Professor Nir Shaviv: Global Warming Mostly Caused By Sun, Not Humans

Astrophysicist Nir Shaviv says IPCC has got it wrong as they attribute global warming to anthropogenic greenhouse gas emissions and leave out solar effects.

“There's no such thing as a scientific consensus,” Nir Shaviv, a professor at the Racah Institute of Physics at the Hebrew University of Jerusalem, says in response to a question about what he thinks of the widespread claim that there is a scientific consensus on the anthropogenic nature of climate change. “In science, we deal with open questions and I think that the question of climate change is an open question. There are a lot of things which many scientists are still arguing about,” he explains.

Indeed, there are scientists who say that climate change is caused entirely by humans and the situation is very dire. But then there are those who say that although humans are causing much of the warming, the situation is not as bad as we are being told by politicians and activists through the media. Some think that CO2 plays an important part in the current warming trend and some believe its role is insignificant.

Although Shaviv assesses that some of the warming in the 20th century is indeed the result of increasing atmospheric CO2 concentrations, then most of the change is a natural phenomenon. “My research has led me to strongly believe that based on all the evidence that's accumulated over the past around 25 years, a large part of the warming is actually not because of humans, but because of the solar effect,” he says.

Up to two-thirds of the warming comes from the sun

As an astrophysicist, Shaviv's research has largely focused on understanding how solar activity and the Earth's climate are linked. In fact, he says, at least half, and possibly two-thirds, of the 20th century's warming is related to increased solar activity. Shaviv has also shown that cosmic rays and their activity influence cloud cover formation also causing the climate to change. They have been working on this issue together with Danish astrophysicist Dr Henrik Svensmark.

Professor Shaviv says that possibly two-thirds of the 20th century's warming is related to increased solar activity. Photo: Alex Braga/Unsplash.

In any case, Shaviv says, if solar activity and cosmic ray effects are taken into account, the climate sensitivity remains relatively low, or simply put - an increase in the proportion of CO2 in the atmosphere cannot cause much warming. It has long been attempted to calculate how much a doubling of atmospheric CO2 can raise the temperature of the Earth. The first attempt was made more than 100 years ago by the Swedish chemist Svante Arrhenius, who suggested an answer of up to 6 degrees. Since then, this number has been revised downwards, but not enough, according to Shaviv. “If you open the IPCC (Intergovernmental Panel on Climate Change – ed) reports, then the canonical range is anywhere between one and a half or two, depending on which report you look at, to maybe four and a half degree increase for CO2 doubling. What I find, is that climate sensitivity is somewhere between one and one and a half degree increase per CO2 doubling,” Shaviv says, adding that he does not expect the temperature rise in the 21st century to be very high.

Explaining the warming that has happened primarily with CO2 is where the IPCC's scientific reports err, Shvaviv says, by failing to account for the solar effect. And because they do not account for it, but there is still a need to explain the temperature rise, the rise in CO2 levels in the atmosphere, which has been attributed to human influences, has been used to explain it. Shaviv explains that this is the wrong answer as it fails to take into account all the contributing actors.

Is the planet boiling?

But is this temperature rise causing a climate crisis? Shaviv's answer to the question is simple and clear: "No." He explains that the average temperature on the planet has risen by one degree Celsius since about 1900, but this is not unprecedented. We are familiar, for example, with the Medieval Warm Period, when the Vikings charted the coast of Greenland, including its northern part, which today is covered with ice even in summer. “This kind of climate variation has always happened. Some of the warming now is anthropogenic, but it's not a crisis in the sense that the temperature is going to increase by five degrees in a century and we're all doomed. We just have to adapt to changes. Some of them are natural and some are not, but they're not large,” Shaviv explains.

It has been widely reported that both 2023 and 2024 were the warmest years on record. Referring to this rise in temperatures, UN Secretary-General António Guterres already in July 2023 declared that we have entered an ‘era of global boiling’. Shaviv says that of course, we can have average surface temperatures that are highest if we only look back 100 or 150 years. “If you go back a thousand years it was just as warm. If you go back 5 000 years it was definitely warmer. So, It doesn't mean much,” he explains.

