At first reading this seems a fair question, but when you consider it you soon realise it's not going to get an accurate answer nor, equally importantly, will the answer be informative. But if you are to pursue it, the first clarification is to establish what is meant by 'produced'? I assume, since all organic matter produces CO2, this really means how much man-made CO2 is produced. But that still leaves the simple fact that pretty much everything we do, everything we produce and everything we consume has a carbon footprint.

Take cars for example. The following came from wiki.answers.com:

The average passenger vehicle produces 5.2 metric tons of Carbon Dioxide per year. Given 250 million cars in the USA, that equals 1 Billion 300 million (1,300,000,000) Metric Tons per year. Given 800 million cars globally, that equals 4 billion 160 million (4,160,000,000) Metric Tons per year.

Great - we'll have to substantiate the numbers and assumptions but there's an answer - 4Bn tonnes p.a for private cars. Not freight, trains, planes, or shipping, just passenger cars. Divide by 8760 (hrs per year) and you get 47.5m tonnes p/hr.

That still leaves researching all the other types of transport mentioned above, before moving on to, say, energy use i.e. electricity, gas. This will be more complex since electricity already has a small element of carbon-neutral sources i.e. hydro, solar, wind, nuclear. However, a quick search suggests that global electricity use in 2008 was a rounded up 17TW (trillion watts). All that's needed is the average CO2 produced per watt globally - for the UK its 560g CO2/kWh - and, voila, another step towards the total.

Now I'm not convinced this is useful since it risks double-counting as you work through manufacturing, construction, and distribution. By contrast, the co2/kWh figure is interesting since it means you could readily calculate how much Co2 is produced per person as a result of energy consumption, and that's meaningful and relevant to everyone.

I wish you all the best in your academic challenge but personally I'd change the question.