A new study has analyzed nearly 30 years of scientific data related to the melting of the Greenland Ice Sheet. The analysis points toward a possible global sea level rise of at least 10 cm by the end of the 21st century if global warming were to continue at the current trend.
The researchers warn that the estimates, which are largely in agreement with recent estimates reported by the Intergovernmental Panel on Climate Change, are “conservative” due to the strong impacts of changes in weather systems and potential ways in which ice loss is accelerated.
Led by Professor Edward Hanna from the University of Lincoln in the United Kingdom, an international research team, including climatologists and glaciologists from Switzerland, Denmark, Belgium, and the United States, performed the new study that evaluates the response of the Greenland Ice Sheet to climate change. The study outcomes have been reported in the International Journal of Climatology.
The Greenland Ice Sheet is a huge reservoir of ice containing water sufficient to eventually increase the global sea level by 7 m.
The team offers a fresh analysis of data related to the Greenland surface air temperature for the past 30 years until 2019, where the focus of the study was not only on coastal weather stations but also on the analysis of records from comparatively long-running sites on the inner plateau of the ice sheet.
The study identified that the Greenland coastal regions warmed considerably by around 4.4 °C in winter and 1.7 °C in summer from 1991 to 2019.
The study combined Greenland temperature data with the output of the computer model of ice-sheet mass balance for 1972 to 2018 and demonstrated that every 1 °C of summer warming leads to 116 billion tons of total mass loss and 91 billion tons of surface mass loss from the ice sheet annually.
Furthermore, the researchers employed certain newly available global and regional climate modeling tools to evaluate that, under the influence of sustained strong global warming (a “business as usual” scenario), Greenland could probably warm up to 4.0 °C–6.6 °C by the year 2100.
These latest and predicted future Greenland warmings are significantly higher compared to global temperature variations for corresponding time periods, which point toward a high sensitivity of the polar regions to climate change.
The researchers then used the relation they derived between the latest variations in Greenland summer temperature and surface mass balance to estimate a 10–12.5 cm increase in global sea-level rise by 2100, caused by increased Greenland surface mass loss and ice melt.
Prof. Hanna’s research group also examined the relationship between the changes in Greenland air temperature and a phenomenon known as atmospheric high-pressure blocking, which is caused by a higher-than-normal mass of air occasionally positioned over Greenland.
Although this relation has usually existed previously, it has gained more strength in summer and spring in recent decades. The researchers demonstrate that Greenland blocking played a vital role in the near-record Greenland melt in the summer of 2019 (narrowly exceeded by the all-time record in 2012) and indicate that potential future variations in blocking must be taken into account in computer-model projections of climate change.
The Greenland Ice Sheet is one of the most sensitive and reliable measures of global climate change. Here we have used relatively simple statistical analysis of data and model output from the last 30 years as a sense-check on prediction of future ice-sheet surface mass change.
Edward Hanna, Professor, Climate Science and Meteorology, School of Geography and Lincoln Centre for Water and Planetary Health, University of Lincoln
Hanna continued, “Our work, which represents in part a major updated analysis of Greenland climate records, is highly interdisciplinary since it cross-cuts between climate science and glaciology, and so will help improve interpretation of recent ice-sheet changes.”
The authors’ group very sadly observes the passing of their co-author Professor Konrad “Koni” Steffen from the Swiss Federal Institute for Forest Snow and Landscape Research WSL, who unfortunately died in an accident in Greenland on August 8th, 2020. Prof. Steffen was a trailblazer in Greenland Ice Sheet research and an esteemed, good, loyal, and inspiring collaborator over several years. The team misses him very much.
Hanna, E., et al. (2020) Greenland surface air temperature changes from 1981 to 2019 and implications for ice-sheet melt and mass-balance change. International Journal of Climatology. doi.org/10.1002/joc.6771.
Is there really life on Venus? How do we find out? – HalifaxToday.ca
Last week, an unlikely research project made a startling discovery: Phosphine gas in the atmosphere of Venus. That’s something that, as far as we know, is created by living organisms. Our efforts to find signs of life on other worlds, and a lot of our space dreaming in general, tend to focus on Mars. But all of a sudden we need to take a closer look at our other planetary neighbour.
So how can we find out if there’s really life right next door? What do we know about Venus and why has it been so hard to figure out so far? What else could possibly cause the presence of Phosphine and what would it mean, to space exploration and everything else, if this is really true?
