Do you count your carbon?

If you knew a product's carbon footprint, would it influence what you buy? Could carbon-labelling help reduce a country's greenhouse gas emissions?

Tesco and other British high street multiples are introducing carbon labelling on selected products, and the Japanese government recently announced something similar.

But, I'm not convinced that this carbon labelling will work.

First, counting carbon (and the other greenhouse gases) isn't easy: accurate calculations are difficult to come by, and specific to each context (change what you feed the chickens on a particular farm, and the carbon count for the supermarket chicken korma dinner changes dramatically). Then, there is the problem of what to include -- only carbon? Other greenhouse gases? And how do we take account of the 'virtual water' contained in products?

Food product labels are already littered with data (calories, 'nutritional' information, and 'may contain nuts' allergy warnings . . .) and at a time when shoppers are probably most interested in what something costs.

Printing calorie information on food products hasn't exactly stemmed the rise in obesity. And if we can't as a nation manage a lo-cal diet, what chance for a lo-CO2 one? Meanwhile, Tesco has just announced a big drive to introduce yet more cheap ranges of low-cost products. Guess we can say goodbye to the organic aisle.

Hotel towels and 'green wash'

Hotels worldwide have cottoned onto the benefits of not changing guest towels every day. Usually, there is a sign inviting us to join them in doing our bit to help the environment.

But are they really helping the environment? Or hoping to save money on their laundry bills?

I've been pondering this since reading about how hotels can make their 'towel reuse signs' more effective by wording them carefully. You can read about the study in the enjoyable and generally thought-provoking book Yes! 50 secrets from the science of persuasion.

Sure, less laundry is 'a good thing' -- it translates into less water wasted, less energy and detergents used, and less linen trucked around the place. But let's have a little honesty here.

I have yet to see a hotel announce that, thanks to guests reusing their towels, the company saved €xxx on its laundry bill last year, which it donated to a named environmental charity*, and with your help they'll save, or 'raise', even more this year.

Now, that's a wording that would really convince me not just to reuse my towels -- but even bring my own.

*With the receipt displayed proudly in the hotel lobby

Motoring tips from Ryanair?

It's not often we agree with Ryanair's environmental strategies. And no, we don't know about the safety implications of asking pilots to carry at most 300 kg of extra fuel (nothing about it on Ryanair's news page, so here's an Irish Times report).

But carrying extra fuel adds to the weight of any vehicle, so it makes fuel-efficiency and environmental sense to carry as little as possible. Which is why motorists should take Ryanair's recommendation on board.

Driving with a tank full of petrol means you get fewer kilometres per litre when your tank is full, it costs you money, and your car produces more pollution for every mile that you drive.

If the price of petrol dropped after, say, the first 25 litres, then it might make sense to bulk buy. But it doesn't. Instead, your fuel efficiency drops. Put another way: bulk buying is costing you money. Better to half-fill the tank instead.

The latest in environmental tourism?

It would take the French.

A tethered gas balloon in Paris's 15th arrondissement has been taking tourists up for aerial views of the city since 1999. Now, it has been coupled to an air quality monitoring and display system, to give real time information on air quality in the city and at major traffic junctions.

Sensors will monitor levels of nitrogen dioxide, ozone, and particulate matter. And, if we understand this correctly, 'Ballon Air de Paris' will change colour depending on air quality: red for highly polluted air, through to yellow for 'mediocre', and green for very clean.

Perfect, you'd have thought, for keeping an eye on air quality in Beijing in the run up to the Olympics? No, you're right. It would never take off!

How many people are there in the world?

6,681,394,380 . . . and counting . . . rather fast.

Today, July 11, is World Population Day, inaugurated in 1988 by the United Nations to mark the day when the world's population hit five billion, July 11, 1987.

The counter is at www.worldometers.info, where we learn that the absolute growth in population today (at the time of writing) is 135,468. Watching all the numbers spin around can be mesmerising. And worrying.

Some of the counters clock up slowly -- the number of women who died in childbirth, for instance, although that depressing total is already over 330,000. Reassuring, on the other hand, if we can believe the statistics, that world expenditure on education is nearly twice military expenditure.

Other eye-catching comparisons: as a committed city cyclist, it's nice to see that twice as many bicycles have been produced as cars this year, although I'm intrigued to see that there are three times as many computers as bicycles.

And can there really be nearly half a million new book titles so far this year? (Enough to humble any author who will soon be adding to the pile!)