The team also used actual ground counts of penguins in their analysis. "The ground counts told us the density of penguin clusters, and we used this to multiply the area of penguins calculated by our satellite image analysis into penguin numbers," Fretwell told OurAmazingPlanet in an email.
The analysis not only doubled the previous estimate of emperor penguins, but also uncovered seven previously undiscovered colonies.
Fretwell said this kind of research is important, particularly in the face of a changing climate.
There are concerns that changes to Antarctica's ice heralds a difficult future for emperor penguins. The birds breed on the Antarctic sea ice during the brutal winter months, but earlier spring melts may pose threats to the more northern colonies, according to a statement from the British Antarctic Survey.
Areas of Antarctica have experienced dramatic changes in recent years; floating ice shelves have crumbled away and glaciers have sped their march to the sea. The Antarctic Peninsula is one of the fastest-warming places on Earth, with air temperatures rising between 4 and 4.5 degrees Fahrenheit (2.2 and 2.5 degrees Celsius) in the last 50 years.
Fretwell said the new technique provides at least one way to correlate any environmental changes with changes to emperor penguin numbers, and can be done year after year.
"This first study gives us the baseline from which to calculate any future trend in the population dynamics. It is much cheaper that Antarctic fieldwork, so it gives us a cost-effective, consistent, comprehensive snapshot of the population each year," Fretwell said.