More On Ice, Sea Levels, and Athropogenic Warming

Speaking of “OMG the ice is melting”, it is difficult to keep up with the flood (sorry) of data and analysis of the Earth’s ice and sea.

While I can glibly assert that the ice is melting and the seas are rising, the actual scientific picture is quite complicated. Let’s glance at some recent findings.

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From space, we can observe lots of things, including ice shelves and bergs. NASA released imagery from MODIS instrument on the Terra satellite which shows a large berg that broke off the Nansen Ice Shelf in Antarctica last week. This is the end of summer there, so the ice would have been melting for a few of months.

There is actually imagery from past years, in which we can see the ice grow and then break off over several years.

It is important to note that this “berging” is not necessarily evidence that the ice sheet is shrinking there. Ice sheets build up and berg off all the time. But it does show that we can watch developments closely, and in near real time.

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From space can also inventory seasonal ice coverage, which NASA has done since 1979. This year the “annual peak Arctic sea ice” was the smallest area since these data have been collected.  The data is from a Special Sensor Microwave/Imagers on defense satellites, which can map ice and water.

“The low sea ice maximum coincides with record high air temperatures in December, January, and February in the Arctic and around the planet.”

This shrinkage continues a steady trend since at least 1979. There is a nice animation here.

There seems little question that glaciers and sea ice are melting in many places, including Greenland and the Arctic. This meltwater will surely end up in the ocean, and sea levels will rise.

But what is driving this trend?

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An international team led by John A. Church and Ben Marzeion have presented a careful study based on computational simulations that consider several sources of climate change, including natural forces (e.g. fluctuations in solar influx), greenhouse gasses, and aerosols (e.g., dust and soot).[1]  Based on physical models, They use historical data to model the contribution of each of these factors. The resulting computed sea levels can be compared to actual measured levels.

Their conclusion is clear. Sea level rise was primarily driven by natural variation in the first years of the twentieth century. But around 1970, around 70% of sea level change was due to anthropogenic factors, primarily greenhouse gasses.

This conclusion is not especially surprising. The important thing, I think, is that their work is comprehensive and very careful. It is a really nice illustration of how to use computation and data to try to understand the Earth’s climate, uncertainty and all. Very nice work, and I’m sure it will be carefully evaluated and built on by other investigators.

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Together, these reports show the high quality, very careful study and hard work that goes into serious studies of the Earth’s climate, and the role that remote sensing plays.

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1. Aimee B. A. Slangen, John A. Church, Cecile Agosta, Xavier Fettweis, Ben Marzeion, and Kristin Richter, Anthropogenic forcing dominates global mean sea-level rise since 1970. Nature Clim. Change, advance online publication 04/11/online 2016. http://dx.doi.org/10.1038/nclimate2991

 

Space Saturday

OMG: Oceans Melting Greenland

One of the fascinating phenomena of the early twenty first, we are witnessing the rapid melting of the cryosphere, the glaciers and ice caps. My own view is that this process will be the geological marker for the Anthropocene, leaving an indelible mark on the planet in the form of many meters of sea level rise.

I’m pretty sure that the die is cast, there is no way to halt the process. But it is really cool to be able to watch it happen in our lifetime.

For one thing, it’s not clear exactly how all the variables work together, and feed back on each other. Warmer air melts ice, but may change precipitation patterns. Iceless water and rock warms quicker, melting more ice. Melted ice water flows into the ocean, possibly changing currents and cooling or warming sea ice. There is plenty of work for scientists.

One project is the not-at-all-subtly-named “OMG – Oceans Melting Greenland” from NASA JPL. Using remote and in situ sensing, the project examining the interactions of glaciers, the ocean, and the geometry of the continental shelf.

The Greenland ice sheet is about the area of Texas, and is a mile deep. If and when the ice melts completely, it is enough water to raise sea levels by 6 meters. (Odds are that you, my friend, are under water when it gets over 2 meters higher.)

“That massive ice sheet touches the sea along more than 44,000 kilometers (27,000 miles) of jagged coastline. Hundreds of fjords, inlets, and bays bring ocean water right to the edge of the ice and, in some places, under it. This means the ice sheet is not just melting from warm air temperatures above; it is also likely being melted from water below.”