And if you look at a longer time scale, warmer periods have alternated with colder periods throughout. Also, over the last 100,000 years, the Earth has been in an ice age for most of that time, and the retreat of the ice in Europe and North America happened about 12,000 years ago.

Do extreme weather events prove a climate crisis?

However, it is often claimed in the media that we are in an unprecedented and critical climatic situation and all the reported extreme weather events are said to be proving it.

In reality, there is no indication that most extreme weather events are more frequent or in any way more severe than in the past. Take hurricanes, for example. It's true that the damage they cause has increased over time, but Shaviv says that's because more people live near the coast. “If you look at the statistics of hurricanes making landfall in the US, which is a relatively reliable record, then you see that there is no significant change,” he says. Shaviv adds that, in reality, there is not even any reason to expect a warming climate to bring more hurricanes. “Sure, you need hotter waters to generate hurricanes, but you also need the gradient, you need the temperature difference between the equator and the subtropics in order to drive the hurricanes. And warmer Earth actually has a smaller temperature difference. So it's not even clear ab initio whether you're going to have more hurricanes or less,” Shaviv explains.

There is no climate crisis and the trend of extreme weather events is not going up. Photo: Nikolett Emmert/Unsplash.

Large wildfires, for example, are also associated with climate warming, but Shaviv says there is no reason for this either. “In the US in the 1930ies the annual amount of area which was burnt a year was way larger than what it is today,” he says, adding that the reality is that a large proportion of fires are caused by poor forest management, which fails to clear the forest floor of flammable material.

Towards nuclear energy

In the light of the above, climate change does not make it necessary to abandon fossil fuels. However, Shaviv says we should still move towards cleaner energy. Firstly, burning fossil fuels causes real environmental pollution - in particular coal, which is still on the rise worldwide. Secondly, fossil fuels will run out one day.

But mankind cannot replace these fuels with wind and solar power. “First of all, it's very expensive. You can see that any country that has a lot of any of those, they pay much more for electricity,” Shaviv says. He suggests looking at electricity prices in countries such as Germany or Denmark, where wind and solar have been developed with billions of euros of government aid, and comparing them with, for example, France which uses nuclear power. What makes this form of energy so expensive is its intermittent nature - generation takes place when the sun shines and the wind blows. So to guarantee electricity supply, either huge storage capacity or backup systems, such as gas-fired power stations, are needed.

Professor Shaviv believes that in the future, much more reliance should be placed on nuclear power. Photo: Wikimedia Commons.

Shaviv believes that in the future, much more reliance should be placed on nuclear power, which does not have the pollution problems of fossil fuels and, unlike wind and solar, can provide a stable energy supply. However, the critics of this plan remind us of past nuclear accidents - Chornobyl in Ukraine, Three Mile Island in the USA, and Fukushima in Japan. Each of these accidents had its own causes - in the case of Chornobyl and Three Mile Island, technical defects mixed with human error, and in the case of Fukushima, natural forces, in other words, the earthquake and tsunami. In the case of Fukushima in 2011, however, no one died as a direct result of the accident at the nuclear power plant, but thousands of people died as a result of the tsunami that devastated the coastline.

Shaviv says there is no point in comparing the safety of nuclear plants that have suffered accidents in the past with today's technology. “I don't think it's going to be a problem in the sense that we can have an extremely safe design,” he says, adding that the wider deployment of nuclear power will happen whether the West does or not. “If you look at China, which is energy-hungry, they don't care about public opinion as much as we do in the West. And they don't have as much problem with regulation. So they're just going to run forward and instead of building or opening a coal power plant every few weeks, in a few years, they’re going to be opening a nuclear power plant every few weeks,” Shaviv says. He adds that the West would also be wise to participate in this development, rather than moving in the opposite direction.