Sunday, May 18, 2014

Antarctic Ice Shelf update

For a long time, the Antarctic has been a bit of an anomaly for climate scientists. While the arctic sea ice cover has changed dramatically in recent times, with new sea lanes opening, and entire ecosystems being threatened, Antarctic sea ice has not seemed to change that much. 

One factoid that climate change skeptics often cite is that the Antarctic sea ice is even gaining ice cover. While the oceanic sea ice in Antarctic is occasionally gaining ice, the situation for land ice is much less secure, and recent research is revealing new insights into the situation in Antarctica.
Map of Antarctica

Anarctica is divided into an east and west section, which can be seen on the image above. The grey in this map represents large ice shelfs, which are over open ocean (making them sea ice.)  As most who are interested in climate change know, this sea ice does not directly contribute to sea level rise, because they are already displacing water. The real problem comes from the ice that is over land. Unlike in Greenland, the Antarctic topography is a gradual slope from the Tans-antarctic Mountains to the ocean. Without sea ice acting as a barrier, the mainland glaciers can potentially "slide" into the ocean, in perhaps a very dramatic fashion. 

It is with this background information that recent evidence becomes particularly sobering.  according to this article:

a NASA study concludes that the melting of the West Antarctic Ice Sheet (WAIS) has "past the point of no return." This now unstoppable state of retreat will lead to a rise in oceans of 10-13 feet. To put this into the perspective, the remnants of Miami will be an island chain with most of the city submerged. It turns out the culprit for this retreat is not so much the warmer air, but a warmer ocean. The warmer ocean is melting the glaciers from below, and "lubricating" them as the slide into the ocean. In another study, models showed these glaciers experiencing a "rapid collapse" between 200 and 1,000 years in the future.

This is bad news, but not particularly shocking. The WAIS is know for it's rapid movements and potential instability, but the East Anatarctic Ice shelf, which was believed to be much more stable may be in for some trouble as well. 
according to this article
"we show here that the removal of a specific coastal ice volume equivalent to less than 80 mm of global sea-level rise at the margin of the Wilkes Basin destabilizes the regional ice flow and leads to a self-sustained discharge of the entire basin and a global sea-level rise of 3–4 m"
While this study shows we have some time before this collapse finishes (5-10k years) it will still add 10-13 feet to sea level rise even if the climate stops warming. Taken together these data points show that we are committed to at least to a 20-25 foot sea level rise in the future. The only question now is the time frame for this rise and if we will adapt to it.

In terms of climate science, the Antarctic ice sheets represent some of the largest wildcards in the field. Even with a linear decline, they pose problems to future civilizations, but with possibilities of rapid collapses and sheer volume of water stored in them, they represent a more immediate threat to ourselves, and our children than many of the other "known unknowns" in climate science.

Friday, January 17, 2014

IPCC AR5 Working Group II Summary for Policymakers

The IPCC is well known for their tendency to leak documents before their final release, and the working group 2 of the AR5 is no exception. The summary for policymakers for the WG II deals primarily with the impacts, adaptations, and vulnerabilities of climate change, and here are some of the moreinteresting highlights of the summary:

  • Transformative changes may be necessary as a response to projected climate changes: 

This might not sound like that big of a statement, until you read the IPCC’s definition for “transformation,”which is :
“A change in the fundamental attributes of a system, often based on altered paradigmsgoals, or values. Transformations can occur in technological or biological systems, financial structures, and regulatory, legislative, or administrative regimes.”
The IPCC report is acknowledging the possibility that sustainability might be impossible without a paradigm shift in our current global culture.

  • Some ecosystems and human systems show "significant vulnerability" to climate variability: 

This is one point the IPCC is making with "very high confidence." This vulnerability is exacerbated in developing countries.

  • Several major terrestrial ecosystems are undergoing broad-scale changes that can be characterized as early warnings for coming regime shifts, in part due to climate change:

One of the most inimical changes we expect from climate change is shifts in ecosystems. While some areas of northern latitude might shift from unproductive land to farm land, many regime shifts could be less welcome. Imagine Oklahoma drying up and becoming a permanent desert or the Amazon  Rainforest becoming a prairie. Many of these changes would release more carbon into the atmosphere, which could accelerate the warming already occurring.    

  • Effects of climate change on food production are evident in several regions:

Much like the regime shifts, so far the negative effects of climate change on food production have been more negative than positive. This means that a future earth will have decreased food productivity as billions of people are added to the global population.

  • Terrestrial and freshwater ecosystems can, when pushed by climate change, cross “tipping points” and abruptly change in composition, structure, and function. The crossing of these tipping points will result in significant increases in carbon emissions to the atmosphere
The idea of a tipping point makes the previous two predictions that much more ominous. The idea of non-linearity and “tipping points” means rapid changes which could happen at anytime and in the blink of an eye

  • Key risks of associated with global mean temperature increase >4o C relative to preindustrial include exceedance of human physiological limits in some locations and nonlinear earth system responses: 
The 4o mark is shaping up to be a key determinant of the fate of humanity in a future earth. This threat is made that much more ominous with recent reports that indicate this temperature range is more probable than the lower end estimates.

  • Animals and plants are adapting to climate change:
Unlike some humans in the United States, the larger biosphere is reacting to an actively changing climate. Animals and plants are changing their ranges and their abundance. While the evidence is still inconclusive, there is some indication that recent extinctions are attributable to this changing climate.

This is just some of the many new revelations in the report. This is perhaps the strongest position the IPCC has taken when addressing the severity of climate change and its potential impacts on the future of the world.