Dáil Éireann Debate, Thursday - 3 April 2014
155. Deputy Pádraig Mac Lochlainn asked the Minister for the Environment, Community and Local Government if his Department has made any inquiries or conducted any research into the alleged polluting effects of chemtrails or contrails from aircraft. [15872/14]
View answer'Chemtrails' are not a scientifically recognised phenomena and my Department has not conducted any research on them.
With regard to visible condensation trails, or contrails as they are often known, left by jet aircraft, my Department has previously been informed by Met Éireann that these trails are formed through the emission of exhaust gases from jet engines of aircraft in the upper troposphere. The main component of these gases is water vapour. Ambient air temperature at jet cruising altitudes is often below -500 C. Under these conditions, water vapour cools and condenses and the particles act as ice nuclei, leading to the production of ice crystals; these ice crystals are what are visible from the ground as a linear cloud of condensation.
Depending upon atmospheric conditions, contrails can rapidly dissipate or remain for some time, gradually spreading horizontally into an extensive thin cirrus cloud layer. Water in the atmosphere commonly evaporates to become water vapour. As a general rule, the drier the air the more effective this evaporation process will be. Under more humid conditions, there will be less effective evaporation and so contrails will generally last longer in more humid air. Contrail formation is also influenced by wind speeds, with higher winds disrupting and breaking up contrail formation.
Contrails do not adversely impact ambient air quality in Ireland. Met Éireann advises that there is some evidence that contrails can influence climatology but they have little impact on day-to-day weather. The purported reason for the former is that the contrails (or consequent cirrus cloud) will trap outgoing long-wave radiation, thus leading to warming in the atmosphere, and that this effect is greater than the reflection of short-wave radiation from the sun.
The Environmental Protection Agency (EPA), is currently funding a PhD study on contrails and their potential effect on climate as part of its STRIVE research programme. The study titled 'Cloud cover and radiation balance changes over Ireland due to aircraft induced contrails' is due to be completed later this year.
