Luminous ‘mother-of-pearl’ clouds explain why climate models miss so much Arctic and Antarctic warming

Katrin Meissner, UNSW Sydney; Deepashree Dutta, University of Cambridge, and Martin Jucker, UNSW Sydney Our planet has warmed by about 1.2°C since 1850. But this warming is not uniform. Warming at the poles, especially the Arctic, has been three to four times faster than the rest of the globe. It’s a phenomenon known as “polar amplification”. Climate models simulate this effect, but when tested against the past 40 years of warming, these models fall short. The situation is even worse when it comes to modelling past climates with very high levels of greenhouse gases. This is a problem because these are the same models used to project into the future and forecast how the climate will change. They are likely to underestimate what will happen later this century, including risks such as ice sheet melting or permafrost thawing. In our new research published today in Nature Geoscience we used a high-resolution model of the atmosphere that includes the stratosphere. We found a special type of cloud appears over polar regions when greenhouse gas concentrations are very high. The role of this type of cloud has been overlooked so far. This is one of the reasons why our models are too cold at the poles. Polar Stratospheric Clouds over Norway (Night Lights Films - Adrien Mauduit) Back to the future Looking...

Read More........→November 08, 2023

Polar bears may struggle to produce milk for their cubs as climate change melts sea ice

During their time onshore, polar bear mothers may risk their survival by continuing to nurse when food is not available. (Shutterstock) Louise Archer, University of TorontoWhen sea ice melts, polar bears must move onto land for several months without access to food. This fasting period is challenging for all bears, but particularly for polar bear mothers who are nursing cubs. Our research, published in Marine Ecology Progress Series, found that polar bear lactation is negatively affected by increased time spent on land when sea ice melts. Impaired lactation has likely played a role in the recent decline of several polar bear populations. This research also indicates how polar bear families might be impacted in the future by continued sea-ice loss caused by climate warming. Challenges of rearing cubs While sea ice might appear as a vast and perhaps vacant ecosystem, the frozen Arctic waters provide an essential platform for polar bears to hunt energy-rich seals — the bread and butter of their diet. Sea ice is a dynamic environment that can vary through time and in different regions of the Arctic. Polar bears in Canada’s western Hudson Bay area experience seasonal sea ice, which melts in the warmer summer months, forcing the polar bears to move onto land until cooler winter temperatures cause the sea ice to refreeze.While...

Read More........→October 09, 2023

We are poised to pass 1.5℃ of global warming – world leaders offer 4 ways to manage this dangerous time

Marcus E Jones, Shutterstock Jonathan Symons, Macquarie UniversityFor three decades, the goal of international climate negotiations has been to avoid “dangerous” warming above 1.5℃. With warming to date standing at around 1.2℃, we haven’t quite reached the zone we labelled dangerous and pledged to avoid.But recent scientific assessments suggest we’re on the brink of passing that milestone. Within this decade, global annual temperatures will likely exceed 1.5°C above the pre-industrial average for at least one year. This threshold was already briefly passed for the month of July 2023 during the Northern summer. The question is, how do we manage this period of “overshoot” and bring temperatures back down? The goal will be to restore a more habitable climate, as fast as possible. Today an independent group of global leaders released a major report. The Climate Overshoot Commission offers guidance at this crucial time. So far the report’s call for an immediate moratorium on “solar radiation management” (deflecting the sun’s rays to reduce warming) has attracted the most attention. But the details of other recommendations deserve closer inspection.  How can we respond to climate overshoot? Historically, climate policies have focused on mitigation (reducing greenhouse gas emissions). More recently, adaptation has gained...

Read More........→September 18, 2023

How is Antarctica melting, exactly? Crucial details are beginning to come into focus

Madelaine Gamble Rosevear, University of Tasmania; Ben Galton-Fenzi; Bishakhdatta Gayen, The University of Melbourne, and Catherine Vreugdenhil, The University of MelbourneThe size of the Antarctic ice sheet can be hard to comprehend. Two kilometres thick on average and covering nearly twice the area of Australia, the ice sheet holds enough freshwater to raise global sea levels by 58 metres. Ice loss from this sheet is projected to be the leading driver of sea level rise by 2100, yet its contribution remains highly uncertain. While sea levels are certain to rise this century, projections of the contribution from Antarctic ice vary from a 44 cm rise to a 22 cm fall. Much of this uncertainty is because the ocean processes that control the fate of the sheet occur on an incredibly small scale and are very difficult to measure and model. But recently scientists have made significant progress in understanding this “ice-ocean boundary layer”. This progress is the subject of our new review paper, published today in Annual Reviews. Shrinking, thinning and retreating At the margins of the Antarctic ice sheet, glaciers flow into the Southern Ocean, forming floating ice shelves. These ice shelves act as keystones, stabilising the ice sheet. They’re also shrinking. The ocean melts ice shelves from below – a process known as “basal melting”....

Read More........→June 14, 2023

Why are sunsets so pretty in winter? There’s a simple explanation

Chloe Wilkins, University of NewcastleIf you live in the southern hemisphere and have been stopped in your tracks by a recent sunset, you may have noticed they seem more vibrant lately. The colours are brighter and bolder, and they linger longer in the sky. Why are sunsets “better” at some times of the year compared to others? We can use science to explain this. There are many ingredients for a “good” sunset, but the main three are clear skies, low humidity, and the Sun sitting low in the sky. From light to colour To understand why we get such vibrant sunsets in the colder months of the year, we first need to know how colours appear in the sky. All visible light is actually energy that travels in waves; the length of those waves determines the colour that our eyes see. Although sunlight might look white to us, it’s actually a mix of different wavelengths of light that make up all the visible colours – from fiery reds and oranges (longer wavelengths) to deep blues and purples (shorter wavelengths). These individual colours become visible when sunlight is “scattered”, which is precisely what happens when it passes through the invisible gas molecules in Earth’s atmosphere – mostly nitrogen and oxygen. When sunlight hits these molecules, it’s absorbed and shot back out (scattered) in different directions. Blue and violet light...

Read More........→June 01, 2023