Showing posts with label albedo. Show all posts
Showing posts with label albedo. Show all posts

Tuesday, October 27, 2020

A vicious circle. Global heating leads to melting ice leads to more heating.....

                                            Nature Communications

A polar bear navigates a dwindling ice pack. Photo by Andreas Weith

The melting of ice in polar and mountain regions around the world could lead to an additional 0.43 °C increase in global warming in the long term, according to a study published online in Nature Communications.

The loss of ice cover is known to influence air temperatures, for example through albedo changes (the amount of sunlight reflected from the Earth’s surface). Although the mechanisms that are responsible for increased warming are well understood, it isn't clear how large the contributions of different ice sheets and feedback mechanisms to global temperature changes are.

Nico Wunderling and colleagues use a simplified Earth system model in combination with different CO2 concentration levels to provide such an estimate. They find an additional median warming of 0.43°C in response to the loss of all ice sheets at CO2 concentrations similar to today's (400 parts per million). The contributions from different ice masses range from 0.05°C for the West Antarctic Ice Sheet to 0.19°C due to the loss of Arctic summer sea ice. 

However, these experiments do not consider changes in CO2 concentrations over time or feedback mechanisms that could have an impact on shorter time-scales. Furthermore, the authors note that this warming does not emerge over years or decades, but rather on a time-scale of centuries to millennia (although they highlight that the Arctic might become ice-free during the summer within the 21st century). Therefore, these results should be interpreted as idealized estimates of contributions of different ice sources and feedback mechanisms.

The Arctic may be sea-ice-free in summer by the 2030s

  Nature Communications                                                 Photo by Patrick Kelley   The Arctic could be sea-ice-free during th...