Interviewed here in Der Spiegel:
"Today, I want new scientific findings to be included in the climate debate. It would then become clear that the simple equation that CO2 and other man-made greenhouse gases are almost exclusively responsible for climate change is unsustainable. It hasn't gotten any warmer on this planet in almost 14 years, despite continued increases in CO2 emissions. Established climate science has to come up with an answer to that. ...
"The long version of the IPCC report does mention natural causes of climate change, like the sun and oscillating ocean currents. But they no longer appear in the summary for politicians. They were simply edited out. To this day, many decision-makers don't know that new studies have seriously questioned the dominance of CO2. CO2 alone will never cause a warming of more than 2 degrees Celsius (3.6 degrees Fahrenheit) by the end of the century. Only with the help of supposed amplification effects, especially water vapor, do the computers arrive at a drastic temperature increase. I say that global warming will remain below two degrees by the end of the century. This is an eminently political message, but it's also good news. ...
"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 …
"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. ...
"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. ...
"[T]he declining solar activity, as well as the fluctuations in ocean currents, such as the 60-year Pacific oscillation, which was in a positive warm phase from 1977 to 2000 and, since 2000, has led to cooling as a result of its decline. Their contribution to the change in temperature has also been wrongly attributed to CO2. Most of all, however, the last sunspot cycle was weaker than the one before it. This is why the sun's magnetic field has continued to weaken since 2000. As a result, this magnetic field doesn't shield us against cosmic radiation quite as well, which in turn leads to stronger cloud formation and, therefore, cooling. What else has to happen before the IPCC at least mentions these relationships in its reports? ...
"In addition to carbon dioxide, we also have black soot, for example. It creates 55 percent of the warming effect of CO2, but it could be filtered out with little effort within a few years, especially in emerging and developing countries. And, in doing so, we would achieve huge benefits for human health. ...
"All I'm saying is that CO2 is a climate gas, but that its effect is only half as strong as the IPCC claims. ..."