NASA Earth Observatory map by Joshua Stevens, using Oceans Melting Greenland (OMG) data courtesy of Josh Willis/JPL. Photograph by Josh Willis. Caption compiled by Mike Carlowicz from reporting by Patrick Lynch and Carol Rasmussen, NASA Earth Science Communications.

The NASA mission is using aircraft to collect high precision maps of the extent and height of the ice over a number of years, ships to map the sea floor, and floating instruments to record temperature and salinity of the ocean at various depths. Together, this data will help model the complex interactions, and perhaps understand how fast the ice will melt.

 

Space Saturday

 

Review of “The Human Age” by Diane Ackerman

The Human Age by Diane Ackerman

I’ve written before about the Ahthropocene and the current mass extinction event, as well as “re-wilding“.

The Anthropocene, “The Human Age”, is the geological age of humans: it will be easily visible in the geological and fossil record of the Earth.

There is little doubt that we have and continue to transform the planet in ways so huge that they deserve a designation such as Anthropocene. There is still disagreement over what a good boundary for the transition from Pleistocene to Antrhopocene, and whether we are already in the new age or soon will be.

(These boundaries are often somewhat arbitrary, for the start of a geological “age”do we mean to mark the beginning of the changes or a point where the changes predominate or some point of “new normal”? My own position is that we are in the end-days of the Pleistocene—humans are the apex species of the old age—and the new will begin when and if the Antarctic ice cap melts. At that point, the Pleistocene will be drowned under many meters of ocean rise. No problem at all using that as a geological marker!)

Dianne Ackerman takes as given that we are in “The Human Age”—as does anyone who observes the Earth today. She is a long time “nature writer”, who has written for many years about “nature” and “human nature”. In this book she examines the end of “nature”, the place of humans, all the ways that humans can remake “nature”, what “human” is becoming as we change even our own “nature”.

In this book she wonders if, in this “Human Age” is “Nature” “Natural”, and what does “natural” mean. If “natural” once meant the absence of and opposite of “human”, then nature is long gone on this planet. She is a clear-eyed critic, with no unrealistic notions that we can go back, and a glass-half-full hope that we can do better going forward.

Ackerman is a beautiful writer, and lavishes clever but not too portentous prose to describe the nature that she so clearly loves. This is the best part of the book, by far.

Two examples of phrases that caught me. Describing a large magnolia tree, she tells us that it which offers “leafy pounce-ways for squirrels” p. 111. She describes the awesome technology of bioprinting replacement organs as “hope’s calligraphy” p. 246)

This book touches upon many topics, with much of the book is written in short, often first person, reportorial pieces glued together to make a larger point. Many of the best snips come from observations in her own yard, and visits to her local University (Cornell). Others report brief visits to far flung sites (seed vaults in the Arctic, zoos, “green” tech sites, and so on), backed with research.

I found quite a few cool things to look up, and some of the things I already know about. Much of section IV is about “being here now” in our digital age, a topic of great interest to me. She treats us to a far more poetic argument than I could give, for instance, comparing viewing Icebergs online to actually being there. Images may have virtues, but they cannot portray the “grandeur of size, sounds, colors, waves, and panorama.” (p. 141)

She discusses animal computer interfaces, which I have been thinking about for quite a while (e.g., see [2]).  There is so much more that she apparently did not dig into—perhaps she might glance at the citations in my paper for some future ideas.

Everything hinges on the writing, which seeks to tie all these little pieces into a sort of coherent story. At its best, the writing is wonderful (e.g., descriptions of her own yard and other natural scenes) In other places, the snippets are shallow and poorly informed, and sometimes disconnected from the whole. For example, she waxes eloquently about the promise of EWICON (bladeless wind energy), which is purely imaginary technology. And she is excited by computers sending messages to report the “happiness” of plants, which she conflates with real plant signals (which are too subtle and slow for humans to notice)—pure nonsense, and worse, a misunderstanding of the truly cool aspects of both those topics. Since I know something about these topics, it was painful to read her misguided, if poetic, renditions.

Overall, the good stuff outweighs the errors, and the poetic language makes me wish I could write so purty.

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1. Ackerman, Diane, The Human Age: The World Shaped By Us, New York, W. W. Norton & Company, 2014.
2. McGrath, Robert E., Species-appropriate computer mediated interaction, in Proceedings of the 27th international conference extended abstracts on Human factors in computing systems. 2009, ACM: Boston, MA, USA.