Aviation contributes 3.5% to human-driven sources of climate change

Aviation has been calculated to contribute 3.5 per cent of all human activities that drive climate change, new research shows.

The findings of a new international study show that two-thirds of the impact from aviation is attributed to non-carbon dioxide emissions and the rest from CO2. The research was led by the UK’s Manchester Metropolitan University, in collaboration with numerous academic and research institutions across the globe, over the past five years.

Researchers evaluated all of the aviation industry’s contributing factors to climate change including carbon dioxide (CO2) and nitrogen oxide (NOx) emissions, and the effect of contrails and contrail cirrus – clouds of ice crystals created by aircraft jet engines at high altitude. This was analysed alongside the water vapour, soot, and aerosol and sulfate aerosol gases – fine particles suspended in the air – found in the exhaust plumes emitted by aircraft engines.

The study is unique because it is the complete first set of calculations for aviation that uses a new metric introduced in 2013 by the Intergovernmental Panel on Climate Change, explains a statement. This metric is called ‘effective radiative forcing’ (ERF) and represents the increase or decrease since pre-industrialisation times in the balance between the energy coming from the sun and the energy emitted from the earth, known as the earth-atmosphere radiation budget.

Using the new ERF metric, the team found that contrail cirrus’ impact is less than half than that estimated previously but still the sector’s largest contribution to global warming, by reflecting and trapping escaping heat from the atmosphere.

Carbon dioxide emissions represent the second largest contribution but unlike the effects of contrail cirrus, CO2’s effect on climate lasts for many centuries.

Lead author Professor David Lee said: “Given the dependence of aviation on burning fossil fuel, its significant CO2 and non-CO2 effects, and the projected fleet growth, it is vital to understand the scale of aviation’s impact on present day climate change, especially in view of the requirements of the Paris Agreement to reach ‘net zero’ CO2 emissions by around 2050.”

Approximately half the total cumulative emissions of CO2 were generated in the last 20 years alone, attributed largely to the expansion of the number of flights, number of routes and fleet sizes, particularly in Asia, though partially offset by improvements in aircraft and jet engine technology, larger average aircraft sizes and increasing efficiency in the use of aircraft capacity to fit more passengers in the same space.

Photo credit: Flickr Creative Commons

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