Sub-bullet b: Antarctica

Sub-bullet b: "A clear warming trend is evidenced by the Antartctic ice sheets"
Hierarchy: Part II:1:A:iv:b

Back to Intro - Back to Outline - Up to Bullet iv - Back to Sub-bullet a - Forward to Sub-bullet c

Introduction:
Antarctica, like Greenland, has a complex climate and thus the logical structure of Sub-bullet a will be followed. Simply, this means that we will use current understanding of how warming could effect the ice in Antarctica and data showing the trends of the distribution of that ice to conclude whether warming is occurring. The issue of causality will be left at this point unless evidence can be found which attributes the observed behavior to effects other than warming.

The bulk of the ice on Antarctica consists of two main sheets: the East Antarctic Ice Sheet [EAIS] and the West Antarctic Ice Sheet [WAIS]. The EAIS is much higher in elevation and therefore colder and less susceptible to warming than the lower WAIS. Below is a map compiled by NASA's ICESat showing the altitude of the upper surface of the Antarctic ice sheet.
This uneven distribution of ice mass and altitude will be critical for understanding the behavior of the Antarctic ice sheet.


In most respects Antarctica is as different from Greenland as two polar ice sheets can possibly be. In contrast with Greenland, Antarctica is naturally very cold; a large majority of the surface area of the continent averages below freezing year-round. Since Anatarctica is less marginal for ice than Greenland, a small rise in temperature isn't likely to be the difference between ice and liquid water except at the extreme edges. This means that melting is relatively less important in Antarctica as a factor for mass loss. The interior is large and very cold and in this region scientists expect that a warming climate would increase the ice mass since precipitation would increase--perhaps even enough to make the total mass balance increase due to warming. The Antarctic peninsula sticks much farther north and thus is more susceptible to warming trends than the coasts. Antarctica also does not rely on an exterior ocean current to cool it, and contains over 10 times the ice that Greenland does. All of these factors make Antarctica theoretically much less sensitive to small climate effects as Greenland is.


Despite all of these differences, we are looking for the same warming signature for Antarctica as we were for Greenland: positive mass balance in the interior, potentially negative and accelerating mass balance at the edges [since thinning is not just related to melting but to ice dynamics like glacier flow], and glacial dynamics features like accelerating flow. A refinement of the mass balance model predicts that the WAIS will see mass loss and the EAIS will see mass gain; this is the signature we are looking for.
[Refer to bullet iv for further introductory material]

Study 1 : GRACE weighs in on mass balance
Measurements of Time-Variable Gravity Show Mass loss in Antarctica
Isabella Velicogna and John Wahr, Science 311, 1754 (2006)



Antarctic mass rates from GRACE
J. L. Chen et al., GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L11502

Interannual variations of the mass balance of the Antarctica and Greenland ice sheets from GRACE
G. Ramillien et al., Global and Planetary Change 53:3, 198-208 (2006)

Simple: The researchers who conducted two of the three of our GRACE studies for the Greenland mass balance trend also conducted similar studies for Antarctica, and another group worked on the data as well. Their conclusions are the same: interior mass is increasing, peripheral mass is decreasing, with a net decrease in mass that is quickly accelerating. See Sub-bullet a: Greenland for more GRACE discussion.

Details: All three studies found large negative mass balances in the WAIS and mass gain or balance in the EAIS. A figure from Velicogna and Wahr illustrates this [the green line is the EAIS trend and the red line is the WAIS trend]:


Mass balance findings for these three studies are summarized in the table below.

All three studies also corrected the data for post-glacial rebound--the upward swelling of the crust resulting from the loss of glacial period ice--which yields more accurate but less precise data, since the post-glacial rebound is poorly known. Chen et al. describes the limit of knowledge [units, parenthetical statement and emphasis mine]:


"The calculations here show that the estimates of Antarctic snow/ice mass rates from GRACE data are completely dependent on the adopted PGR [post-glacial rebound] model, with uncertainties that might be on the order of 100% Our estimate of -99 or -77 cubic kilometers per year mass loss in West Antarctica is consistent with that of Velicogna and Wahr of -148 cubic kilometers per year, given the large PGR uncertainty and that here we only compute the mass loss of the Amundsen Sea Embayment in West Antarctica."

