The atmosphere a shared resource

Just like the oceans, our atmosphere is one of the most important shared resources that our planet has to offer. It must not belong to anyone. It is also an active ecosystem, including a natural greenhouse effect, which makes our planet habitable by heating it by more than 30 Celsius degrees. With some ease, and in just a few decades, we have changed the atmosphere s content of one of the most important greenhouse gases, CO2, which has increased from 270 parts per million of volume (ppm) to more than 400 ppm today. A fact that demonstrates how human activity that uses the atmosphere, is using a fragile and limited resource. And it is doing so at an ever increasing rate. In the 1950s, consumption of fossil fuels accounted for 1 to 2 billion tonnes of atmospheric carbon emissions. Today, that figure is 10 billion tonnes. This additional generated CO2 is changing the composition of the atmosphere for a long time to come, for centuries. It is a cumulative process, and at the current rate we only have twenty years of emissions left to reach a situation in which the climate will be stabilised at under 2 Celsius degrees of additional warming before the end of the century.

It is necessary to put a price on carbon

If the planet s resources are a common asset, then they can no longer be used free of charge. Therefore, it has become necessary to put a price tag on carbon. But we expect this price tag to prompt a series of very different actions. The price must act as an inhibitor and encourage us to make savings in every field that produces greenhouse gases. It

must facilitate a great variety of alternative solutions. Obviously, we must reduce carbon- producing energy production methods, favouring alternative forms of production. We must control the production of cement and use alternatives adapted to each region of the world. We must regulate complex agricultural activities and the use of the soil, which can store or emit carbon, and which often emit greenhouse gases other than CO2. We must encourage solutions that protect biodiversity and do not jeopardise the supply of food to different populations. All these measures are, of course, intimately linked to changes to our planet and to any financial incentives on offer.

Putting a price tag on carbon is not an end in itself

We also need to put a price on the time we have left. We must not just go for cheaper, short-term actions, leaving structural and essential actions, such as regional development, which can take years, until the last minute. We must also take the time to research and develop, if we really want to be able to capture and store greenhouse gases on a large scale by the end of the century, something that all of the scenarios of the Intergovernmental Panel on Climate Change (IPCC) demand. Can the simple mathematics behind the notion of carbon equivalents sum all this up in a single criterion? For a geophysicist who is keenly aware of the diversity of the processes that are changing the planet, and of the diversity of the risks that these changes incur, it is difficult to conceive that cost alone, and even more so, a single price tag, can be the only means of regulating this transformation.

If the planet s resources are a common asset, then they can no longer be used free of charge. Therefore, it has become necessary to put a price tag on carbon.