Sad polar bear In every article about climate change, it’s pretty much guaranteed you’ll see a picture of a sad polar bear balancing on a small piece of floating ice….see right for ours. Climate research clearly proves that polar ice (including glaciers, pack-ice and glaciers) are melting. Also, the sea level is rising and snow cover is decreasing…but why is this all happening? The science behind melting ice caps. So Elsa managed to unfreeze her icy home town…but this isn’t exactly the case in the poles. All the finger-pointing comes back to yet again greenhouse gases and how they trap heat from the sun in the Earth’s atmosphere. Check out our article on climate change for the low down on how this works. It all comes down to something called ‘albedo’. No, it’s not a fancy Italian cheese, it’s the fraction of solar energy (which is short-wave) that’s reflected from the Earth back into space. Essentially, it’s how ‘reflective’ the Earth’s surface is. Some surfaces are more reflective than others – paler surfaces have a high albedo and will reflect light, whereas something darker has a low albedo and will absorb heat more. This is why black tarmac roads get really hot in the summer (as you’d know if you attempt to go barefoot in Summer). Snow has a very high albedo so it reflects approximately 95% of sunlight (so its albedo is 0.95). Water reflects less sunlight – about 10% (its albedo is 0.10). Hence, the less a surface reflects the sun’s radiation, the more it absorbs and is therefore easily heated-up. Arctic Sea Ice melt contributes to climate change by reducing the Earth’s overall reflectivity Great…so how does this fit into climate change? As temperatures rise with global warming, more ice (high albedo) is melted into water (low albedo). So there’s more water to heat-up, which in-turn, melts more ice…and so on. This is a positive feedback climate process. As more and more ice melts, so the sea level rises causing flooding and loss of habitat for animal life which live on the polar ice, such as Arctic fox and polar bears. Polar ice sheets are melting approximately 9% each decade, and could have ice-free in summers by the end of the century. The largest single block of ice in the Arctic (the Ward Hunt Ice Shelf) has been around for about 3000 years and began cracking in 2000 – within two years, it’s completely split in two and is breaking apart. Albedo Positive Feedback Loop It’s not just the poles who are at risk because of albedo. Urban environments such as cities experience something called the ‘urban heat island effect’. Highly developed areas tend to have less vegetation and more infrastructure with darker surfaces (asphalt roads, buildings, etc.) which absorb and trap heat, especially during the summer months. This causes problems as people in cities are at a greater risk for heat-related illnesses. The good news is that we can use albedo to our advantage- by building paler buildings and planting more vegetation with a higher albedo to reflect heat back into space.
