Each business sector should be considered as a global unit when being counted for CO2 emissions.

"Secondly, if you count and cap emissions of a business sector globally you actually encourage businesses to shift these global emissions to where it is cheapest to spew them" 
 
If it costs the same globally it would not be cheaper to spew emissions here rather than there.  
 
Your suggestion would cut down demand for Chinese products which would only give china more incentive to produce cheaply , which would mean more pollution. 
 
Caps are specific, not indirect ways/means of getting pollution cuts and should be far more effective than the surreptitiously ban Chinese products plan.  

First of all, multinationals have complex schemes for deciding where to operate and carbon tax is only one -usually small, seldom significant- among many factors considered in business relocation. Political and macroeconomic stability, market size, ease of doing business, transport infrastructure... all these count more than a potential carbon tax on decisions to relocate.

Secondly, if you count and cap emissions of a business sector globally you actually encourage businesses to shift these global emissions to where it is cheapest to spew them. And, my argument goes, counting emissions at a business sector level creates dilemmas over, e.g. how much should shipping be allowed to emit globally compared to the beverage industry. Does that matter?

Moreover, establishing a global cap on emissions for each multinational is not practical because some companies grow naturally while others die out. Deciding on a global cap per unit of output/ value added for a category of goods or services (that is what a business sector ultimately is) puts poor and less technologically advanced countries at a disadvantage far beyond problems with relocation.

I have a different suggestion: China is the largest emitter of greenhouse gases in the world. Half of its emissions are related to exports. Now think about European importers fo Chinese goods. Establish a carbon tariff, increase the prices of goods made in China with the cost of their carbon footprint (global or EU price level) and charge this to the final European user -if final consumption picks up the tab, which is the case with carbon taxes.

Opinions?