The take-home message is that we shouldn't have much faith in the exact numerical values of the mass balance, but that the trend of mass loss in the WAIS and mass gain in the EAIS is clear.


Discussion: The two studies with the most comprehensive geographical scope [Velicogna and Wahr and Remillien et al. ] agree within quoted error limits. The total mass balance isn't the first clue to a warming climate that Antarctica offers anyway [although it's the driving global factor in sea-level change, which has the potential for enormous effects]. What is important is also what is clear from the data: Antarctica is undeniably showing the signs of warming--decreasing ice mass in the WAIS and increasing or stable ice mass in the EAIS.

Conclusion: The GRACE data constitute strong evidence of a south polar warming trend.

Study 2: Sattelite radar altimetry measures mass balance
Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992–2002
H. Jay Zwally et al., Journal of Glaciology, Vol. 51, No. 175, 2005

Not-yet-published sattelite radar altimetry Antarctic mass balance study
Eric Rignot

Simple: The European remote sensing sattelites ERS-1 and -2 used radar altimetry to measure the altitude of ice in the Antarctic ice sheets. The first study is comprised of data from 1992-2002 which shows a mass loss in the WAIS and a mass gain in the EAIS which contributed to an overall negative mass balance. Additionally, the as-yet-unpublished second study--another by Eric Rignot--apparently fuses newer ERS-1 and -2 data with similar data from Japanese and Canadian sattelites and finds that ice loss in the WAIS increased extremely sharply during the decade 1996-2006.

Details: Covering a time period prior to most of the studies we've seen so far, the first ERS data is crucial in establishing a longer-term trend. This analysis is the most sophisticated to come out of the ERS program; the authors attempt to correct for some small but important factors which most other studies ignore, having to do with the dynamics of ice compaction. The dH/dt [rate of change of ice sheet altitude] map below represents the corrected data from Zwally et al.:


Rignot's technique is different than Zwally's; Rignot measures the amount of ice leaving the continent indirectly, by monitoring the flow of ice off the continent in glaciers. The benefit of this method is that it allows the researchers to ignore the problems that Zwally had to design sophisticated corrections for, such as the sensitivity of compactibility of new ice to temperature. Additionally, Rignot combined many different large datasets and has data up to 2006, greatly enhancing the completeness and relevancy of the data.

Quote from article on Rignot's upcoming paper: "The team found that the net loss of ice mass from Antarctica increased from 112 (plus or minus 91) gigatonnes a year in 1996 to 196 (plus or minus 92) gigatonnes a year in 2006."

Zwally et al. Quote: "The ice sheet inWest Antarctica (WA) is losing mass (–47 +/- 4Gt per year) and the ice sheet in East Antarctica (EA) shows a small mass gain (+16 +/- 11 Gt per year) for a combined net change of –31
+/- 12 Gt per year (+0.08mma–1 SLE). "

Discussion: The data from this study solidly confirms the existence of the bimodial east/west mass gain/loss signature in Antarctica; the signature of warming. Furthermore, Rignot's study--which used data from the same sources and identical analysis--found solid evidence that the ice mass loss in Antarctica is accelerating at a phenomenal pace; a solid sign of warming. Two more sattelite radar altimetry studies, Wingham et al. and Davis and Li found a slight mass increase. However, both of these studies found it difficult to analyze the peripheral regions and thus left them out of the analysis altogether. Since a majority of the loss we see occurs at the periphery, these studies do nothing but confirm the other studies' findings of a mass increase in the interior.
[Zwally et al. study also analyzed the Greenland ice sheet and found a small positive mass balance, which is not inconsistent with the studies reported in the Greenland section for this time period]

Conclusion: The ERS data constitutes evidence of a south polar warming trend.

