Various people have questioned the WordWeb licensing terms. It is true that targeting flights is a very crude measure; many people's CO2 emissions come mostly from their home due to inefficient heating, insulation or air conditioning. However, the licence is designed to be easy to understand, and sufficiently simple that people will know immediately whether they satisfy it. If you break the licence you are certainly responsible for more emissions per person than are sustainable, and you can certainly afford to buy the Pro version. The licence is not telling you what to do: that is up to you, but if you don't satisfy the licence you need to pay to use the program. Emissions from international aviation are especially important as they are not covered by the COP21 Paris agreement, and could seriously undermine global efforts if not substantially reduced.
What is needed is swift and effective action at government and international levels. Climate change is the "market failure on the greatest scale the world has ever seen" [Stern 2006] - market forces and personal action alone will not solve the problem. However, personal action can help. In particular if demand for aviation can be reduced now, that will make it easier for governments to make cuts later as well as reducing a significant source of high-altitude emissions today. Cuts in emissions now will (statistically) save lives later; even the most ambitious international plan to curb emissions will not prevent a significant and damaging rise in temperature.
Temperature increases in excess of 5 degrees are quite possible if nothing is done. The Paris 2015 agreement aims to reduce national emissions substantially by 2050 aiming for a rise (well below) 2 degrees. Even the best-case scenario involves major negative consequences in a few decades, with marginal additional emissions significantly increasing the risk of additional bad effects. It is much more effective to reduce emissions early on than make huge cuts later on when the problem starts to get out of hand.
Tackling aviation growth is particularly difficult because of international agreements not to tax aviation fuel, and international aviation (and shipping) are not included in the COP21 Paris agreement. There is currently strong growth in aviation, and no cost-effective or scalable fuel alternatives. There is also considerable pricing flexibility (price elasticity of demand), meaning that prices would probably have to at least double to cut flight use in half. This corresponds to an infeasibly high carbon emission trading price. In the absence of any effective governmental legislation to restrict aviation growth, WordWeb's licence is a small way to increase the cost of flying and, more importantly, to increase awareness of the problem.
Taking numbers from the Stern Review: every medium distance flight you take now causes about 0.001 people to face starvation in the future. Roughly this means that for every hour you spend flying, someone in the future will spend an extra day short of food.
Some people feel that this has nothing to do with WordWeb, and the licensing terms are ridiculous. We agree the situation is ridiculous; the WordWeb licensing is just reflecting the current huge under-pricing of air travel. Every time you fly you are not paying the cost to the environment (and hence other people); in economics terms climate-changing emissions are an important externality leading to a market failure. WordWeb is trying to slightly increase the cost of flying via its licence to correct for this anomaly. If and when air travel is charged correctly to reflect the total cost, which is much the most efficient solution, the WordWeb licence will be changed to a more sensible economic model. We focus on air travel, since most other emissions from individuals are covered by the Paris agreement.
The licence also has the advantage that people who cannot easily afford to pay can use the program for free. If you can afford to fly, so that you do not satisfy the licence, you can afford to buy the program.