The climate remains a mystery

5 June 2013

In his book Geschichte des Klimas (A history of the climate), one of the leading paleoclimate researcher takes us on a journey through the geological eras. Professor Dr. Frank Sirocko of the Institute of Geosciences at Johannes Gutenberg University Mainz (JGU) provides insight into the past while also venturing to forecast the future.

Frank Sirocko smiles while talking about something that has recently knocked his colleagues for a loop. "Strangely, there has been no increase in the temperature of the Earth's climate over the past decade and everything our predictions had forecast has not happened. This is really baffling. In the years 1980 to 2000, we always had these two curves that ran parallel to one another just as our models predicted. These showed that an increase in levels of carbon dioxide in the atmosphere was accompanied by global warming." Now all that is called into question ...

"Climate research is not like mathematics, where everything can be calculated using a specific formula," says Sirocko, professor at the Institute of Geosciences at Mainz University. "Climate research is more like a jigsaw puzzle. Once you've managed to put a few pieces together, a picture starts to emerge."

And some of these pieces are described in his recently published book. Geschichte des Klimas is the title of the rather slim volume. A few still shrink-wrapped copies are stacked in the professor's office. "I wrote this book with a broad audience in mind but it is also designed to serve as a text book for university students as well. The publisher first wanted me to write in a style suitable to that of German popular science magazines, but I refused. I wanted to ensure that it met certain academic standards."

Four global players are involved

Sirocko’s book takes its readers on a journey through the geological eras. "We will together be looking at the most important processes in the climate system," he writes in the foreword. "Join me on a journey through time and the changes to the global climate; we will be considering in detail those that have occurred in Central Europe. We will also be examining the correlations between climate change and human evolution and the way that humanity will continue to influence our climate."

For Sirocko, there are four major global players involved in determining the climate. Over the long term, the relative positions of the sun and Earth play an important role. The planet and the star are not always the same distance from one another. The resultant changes manifest themselves over cycles lasting 20,000, 40,000, and 100,000 years. Solar activity is a second factor: a larger number of sunspots means more solar flares, so that more energy reaches the Earth's atmosphere, particularly in the ultraviolet spectrum.

Then there are volcanic eruptions which have an influence as sudden events. And finally, there are greenhouse gases, predominantly carbon dioxide, and these were already a major climate determinant even before humanity appeared. Sirocko follows the interaction of these four factors over millions of years. He outlines what research can explain and also emphasizes where science is grasping at straws.

A lot has yet to be explained

For example, it is now an established fact that the Earth's temperature peaked 55 million years ago. The cyclical rhythms of warmer interglacial periods and ice ages have also been clearly identified. But when it comes to the retreat of the ice sheets at the end of the last ice age, things get problematic. Sirocko writes, "There are no genuinely dynamic ice models that are able to accurately reproduce the related complex physical processes with the necessary chronological timing."

It is his ability to admit that there are holes in the argumentation that gives the geoscientist so much credibility when he does present certain facts as certainties – irrespective of whether these relate to the past or future. One of these certainties is that humanity has long had a huge impact on its environment. "Over a period of at least 6,000 years, everything in Central Europe has been influenced by humankind." And, at the latest with the arrival of industrialization, humanity also began to have an effect on the atmosphere as well: 25 percent of the current level of the greenhouse gas carbon dioxide can be traced back to anthropogenic sources. The level of the less significant greenhouse gas, methane, has increased by 150 percent.

By now, most people start to ask themselves: How can researchers know about the climate in the past? Well, what they have done is create suitable archives of information. Core samples from the ice of the Antarctic, dust sediments, and tree rings provide the necessary data. Sirocko's Climate and Sediments work group at JGU has also set up such an archive. It is in the basement of the institute, where the geoscientist now invites us to join him.

Sources of fossil fuels are running out

The Eifel Laminated Sediment Archive (ELSA) consists of row upon row of core samples. They come from 22 maars located in the Eifel highland region of Germany and various aspects of them are currently being analyzed. "What we have here is a calendar that covers the last 500,000 years," explains Sirocko. The core samples would be 2,500 meters long if placed end to end.

But back to 2013, when humanity is still consuming the planet's fossil fuels at a breathtaking rate. Carbon dioxide that in the past of our planet was bound in the forms of petroleum, gas, and coal is now being released. "Carbon dioxide emissions will continue to increase over the next few years," predicts Sirocko. "One reason is that emerging nations are busy catching up when it comes to levels of industrialization."

And the release of greenhouse gases is not the only problem. The fossil fuels that power our modern world are beginning to run out. "I am convinced that in 15 to 20 years time, petroleum will no longer be available in the quantities we are used to, while coal will become scarce in 100 years time at the latest," states Sirocko. "We will then be forced, whether we like it or not, to fall back on solar energy."

The chance of carbon dioxide recycling

"I personally only see one solution: We need to recapture carbon dioxide from the atmosphere." This would be possible with the help of solar power. Sirocko believes that the southern European countries would be the perfect location for this. "Carbon dioxide could be converted to methane in thermal power plants there and this methane could then be transported to the north via pipelines and there it could be used as a fuel."

"This would represent an effective way of storing solar energy," says Sirocko confidently. A sustainable and self-contained carbon dioxide-methane cycle would make this form of energy generation viable. It also needs to happen before levels of carbon dioxide in the atmosphere become too high. "Nobody is yet working to develop the necessary technology, but the method is theoretically possible. And as soon as all the petroleum is used up, someone will try it. It would be nice if fundamental research were to start now."

But are greenhouse gases actually a problem? After all, it seems that the Earth has stopped warming up. Sirocko returns to the global players. "From 2007 at the latest, when Al Gore and the Intergovernmental Panel on Climate Change (IPCC) won the Nobel Prize, research has focused on carbon dioxide as the cause of climate change." The IPCC has received a huge amount of support while other factors that influence the climate have been neglected.

Sunspots are underestimated

"Forty years ago everybody was talking about sunspots. Many researchers at the time were convinced that changes in the sun were the most important factors controlling our climate," reminisces Sirocko. "The so-called Maunder Minimum, a phase lasting from 1650 to 1720 in which sunspots were relatively rare, was seen as proof of this hypothesis. Back then it was very cold." Scientists at NASA are now discussing whether the cold years since the most recent sunspot minimum in 2009 to 2011 might be associated with a similar process and could be masking the greenhouse effect that is still running in the background."

But it is difficult to finish a jigsaw puzzle when many pieces are still missing or misplaced. "What we thought correct 20 years ago may turn out to be completely mistaken today," Sirocko says thoughtfully as he leaves the basement filled with core samples. "It is important that we are willing to accept this."