Are you having a laugh?!

According to research carried out by A. R. Ravishankara and colleagues at NOAA (National Oceanic & Atmospheric Administration) Nitrous Oxide N2O (commonly known as laughing gas) is the "single most important ozone-depleting emission".

This statement is surprising considering N2O is not restricted by the Montreal Protocol and is therefore freely emitted at an estimated rate of 10.5million metric tons per year according to the IPCC.

N2O is produced by human activity in large scales as a by product in the use of fertiliser in agriculture and fossil fuel combustion. N2O is known to catalytically destroy ozone via a similar process to that of chlorine examined in a previous blog. Interestingly chlorine and nitrous oxide have a dampening effect each other's ozone depleting potential (ODP) by interfering with the chemical processes involved. This point is key to the understanding of the results provided by the study.

ODP allows for the comparison of the amount of stratospheric ozone depletion caused by the emission of a unit mass at the earth's surface to that caused by the release of CFC-11. For example, according to the World Health Organisation CFC-12 has an ODP of  1.03, therefore slightly more damaging to ozone than CFC-11

A 2D model used to calculate ODP showed that the (pre CFCs) 1959 ODP of N2O was at 0.026, compared to a year 2000 level of 0.017. This demonstrates a marked decrease due to the influx of CFCs into the stratosphere between the above years. By restricting CFCs through the Montreal Protocol the amount of chlorine in the stratosphere gradually reduces which in turn allows for an enhancement in N2O ozone depletion and it is therefore suggested that the ODP of N2O will increase to similar levels of 1959 (0.026), which is a 50% increase in ODP.

To compound this effect is that N2O is a potent greenhouse gas, in fact it has a global warming potential 300 times stronger than that of CO2. Although it is produced is smaller quantities than CO2 this two pronged effect on climate that N2O exhibits is hard to ignore. The graphs to the left demonstrate, using data from various studies and the models referenced by A. R.Ravishankara, that N2O (red) has a projected potential to reach almost 30% ODP of the total CFCs exhibited in the 1980s. The graph below that is Global Warming Potential (GWP) for 100 years, and this also shows the potential increase that unrestricted N2O emissions can have upon the earth's heat budget.



So what does the future hold for N2O?

Will N2O have the last laugh...?

Listen to this podcast, featuring an interview with A.R. Ravishankara to find out more.