“Climate science is not normal science,” Danish astrophysicist Dr Henrik Svensmark says. “It’s a bad career move to go against the idea that CO₂ is the only driver of climate change,” he notes. In other words, to say that important causes of climate change might lie elsewhere means losing your research funding. For many scientists, this would mean the end of their scientific career, as without funding, it is impossible to conduct research. “There’s so much politics involved in it even in academia. There is a sort of self-censorship.”.

Pressure from climate activist circles against scientists who dare to approach the issue scientifically can sometimes even get physical. Svensmark recalls a conference in Germany at which he gave a presentation that required police protection, since demonstrators wanted to storm into the conference hall.

On another occasion, glue was poured into the door locks of the conference building to prevent participants from entering, and graffiti was sprayed on the building, saying it was a Nazi gathering. “There’s nothing rational about such actions, and it is difficult to have a meaningful discussion. You also hear people saying that the science has been done. Now it’s only climate action that is needed,” Svensmark says, noting that such statements are nothing but propaganda.

Sun instead of CO₂

Professor Svensmark has spent his long scientific career studying the effects of the Sun and cosmic radiation on the Earth’s climate. He is a former head of the Sun-Climate Research Centre at the Danish National Space Centre. He currently holds a senior researcher position at the Technical University of Denmark’s Department of Space Research and Technology.

Svensmark says that CO₂ is a greenhouse gas, and there is no doubt about it affecting the temperature. However, he says that this effect is relatively benign – probably about one degree for every doubling of CO₂ in the atmosphere.

One degree is not a very big change, considering that we know from the Earth’s long history that there have been truly dramatic climate fluctuations. There have been periods when ice covered the planet all the way to the equator, and there have been periods when there was practically no continental ice and the air temperature was perhaps even 10 degrees higher than today. “If we look at geological timescales, we have had enormous changes in climate. And of course, all of this is completely natural. And the question is, why did we have such big climate changes? My work can explain why we have such large climate changes,” Svensmark says. The idea is that energetic particles born in the aftermath of exploding stars, called cosmic rays, can affect Earth’s cloud cover. Regulating clouds will impact Earth’s energy balance and, thereby, climate.