Study 3: Laser altimetry analyzes glacial dynamics
Accelerated sea-level rise from West Antarctica
Thomas, Rignot, et al., Science 8 October 2004:Vol. 306. no. 5694, pp. 255 - 258

Simple: Using laser altimetry data from sattelites and aircraft, Thomas et al. have measured the discharge from the glaciers in a section of the WAIS. They discovered a steeply accelerating flow from the 1990's until 2003; a glacier dynamics marker indicative of warming.

Details: Thomas et al. found that 60% more ice was flowing out of the catchment basin feeding the Amundsen sea in west Antarctica than was accumulating due to precipitation. They collected precise ice thickness data from aircraft flown from Chile and compared it with various sattelite data sets to create a map of ice thinning rates for the catchment area. A quote: "The catchment regions of Amundsen Sea glaciers contain enough ice to raise sea level by 1.3 m. Our measurements show them collectively to be 60% out of balance, sufficient to raise sea level by 0.24 mm/year. Although these glaciers are the fastest in Antarctica, they are likely to flow considerably faster once the ice shelves are removed and glacier retreat proceeds into the deeper part of glacier basins."

Discussion: Not only does this large imbalance of outflow/inflow point to conditions now being different than they were previously, but the study reports an acceleration of the imbalance, which signifies compounding factors in recent years. Even more impressive is the potential for yet higher rates of mass loss when/if the ice shelves melt, effectively pulling the rug out from under the glaciers.

Conclusion: This glacial dynamics study constitutes strong evidence of south polar warming.

Other studies
Recent sea-level contributions of the Antarctic and Greenland ice sheets
Andrew Shepherd and Duncan Wingham, Science 315, 1529 (2007)

Simple: This is a review of mass-balance data. It does a much better job than I can, and it reviews most of the same data I have.

Mass balance of polar ice sheets
Eric Rignot and Robert H. Thomas

Simple: Another review but older. Same conclusions.

[Further studies requested]

Discussion
The evidence is accumulating and the doubt is thinning; the Antarctic ice sheets are shrinking at fantastic rates, and the rate of increase is itself increasing at a fantastic rate. Two years ago there might have been argument, but at this point it is obvious that something big is cooking at the south pole. The issue of causality is less complicated than Greenland, but still the strongest statement we can make is that warming is the only candidate known for the cause of the changes observed. Given the scale of the changes--and the recently discovered fact that ice outflow increases dramatically after ice shelves melt--I feel comfortable agreeing with the large majority of these researchers in this point: the loss of ice in Antarctica will likely reach astonishing proportions in the near future if current conditions persist. Two ice shelves collapsed in the last few years, triggering massive acceleration of glacial flow, and similar events should be expected in the near future.


A summary of the mass balance studies cited in this post:


Conclusion
This data constitutes strong evidence of north polar warming.

Sub-bullet value: TRUE

Sub-bullet a: Greenland

Sub-bullet a: "A clear warming trend is evidenced by the Greenland ice sheet"
Hierarchy: Part II:1:A:iv:a

Back to Intro - Back to Outline - Up to Bullet iv - Forward to Sub-bullet b

Introduction:
Greenland holds nearly 10% of all the ice in the world. Given its relatively southerly location, Greenland's ice is balanced precariously between its current state and cataclysmic melting, kept stable only by virtue of a microclimate controlled by the ice itself and by friendly and cold arctic ocean currents. The ice is so thick that the crust of Greenland is depressed in the interior from the weight of it. Warming should be relatively easy to spot here; many scientists think that Greenland is close to a sharp equilibrium point and that warming will cause a chain of " positive feedbacks"--some warming will trigger factors which compound the warming and trigger other factors, etc. Thus the changes in the Greenland ice sheet might happen quicker than expected given the large thermal inertia that such a huge block of ice has.

Greenland's climate is an anomaly when placed in the context of other land masses at its latitude. When my family traveled to Prudhoe Bay, AK this last summer, we found it warm and ice-free. Prudhoe Bay is at the northern edge of Alaska, at a latitude of 70 N [for comparison, Anchorage is at 61 N]. Greenland's permanent ice extends down to about 60 N, so far south that almost all of Alaska and the northern territories of Canada would be under ice if Greenland's ice sheet was typical. Why is Greenland covered in ice when most of the latitudes it occupies are free of ice elsewhere?

