People have become a cause of climate change long before the industrial revolution and the era of fossil fuels. A new study shows that the remnants of the earliest carbon emissions due to human activities are still present in the atmosphere.
Scientists say carbon emissions from pre-industrial era, due to deforestation due to population growth, are responsible for 9 percent of the warming observed at this time on the planet.
"The earlier releases occurred, the less they affect the current climate. But the emissions remain in the atmosphere for a long time, from hundreds of years to millennia, "- explains the researcher Julia Pongratz of the Max Planck Institute for Metrology in Germany.
This rethinking of carbon can reduce the relative degree of fault assigned to various nations, as much as 2 percent, the researchers note. The political implications are not yet clear, but most of the international climate change negotiations are based on the principle of "the polluter pays", where the most active producers of carbon take greater responsibility for the mitigation of global warming. Given the events that happened back in the ninth century, a slightly larger load will be on China and the South Asian nation.
Julia Pongratz and her Californian colleagues noted that the contribution of different countries to increase the level of carbon dioxide in the atmosphere based on emissions data since 1840. But in the period between about 800 and 1850 AD, the world population has increased fivefold and exceeded one billion. With a jump of size has increased the need for agricultural development and, accordingly, in deforestation.
Scientists call trees carbon sinks. They pull carbon dioxide from the atmosphere and store it. When trees are cut, they not only stop absorbing carbon dioxide during photosynthesis reaction, but are beginning to rot and emit greenhouse gas preserves.
Using historical records, scientists have created a virtual map of land use, dating back in time to the year 800. Such data can be combined with computer climate models to determine how changes in land use affect climate.
Using these models, the researchers found that 5 percent of the excess CO2 in the atmosphere — emissions, which would not have been without influence people — date back to pre-industrial era to 1850. Percentage of pre-industrial emissions is different for individual regions. For example, China and South Asia have only recently started to burn fossil fuels, but in the course of the history of these regions experienced significant deforestation. Since pre-industrial emissions of these countries ranges from 10 to 40 percent of the total carbon footprint.
Today, as scientists have found, most of the carbon emissions associated with deforestation occurs in tropical regions of the world.
Who is to blame?
Since the late 1800s, the planet warmed by about 0.74 degrees Celsius. About 9 percent of the warming due to the pre-industrial emissions, the researchers note in their report.
"This is a pure scientific research, and many aspects related to the question" Who is responsible for this? ", Which is beyond the scope of science — said Julia Pongratz. — But if we start the modern climate of the regions of the world, a picture that takes into account these pre-industrial emissions, does look different. "
As previously reported by Pongratz and her colleagues, this historical look at the carbon emissions reveals some of the most significant events that shaped the history of the people. In particular, after the Mongol invasion of Asia carbon emissions in the region have fallen, because during the war and the fall of the population gave forests to recover. Black Plague in the 1300s, as it turned out, was also the reason for the reduction of carbon emissions, but not such a significant, as the Mongol invasion.
The team notes that her study is not associated with contemporary political events and gives a very interesting opportunity to see how the situation developed over time with global warming.