GUEST: Neel Patel, space reporter, MIT Technology Review
The 'Red Planet' approaches – Coast Reporter
This summer has been pretty interesting with Comet NEOWISE, the Perseids and some close lunar/planetary appulses in September. (Yes, it’s my new vocabulary word of the month.) October, however, is all about Mars – but the COVID-19 threat we’re facing limits our options somewhat.
Opposition occurs when Earth passes between the sun and a celestial object – they’re opposite to each other in the sky. Because of our orbital periods – 365 days for Earth and 780 earth days for Mars – a Mars opposition happens about every 26 months. However, the accompanying composite of Hubble images from previous oppositions illustrates that there’s more to it than just that. For example, although opposition is Oct. 13, we’re actually slightly closer on Oct. 6.
First, neither planet has a circular orbit; Earth’s is slightly elliptical and Mars’ is much more so. Hence, the close approach distance varies according to how close or far from the Sun each planet is. Second, Earth and Mars orbit in slightly different planes; Mars can be above or below the plane of Earth’s orbit and therefore a bit further away. As well, Mercury and Venus slightly affect Earth’s orbit and Jupiter affects everything, so all the orbits change slowly over time. Finally, we’re in the northern hemisphere; a near-winter opposition puts Mars much higher in the sky at night and we look through much less atmosphere. Although Mars isn’t quite as close as it was in July 2018, it will be about 30 degrees higher – better seeing.
The Astronomy Picture of the Day site (APOD) at https://apod.nasa.gov/apod/ for Sept. 11 has a striking photo of Mars emerging from behind the Moon taken on Sept. 6 from Brazil, one of five occultations this year. The photo, lovely as it is, illustrates the problem of viewing Mars for most of us: you need a telescope. While you can see Jupiter as a small disc and four moons with good binoculars and a tripod, Mars at its best is only a third that size. Without the current pandemic, I’m sure the Sechelt observatory would be open to the public for this opposition and people could stare to their hearts’ content, but at this point it doesn’t look good. Any changes will be posted on the club website.
As in September, Jupiter and Saturn are low in the south after sunset, after their opposition in late July. The New Moon on the 16th coincides with its perigee (large tides) and it will pass Jupiter and Saturn a week later on the 22nd and 23rd. Interestingly, it will be a Full Moon on the 1st AND the 31st.
Remember, all of the movements of moon and planets described can be checked out on the web at: www.heavens-above.com. The next regular meeting of the Astronomy Club should be Oct. 9 at 7 p.m. using Zoom. Information on the speaker and topic and how to register for the meeting will be on the club website at https://sunshinecoastastronomy.wordpress.com/ the week of the meeting.
– Richard Corbet
Asteroid size of a bus comes close to Earth – Sierra Leone Times
Scientists at the U.S. space agency NASA say a small asteroid – roughly the size of a bus – passed close to Earth on Thursday, flying just 22,000 kilometers above the surface, within the orbit of geostationary satellites that ring the planet.
While the proximity to Earth might raise alarm, scientists at NASA’s Jet Propulsion Laboratory (JPL) in Southern California said even if the asteroid had entered the earth’s atmosphere, it almost certainly would have broken up and become a bright meteor.
The asteroid, known as 2020 SW, is about five to ten meters wide and was first discovered on September 18 by the NASA-funded Catalina Sky Survey in Arizona.
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NASA’s Center for Near-Earth Object Studies (CNEOS) — part of the JPL — then did follow-up observations and confirmed its orbital trajectory, ruling out any chance of impact.
CNEOS director Paul Chodas says an object this size, this close to earth, is not uncommon. He says, “In fact, asteroids of this size impact our atmosphere at an average rate of about once every year or two.”
After passing the Earth, the asteroid will continue its journey around the Sun, not returning to Earth’s vicinity until 2041, when NASA says it will make a much more distant flyby.
The space agency says they believe there are over 100 million small asteroids like 2020 SW, but they are hard to discover unless they get very close to Earth.
In 2005, Congress assigned NASA the goal of finding 90 percent of the near-Earth asteroids that are about 140 meters or larger in size. These larger asteroids pose a much greater threat if they were to impact, and they can be detected much farther away from Earth, because they’re simply much brighter than the small ones.
Chodas says NASA’s asteroid surveys are getting better all the time, and the agency now expects to find asteroids the size of 2020 SW a few days before they come near Earth.
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