Twenty years ago, at the Rio 92 summit, the first foundations were laid for tackling climate change. How do you value what you've done since then?

We had to do a lot more. Politicians have not soaked as much as they had to wet. However, another reading must be made: it is very difficult to implement multilateral systems in the world. Do we have another system? No. We do not have a global environmental organization dealing with these issues, which can force countries to do this or that. Therefore, one part of the assessment is that much less has been done than had to be done, and another part is that the multilateral system we have is not the best, but mere maintenance is triumph.

The commitments made under the Kyoto protocol have not been fulfilled, but, in any case, was the starting point good? The target was for emissions to reach 95% of 1990 by 2012. Was that enough, even if it had succeeded?

No, it wasn't that much. But Kyoto is the first political step. Now comes the second stage, and the only ones who agree to implement it are the European Union, Liechtenstein, Belarus, Norway and Ukraine.

Discharges for this period will take place at the December congress in Doha.

Yes, and you can predict what kind of meeting you're going to have. The Copenhagen Summit in 2009 was a great defeat. Political commitments were made, but not legal ones. And at the recent meeting in Bangkok it has been seen that no one is prepared to meet the levels of landfill agreed in Copenhagen. Towards Doha, underdeveloped countries are pushing for Clean Development Mechanisms (CDM). GGM allows developed countries to invest in programmes that reduce gas emissions in non-developed countries, giving them credit for continuing emissions in their countries. In Bangkok, the undeveloped countries, seeing that the political promises of Copenhagen are not going to be fulfilled, began to threaten the breakdown of the GGM.

However, GMMs have not managed to reduce their emissions.

Ethically, GGM is like buying the jaw. In any case, we have to recognise that climate change is global and that emissions here and there are the same. First of all, we have to assume that the aim is to put a barrier to discharges. How can we ensure that this barrier is not overcome? That is the second step. To do so, you can create markets, you can create emissions trading. It's a good idea scientifically. We criticize the dumping becoming merchants, but if that can help not overcome that barrier, welcome.

Does the barrier of dumping have to be established by politicians?

There are scientific studies, and then politicians decide where to set the limit. It is scientifically said that if the Earth heats up more than two degrees, there would be serious problems. The political goal is not to go from two degrees to two degrees, but for many scientists climbing two degrees is a tremendous barbarity, because they believe that nothing, or very little, should be raised. Politicians know that we are at an irreversible stage, that warming is taking place, and on an accelerated basis. So what we have to achieve now is not to go through those two grades, and that is what was decided in Cancun. Politically and scientifically we can no longer defend “climate change no”. It's happening, and we've already bought the card to continue with climate change over the next 50 years. By 2050, a reduction in CO2 emissions of 90-95% would be required in order not to exceed two degrees. In other words, reduce emissions to 10% of current emissions.

But that will not be possible.

In the United States, in the United Kingdom -- they start saying it wouldn't be a bad idea to start discussing the three grades. And the third world says, no, two degrees and a half, we're already experiencing climate change, and we're going to suffer it in the next few decades, because even if there's a 90 percent drop, we're going to get to two degrees. Since Copenhagen, the developed countries have been politically committed. Even if these commitments had been met, the world would heat three degrees to 2100. Compromises are not enough to stop the rise by two degrees. No one believes that they will be met, but we are on a three-degree hike, because commitments do not represent a 90% cut. Finally, the EU has announced an 80% drop by 2050. You said it, yes, but ...

The energy model is at the heart of the debate. In this respect, the development of renewable energy is a fundamental element. But can renewables solve the problem?

We can't think that with the fetishism of economic growth that we have in this world, that's going to bring us welfare. We need to talk about sustainable renewable energies. Being renewable does not mean that they are ecologically sustainable. Wind farms everywhere, is that sustainable? Can we maintain the current economic model with renewables? Technically, I don't know, I don't know what the consequences would be. But the question should not be that, but how we should change the economic model, leaving aside the fetishism of growth, and in that transformation renewables, one cannot go without the other.

Can effective action be taken against climate change if the economic paradigm is not changed?

I am sure not. Look, we'll change the model, that's clear, the question is how. We should control that change, so that it's smooth, or we're going to hit a big deal.

How will that blow be carried out?

It can be an ecological collapse, there can be big changes in geopolitics. On the one hand, if we don't stop climate change, the biophysical effects of climate will be very important. Famines, wars...If we don't stop, we're going to ruin. That's what most scientists say.

In short, what should we do to address climate change? What are the real solutions in the context in which we are?

A transition should be made, and this is my personal point of view, towards a material and energetic decline. And degrowth does not mean that economic growth needs to be lowered. It can continue to grow economically, but it does not have to be a materialistic growth, which needs energy and raw materials. That is the only realistic solution, in my view.

What role would the possible global organization to which reference has been made play in this transition?

On the one hand, the guarantee of doing things right. On the other hand, to propose ideas. One idea would be to introduce a CO2 tax, but at source, that is to say, to producers. This tax would reach the consumer who, first of all, would consume less. And you'd realize the distribution of the family budget ... The percentage of the energy budget, in the total of our families, is very small, should be much higher, taking into account the ecological and social benefit of energy production and consumption. The introduction of such a tax would reduce the consumption of energy-intensive products. That would be the first impulse of the transition. Of course, that single measure would not solve everything. But economically, it's the key.