It is written in a book

Examining the paper of old journals indicates climatic processes that took place in the last 150 years

Some of the historical information found in ancient volumes and yellowing journals may be hidden between the lines. Weizmann Institute of Science scientists discovered that these papers record the atmospheric conditions that prevailed while the paper was still part of a growing tree. By identifying different isotopes of carbon found in small pieces of paper taken from old newspapers, and analyzing the quantitative relationships between them, Prof. Dan Yakir from the Department of Environmental Sciences and Energy Research in the Faculty of Chemistry was able to track the increase in atmospheric pollution caused by the burning of fossil fuels, since the days of the Industrial Revolution.

Scientists usually reconstruct such historical atmospheric data from drilling into glaciers or tree rings. But according to Prof. Yakir, in order to get reliable results, a large number of trees must be tested. "Instead of walking around forests all over the world and sampling trees," he says, "we go to the public library." In the archives of the library at the Weizmann Institute of Science, for example, Prof. Yakir found old issues of scientific journals, whose age reaches up to over 100 years. He removed small samples from the margins of selected sheets, and took them for laboratory testing.

The laboratory test is based on testing the quantitative ratio between the relatively rare version of carbon (isotope 13C) and the amounts of common carbon (12C). This ratio provides information on the amount of carbon dioxide released into the atmosphere as a result of burning fossil fuels. The reason for this is that the plants, which absorb carbon dioxide from the air in the process of photosynthesis, prefer to use carbon dioxide that contains common carbon, which reacts faster than the heavy carbon. Thus, every summer - during which the level of photosynthesis reaches its peak - many tons of plant mass poor in the heavy isotope of carbon (C13) are created.

Millions of years ago such plant mass turned into oil, gas and coal - therefore these reservoirs are also low in the heavy carbon C13. The exploitation of coal and oil in these reservoirs since the industrial revolution releases back into the atmosphere this carbon, which is characterized by a small amount of the isotope C13, and as a result, the amount of this isotope in the atmosphere has been decreasing over the last 150 years. At the same time, many of the trees that absorb this carbon dioxide are cut down and turned into paper. Therefore, the paper found in the archives contains varying levels of the carbon isotope C13. Prof. Yakir showed that the process of continuous decrease in the levels of this isotope is clearly documented in the paper samples, and reflects the increased use of fossil fuels in the last 150 years.

The research has been going on for 14 years, during which, according to Prof. Yakir, he learned a lot about the paper industry. Some of the early sheets, for example, were printed on different paper in terms of the amounts of isotopes, and deviations in the data, which were also discovered during the Second World War, led Prof. Yakir to assume that it was recycled paper, or mixed with paper that is not made of wood (but, for example, of cotton or Pishta) - to overcome the shortage created during the war.

The levels of heavy carbon, C13, in the paper even revealed a number of local climatic phenomena, which are reflected, for example, in the differences between paper originating in America or Europe. "This method shows the potential of a wonderfully organized sample pool, which we have ignored so far," says Prof. Yakir. "Besides, it will be possible to use it to check the authenticity of ancient printed words."