Global warming is even affecting astronomy, new study says

Astronomy may be the last sphere one would expect to be affected by global warming. But now researchers say even large ground-based optical observatories are suffering from the cumulative effects of higher atmospheric temperatures.

A paper to appear in the journal Astronomical Society of the Pacific (PASP) Publications notes that long-term atmospheric warming causes a slight decrease in the number of visible light photons that penetrate Earth’s atmosphere from any given celestial target.

The known rate of temperature increase due to global warming is in the same sense and about the right size as the increase in atmospheric “attenuation” seen in these data, Eric Steinbring, lead author of the paper and an astronomer at Herzberg Astronomy and Astrophysics Research Center, he told me.

More “attenuation” simply means that fewer photons from stars and galaxies can make it through Earth’s atmosphere, where they can be picked up by ground-based optical telescopes, Steinbring says. The team specifically focused on earlier observations in the visible spectrum at 0.6 microns, he says. They concluded that because of this warming, about 0.2 percent fewer photons per decade make it through the Earth’s atmosphere and surface.

In calculating their models, the team used two decades of archival data from the 8-meter optical telescopes at the Gemini North and South observatories in Hawaii and Chile. About 250,000 observational samples taken over a 17-year period were used to infer long-term changes in atmospheric attenuation, the authors note.

The team also used measurements of incoming solar radiation from the summit of Mauna Loa dating back to 1958. They then compared this data with data from the Gaia object catalog that expires in 2021. It was then combined with archival records of the sky and meteorological conditions. same time period.

Even over the past two decades, the loss in the (combined) fraction of photons that “get through” appears to be close to one percent, Steinbring says. If it’s true for Gemini, it should be true for other comparable ground observatory sites, he says.

The authors note that global warming will lead to more water vapor in the atmosphere which can lead to more moisture and more cloud cover and precipitation such as rain, sleet or snow. One result may be more nighttime telescope dome closures due to bad weather, the authors write. And in locations around the world, worse observational conditions are predicted by climate change modeling, the team writes.

As for the duration of this deterioration in astronomical vision?

Mauna Loa solar data date back to 1958, Steinbring says. When stripping out the effects of three major volcanic eruptions — with global effects lasting years — as well as a few smaller eruptions, he says, there appears to be a smooth observation over that time period. If we limit this data to after 2000, when the Gemini North Observatory first launched, he says, then that decline looks even steeper.

How will this affect future large ground observatories?

Photon loss in this wavelength regime is proportional to the aperture of the telescope, Steinbring says. Over time, he says, the phenomenon will “move away” into the telescope’s active aperture by about 12 centimeters a year. In other words, this will essentially cause a given telescope’s sensitivity and light-gathering ability to decrease over time.

What kind of observations will be most affected?

Any observation depends on very precise photometry. That is, the variations in brightness in stars and other celestial objects, Steinbring says. For example, this would have an impact on high-precision wide-field optical surveys that look for transient events — brief, isolated flashes from distant sources, he says.

The bottom line;

“The effect of global atmospheric change appears to be detectable in the images themselves,” Steinbring said. “And once you see something in your data, you can no longer ignore it.”