Our studio guest is Prof. Wolfgang Sachs, who heads the Berlin office of the Wuppertal Institute for Climate, Environment and EnergyDW-TV: Saving energy by about eighty percent sounds really great but don’t we really improve just on a bad system, a system which will never truly become sustainable? Wolfgang Sachs: Well, that is certainly a danger if we go to the extreme because, after all, it is not very rational to run highly efficiently into the wrong direction. But having said that of course it makes a lot of sense taking the example of the truck to improve the efficiency of particular devices, of machines and of cars and trucks as well.   DW-TV: But it could actually hinder investments in the right technologies, the ones not using fossil resources. Wolfgang Sachs: Well, I'm not so sure because even if you think of, you know, the solar future, there is no doubt whatsoever that we cannot have a solar future at the present level of energy consumption. So, the first imperative is to bring down the overall energy need and that's what the truck example shows. DW-TV: Overall energy need has actually gone up in the last years even though all of our devices, our fridges, our applications have become more efficient in the past. How come? Wolfgang Sachs: Very right so. I mean, the most outstanding example in a certain way is the car. I mean, we know that the specific efficiency of a car, which means the efficiency of a single car, the fuel efficiency, has increased over the last twenty years. But the problem is not solved. Why? Because we have put more cars on the road, the cars have become heavier and speedier so the growth effect has eaten up the efficiency effect. DW-TV: How do we solve that? Wolfgang Sachs: That shows that specific efficiency is not enough. You have to look at the entire system, you have to discuss how many cars, how heavy cars are, what kind of speed they offer, so the performance level has got to be kept on an interm...