so that Europe and America can stare at the rest of the world from atop their moral high horse.