The glib answer is: because Greenland is colder than other areas at the same latitude. A little background is needed before we can answer why.

Greenland's ice sheet was formed during one of the many colder periods in the earth's history. These glacial periods have caused the latitude marking the ice sheet boundary to move southward, at times reaching down into the continental United States. About 10,000 years ago the last major ice age ended and temperatures returned to roughly what they are now. The equilibrium latitude shifted much farther north in a short period of time. The bulk of the ice sheets were now below the equilibrium latitude, and thus started slowly retreating northward. The retreat was so slow that it is probable that the remaining continental glaciers are still retreating to this day. For some reason, though, Greenland never got the message; some particular climate conditions caused the local equilibrium latitude around Greenland to be stuck farther south than it is for the rest of the Northern Hemisphere. It turns out that this effect is due to two main things: the East Greenland Current, an ocean current that cools Greenland's climate through shipping cold water right along the east coast Greenland from the Arctic; and the high altitude of the ice sheet in Greenland, which keeps the sheet colder than its latitude would dictate.

Warming would effect Greenland in very complex ways, and since the climate is dictated by an ocean current, understanding the subtleties of the current's response to warming would normally be critical to understanding the effect on Greenland's ice sheets. It would be impossible to delve into those subtleties here--albedo, salinity, feedback--but we can still draw some conclusions if the effects are clear enough. This requires an explicit logic that needs explaining: given the "well, duh" aspect of the statement "ice will melt more if temperatures increase" and also given that regional models predict a certain pattern of melting occurring as the result of the warming, IF expected melting patterns are conclusively observed, THEN the region is almost certainly warming. The burden of proof to the contrary will rest on those who wish to prove that the melting proceeds by some other mechanism.

I am not trying to cover up a logical flaw. Rather, I'm using the strongest logic that is possible in any kind of analysis of complex systems. A researcher can never be 100% confident in a causality solution in a system this complex, but it is not wrong to draw conclusions based on the best available data, assuming that as much rigor as is possible is dedicated to trying to understand the underlying causes and effects. Such a case this is. What this means practically is that we will look at the data, conclude confidently based on this data that it is TRUE or FALSE that the behavior of Greenland proves regional warming. The bullet value will only stay TRUE if sufficient evidence is not found for mechanisms other than warming causing the observed effects.
[Refer to bullet iv for further introductory material]

Study 1
Greenland mass balance from GRACE
Isabella Velicogna and John Wahr, GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L18505

Satellite gravity measurements confirm accelerated melting of Greenland ice sheet
J. L. Chen, et al., Science 313, 1958 (2006)

Recent Greenland ice mass loss by drainage system from sattelite gravity observations
S. B. Luthcke, et al., Science 314, 1286 (2006)

Basic: These papers utilize data from the GRACE experiment, with newer data in the second and third papers. This is the type of experiment every researcher would love to be part of. GRACE is a fantastic idea: two orbiting satellites working in tandem to measure the gravitational field above the earth. This is an exquisitely delicate experiment, but it was pulled off and is very successful. The idea is that ice will "pull" on the spacecraft through gravitational acceleration. This pull is measured each time the satellite passes over and compared across time. If the pull changes, that means that ice is accumulating or being lost on the ice sheet. The beauty of this approach is that it is independent of ice transport mechanism and is the first experiment that is directly measuring the quantity of ice present as opposed to indirect studies of depth or flow which use generous extrapolations and interpolations. The first study includes data from 2002-2004 and the second and third studies adds 2005 to that. The studies concluded that the mass balance of Greenland in the time period was large, negative, and accelerating, consistent with regional warming.

Details: Velicogna and Wahr: "We recover a decrease in total ice mass of 82 ± 28 km3 of ice per year." I am unable to access the rest of the paper, so I would appreciate anybody with an AGU membership to help me on this one. Again, although static or increasing mass balance is inconclusive, negative mass balance, especially one this large, is very strong evidence of warming. The image below, taken from the NASA site supporting this research, shows a very strong net mass loss around the periphery of Greenland and a small mass gain in the interior.

