SPIEGEL: You make concrete statements on how much human activity contributes to climatic events and how much of a role natural factors play. Why don't you publish your prognoses in a professional journal?
Vahrenholt: Because I don't engage in my own climate research. Besides, I don't have a supercomputer in my basement. For the most part, my co-author, geologist Sebastian Lüning, and I merely summarize what scientists have published in professional journals -- just as the IPCC does. The book is also a platform for scientists who apply good arguments in diverging from the views of the IPCC. The established climate models have failed across the board because they cannot cogently explain the absence of warming.
SPIEGEL: You claim that the standstill has to do with the sun. What makes you so sure?
Vahrenholt: In terms of the climate, we have seen a cyclical up and down for the last 7,000 years, long before man began emitting CO2 into the atmosphere. There has been a warming phase every 1,000 years, including the Roman, the Medieval and the current warm periods. All of these warm periods consistently coincided with strong solar activity. In addition to this large fluctuation in activity, there is also a 210-year and an 87-year natural cycle of the sun. Ignoring these would be a serious mistake …
SPIEGEL: … but solar researchers are still in disagreement over whether the cycles you mention actually exist. What do you think this means for the future?
Vahrenholt: In the second half of the 20th century, the sun was more active than it had been in more than 2,000 years. This "large solar maximum," as astronomers call it, has contributed at least as much to global warming as the greenhouse gas CO2. But the sun has been getting weaker since 2005, and it will continue to do so in the next few decades. Consequently, we can only expect cooling from the sun for now.
SPIEGEL: It is undisputed that fluctuations in solar activity can influence the climate. Most experts assume that an unusually long solar minimum, evidenced by the very small number of sunspots at the time, led to the "Little Ice Age" that began in 1645. There were many severe winters at the time, with rivers freezing over. However, astrophysicists still don't know the extent to which solar fluctuations actually affect temperatures.
Vahrenholt: Many scientists assume that the temperature changes by more than 1 degree Celsius for the 1,000-year cycle and by up to 0.7 degrees Celsius for the smaller cycles. Climatologists should be putting a far greater effort into finding ways to more accurately determine the effects of the sun on climate. For the IPCC and the politicians it influences, CO2 is practically the only factor. The importance of the sun for the climate is systematically underestimated, and the importance of CO2 is systematically overestimated. As a result, all climate predictions are based on the wrong underlying facts.
SPIEGEL: But you are doing exactly what you criticize climatologists of doing: Using a thin body of data, you make exact predictions. In your book, you estimate the sun's influence on the climate down to the last 0.1 degrees. No one can do that.
Vahrenholt: I don't claim that I know precisely whether the sun is responsible for a 40, 50 or 60 percent share of global warming. But it's nonsense for the IPCC to claim that the sun has nothing to do with it.
SPIEGEL: On balance, you predict a global cooling of 0.2 to 0.3 degrees Celsius by 2035. Why such a risky prediction?
Vahrenholt: If you want to revitalize the deadlocked debate, you have to have the courage to name a number. And we derive this number from scientific studies on climate history to date.
My favourite area of science/technology (thorium reactors, LENR, "hydrogen economy", asteroid mining, hyperloop, "smart" power, "X is the cause of disease Y", ...) is ignored/neglected/suppressed by the establishment for evil political reasons which I can only hint at. If only scientists would research it better and gubmints would fund a Manhattan-style project, all would be cogently explained and proven. I would do it myself, but I am not a scientist and I do not have a supercomputer in my basement.