Climate change impacts astronomical observations

Date:
September 17, 2020
Source:
University of Cologne
Summary:
Already, climate change is having an impact on the conditions
of space observation at the Very Large Telescope in the Atacama
Desert. In future, new telescopes will have to be adapted to the
expected changes, a new study.



FULL STORY ========================================================================== Climate changes associated with global warming can affect astronomical observations. That is the result of a study involving scientists from
the University of Cologne. The international research team investigated
a range of climate parameters at the Very Large Telescope (VLT) at the
Paranal in the Atacama Desert in Chile, where the European Southern
Observatory (ESO) operates its telescopes. Among other things, the
team evaluated the data for temperature, wind speed and wind direction,
and the water vapour content in the atmosphere over a period of several decades. This revealed an increase in temperatures above the world average
and also increasing image blur due to air turbulence -- so-called seeing.


==========================================================================
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 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.

The Cologne-based scientists Professor Dr Susanne Crewell and Christoph
Bo"hm from the Institute of Geophysics and Meteorology were involved
in the study. In the past, 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 which climate change affects astronomy and in particular the quality 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.

Based on this data set, astronomers, climate researchers, atmosphere scientists, and meteorologists joined forces to identify important meteorological parameters that play a role in the quality of astronomical observations. The data allowed them to analyse 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.

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

Since the original telescope cooling system was not designed for such warm conditions, the quality of observations is increasingly endangered by more frequent turbulences -- a consequence of the rise in temperature. The
expected rise of 4DEG 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.

In particular, astronomers face the challenge of a reduction in the
so-called '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.

Through their unique perspective on the universe, astronomers know
that the origin of life on Earth was a complex process made possible
only by the coincidence of extremely rare circumstances. There is no
second Earth in our neighbourhood. For this reason, the current issue
of Nature Astronomy, published on September 10, is dedicated to the
topic climate. The special issue aims to raise awareness in astronomy
for climate aspects that are important for the work of astronomers.


========================================================================== Story Source: Materials provided by University_of_Cologne. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Faustine Cantalloube, Julien Milli, Christoph Bo"hm, Susanne
Crewell,
Julio Navarrete, Kira Rehfeld, Marc Sarazin, Anna Sommani. The
impact of climate change on astronomical observations. Nature
Astronomy, 2020; 4 (9): 826 DOI: 10.1038/s41550-020-1203-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200917105324.htm

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