Climatic Change Impacts On Astronomical Observations

Modern astronomical telescopes are powerful and astronauts are making them much more powerful. With telescopes like the Giant Magellan Telescope and the Extremely Large Telescope are seeing first light in the coming years, thus astronomical observing power will be greater than ever.

The lead researcher Faustine Cantalloube on the study said that “Climate change is affecting and will increasingly affect astronomical observations, particularly in terms of dome seeing, atmospheric water vapor content, surface-layer turbulence and the wind-driven halo effect in exoplanet direct imaging.” 

The study ‘The impact of climate change on astronomical observations’ was published in the current issue of Nature Astronomy and can be viewed online. Its results are not only important for astronomers to adapt their observations to changing environmental conditions, but it must also be taken into account when planning new large telescopes, such as the Extremely Large Telescope (ELT), which is currently being built near the Paranal.

Dr. Susanne Crewell and Christoph Böhm from the Institute of Geophysics and Meteorology were involved in the study. They had already explored various aspects of the past, present, and future climate at the telescope’s site in the framework of Collaborative Research Centre 1211 ‘Earth — Evolution at the Dry Limit’. The first author of the article is Faustine Cantalloube from the Max Planck Institute for Astronomy in Heidelberg.

The researchers investigated the extent to that climate change affects astronomy and specifically the standard of observations.  The team focused on the Paranal Observatory in northern Chile because it has a whole range of environmental sensors that document local meteorological conditions. These measurements yielded one of the most comprehensive data sets over the last three decades at a largely untouched location.

Image Source: Wikipedia

By using this data set, astronomers, atmosphere scientists, climate researchers, and meteorologists joined forces to identify important meteorological parameters that play a role in the quality of astronomical observations.  The data allowed them to analyze long-term trends over a period of more than thirty years to determine the impact of climate change on future observations. Using four examples, they showed how climate change is already affecting, or might affect the operation of an astronomical observatory in future. The VLT, operated by ESO, was served as an example.

Dr Susanne Crewell said that “The data showed a 1.5 ° C increase in near-ground temperature over the last four decades at the Paranal Observatory. This is slightly higher than the worldwide average of 1°C since the pre-industrial age.

Since the original telescope cooling system was not designed for such warm conditions, the quality of observations is increasingly endangered by more frequent turbulences and consequence of the rise in temperature. The expected rise of 4° C (the most pessimistic scenario of the ICCP climate simulations) within the next century thus has to be taken into account in the construction of the 39-metre Extremely Large Telescope (ELT) at a nearby site.

Particularly astronomers are facing the challenge of reduction in “dome seeing’, a reduction in resolution due to turbulence within the telescope dome. The researchers furthermore noticed an increase in turbulence in the air layer near the ground, making images blurred since cold and warm air layers with different refractive indices alternate more quickly. However, attributing this to climate change is difficult, since there were also constructional changes. The increase in wind shear in the upper troposphere in connection with the jet stream also leads to a so-called ‘wind-driven halo’. This phenomenon appears when atmospheric turbulence conditions vary faster than the telescope’s control system can correct them. This limits the contrast capabilities of the instrument and could potentially limit exoplanet studies. An increase in water vapour in the atmosphere moreover could lead to a reduction of the astronomical signal.

Image Source: arxiv

The above Driver Diagram is demonstrating how astronomers can embed climate change engagement in their professional work.

Sources: arxiv, Nature Astronomy, The University of Cologne

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