Featured Science Paper
The importance of geomagnetic field changes versus rising CO2 levels for long-term change in the upper atmosphere
Scientists found that changes in the Earth’s magnetic field are more relevant for climatic changes in the upper atmosphere (about 100-500km above the surface) than previously thought. Understanding the cause of long-term change in this area helps scientists to predict what will happen in the future. This has key implications for life back on earth.
A good understanding of the long-term behaviour of the upper atmosphere is essential; it affects a lot of satellite-based technology, such as global navigation systems and high-frequency radio communication systems. Some satellites even operate within the upper atmosphere itself. The increase in atmospheric CO2 concentration has been thought to be the main cause of climatic changes at these high altitudes. This study suggests that magnetic field changes that have taken place over the past century are as important.
Both increasing levels of CO2 and changes in the Earth’s magnetic field affect the upper atmosphere, including its charged portion, also known as the ionosphere. This paper used computer simulations to compare the effects of these two factors over the past century. While CO2 causes heat to be trapped in the lower atmosphere, it actually cools the upper atmosphere. The simulations show that the increase in CO2 concentration over the past 100 years has caused the upper atmosphere, at around 300km altitude, to cool by around 8ºC. At the same altitude, changes in the Earth’s magnetic field caused a similar amount of cooling over parts of North America, but caused a warming over other parts of the world, with the strongest warming, of up to 12ºC, located over Antarctica.
The new simulations also indicate that rising CO2 levels have caused the densest part of the ionosphere to lower by about 5km globally. Changes in the Earth’s magnetic field can cause much larger changes, but they are very dependent on location and can be either positive or negative; over the southern Atlantic Ocean a decrease in height of up to 50km was found, while an increase in height of up to 20km was found over western Africa.