You know how in the world's hottest, sunniest countries people wear long white or light-colored clothes, like the thawb (robes) of the Arabian peninsula or the khaki suits of the British in India? That's because lighter colors reflect sunlight, while dark colors absorb them. So you'll keep cooler in white clothes when you are outside.
Now imagine the Arctic — do you picture a swath of white, perhaps slowly melting glaciers, snow and ice-covered seas? Just like light-colored clothes, all that white snow and ice reflects lots of solar energy back, keeping temps cooler. That reflected light is albedo.
When glaciers melt completely, they leave the darker blue oceans or brown earth behind, which absorb solar energy and hold it in, leading to warmer temps over a longer period of time. As the earth warms, it will accelerate heat-absorbtion, leading to ever-higher temperatures. It's a feedback loop that many scientists have trouble predicting the effects of: Once it gets rolling it could have significant or disastrous climate-change effects.
Recently, algae has been thrown into the mix. Yes, as strange as it might sound, these tiny plants could be exacerbating global warming. Scientists have found that a red-colored algae blooming on glaciers and ice reduces albedo and — as darker colors will — leads to more warmth on the already-melting ice.
A team led by Stefanie Lutz and Liane G. Benning at the German Research Centre for Geosciences and at the University of Leeds, respectively, took 40 samples from 21 glaciers in the European Arctic. They were looking at the diversity of the algae at the sites which ranged from Greenland to north of Sweden.
According to the study published in the journal Nature Communications:
"We estimated that the overall decrease in snow albedo by red pigmented snow algal blooms over the course of one melt season can be 13 percent. This will invariably result in higher melt rates. We argue that such a ‘bio-albedo’ effect has to be considered in climate models."
Some scientists think the record melting occurring on ice sheets in Greenland and other places in the world is caused by this "bio-albedo" effect of the algae.