One of the key strands of the EGU so far this year has been discussion of the proposed new geological time period known as the Anthropocene. This concept was first proposed by the ecologist Eugene Stoemer in the 1980’s, with Nobel Prize Winner and atmospheric chemist Paul Crutzen bringing renewed attention to the term in the early 21st Century. It refers to the concept that the impact of humans on our environment is worthy of its own epoch.
I attended the EGU press conference ‘Are we living in the Anthropocene?’ on Tuesday, where atmospheric chemist John Burrows presented work on how air pollution is a clear fingerprint of human influence on the atmosphere, with subsequent impacts on our environment. You can see a couple of written summaries of them here and also a podcast by the Barometer, which I featured on here.
He illustrated this with several global maps of air pollutants such as nitrogen dioxide and aerosol particles. Nitrogen dioxide is mainly emitted by human activities, particularly vehicles. Fires are another significant source via human activities. I’ve included an example below from a paper on measuring NO2 from space, which showed a weekly cycle in the amount of NO2 in the atmosphere. Major population centres are easily identifiable as red colours in the plot below, while concentrations reach a minimum over marine areas. NO2 has direct health consequences when breathed in and is part of the cocktail of emissions that can go on to produce tiny aerosol particles.
Nitrogen dioxide (NO2) from the Global Ozone Monitoring Experiment (GOME) on board the ESA-satellite ERS-2. Red colours are major NO2 emission sources.
Source: S. Beirle et al., 2003, Atmospheric Chemistry & Physics (available open access here).
Another illustration is of deforestation and agricultural fires in South America. Such fires occur every year, with a distinct seasonal cycle which peaks in the ‘dry’ season. The plots show monthly averaged aerosol optical depth measured by the MODIS instrument on NASA’s TERRA satellite. This is a measure of the amount of aerosol in a vertical column through the atmosphere.
Aerosol optical depth over South America during the fire season from 2010-2012. Source: NASA’s TERRA mission via the Giovanni Data and Information Services Centre.
The smoke builds up over large areas of the continent and has potentially significant implications for climate, weather, human health and ecosystem development. There is also a large degree of variation from year-to-year, with the peak in 2010 being due to a substantial drought in the Amazon. Such conditions provoke more burning as it is tough to burn rainforests when it is raining! Furthermore, the lack of rain means that removal of the smoke from the atmosphere is reduced, so the smoke can form a dense layer of pollution. The burning is often more intense also as the forest environment is more susceptible to fire.
Biomass burning occurs on particularly large scales across South America, Africa and Indonesia and reflects a considerable environmental and atmospheric fingerprint by human activity. Deforestation has drastically changed the face of the Amazon Rainforest over the past 40 years, which I’ve written about previously here.
Atmospheric sleuthing
Air pollution provides a clear, distinct and global signature of human influence on our atmosphere and is known to have significant implications for our environment. This fingerprint is just one of many that has potentially led us into the Anthropocene. Identifying the issues is just one part of problem; tackling them is quite another.