This figure, from Velicogna and Wehr, shows the total Greenland ice sheet mass observed by GRACE during the study:

The second study confirms this data and adds a crucial fact: melting accelerated even within the limited time scale of the study. This acceleration is evident in the following plots from Chen:
The second study revises the yearly net mass loss upwards and confirms the acceleration of mass lost at least on this small time scale.

The third study confirms the main results of the other studies but lowers the mass loss estimate from the second study.

GRACE tells us that the Greenland ice sheet is melting and by how much. But even more significant is that this melting is accelerating on a seasonal timescale. This is a crucial piece of the puzzle; receding glaciers can be attributed to "ice age rebound"--the still on-going process of ice retreat from the last ice age, when the ice sheets were much more expansive. But acceleration of melting can only be due to warming: rebound predicts a gradual deceleration of ice loss as the equilibrium point is approached.

Conclusion: GRACE data provides very strong evidence of north polar warming.

Study 2
Greenland ice sheet: high-altitude balance and peripheral thinning
W. Krabill, et. al., Science 21 July 2000:Vol. 289. no. 5478, pp. 428 - 430

Basic: Greenland ice sheet: high-altitude balance and peripheral thinning. What more to say?

Details: This study was conducted using laser altimetry from aircraft; this is how it was done before GRACE. Laser altimitry can only tell you the altitude of the surface of the ice so this approach is most useful for mass balance studies. The study specifically addressed the mass balance of Greenland. Above 2000m of altitude, there was a mass balance: net accumulation in the northern latitudes counteracted net loss in the southern latitudes. However, at all latitudes around the periphery there was widespread net loss. An included figure best describes the findings [flight tracks shown; also note that this is an elevation chart, not a mass chart like for GRACE]:

Although less comprehensive than the GRACE survey, it is clear that a large negative mass balance at the periphery of Greenland overwhelms the accumulation in the interior.

In sum: "Interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of ice per year from the entire ice sheet, sufficient to raise global sea level by 0.13 millimeter per year--approximately 7% of the observed rise."

Discussion: This study found strong evidence for behavior which points to warming: ice thickening or balance in the interior and aggressive thinning at the periphery. However, the authors admit that the peripheral thinning cannot be explained by the temperature record alone, and that the mechanism for the mass loss is still a mystery. Study 3 below is a partial response to this study and attempts to solve this problem with glacial dynamics studies.

Conclusion: This study gives some evidence for north polar warming.

Study 3
Changes in the velocity structure of the Greenland ice sheet
Eric Rignot and Pannir Kanagaratnam , Science 17 February 2006 311: 986-990

Basic: Using data from satellite radar interferometry [bouncing electromagnetic waves off the surface of ice from space], Rignot and Kanagaratnam have measured the velocity of the glaciers of Greenland over the last decade. Note how this differs from the previous study: the altimetry data presented in Study 2 likewise bounced electromagnetic waves [in that case, lasers] off the surface of the ice sheet, but there it was for the purpose of measuring the altitude of the ice surface and in this study the purpose is to measure the speed at which the ice flows down glaciers. These glaciers are the conveyor belts for ice transportation from the interior of Greenland to the sea, so glacial acceleration is a sign that more ice is leaving Greenland and entering the oceans. The study not only found widespread glacial acceleration, but found that the portion of Greenland experiencing the acceleration is increasing dramatically. The effect is also found to dominate any increase in due to warming, and is presented as an explanation for the mechanisms behind the results found in Study 2.

Detailed: The causes of glacial acceleration are not very well known, although all plausible explanations are products of warming [such as surface meltwater percolating down under the ice and lubricating the interface between ice and rock]. The degree of acceleration is also not a terribly good measure of the warming; all it can say is that warming is occurring. The study found that total mass loss from Greenland doubled in the period 1996-2005. The important point is that acceleration is observed, and this is not a feature of ice age rebound. The authors state: "We detected widespread glacier acceleration below 66 [degrees] north between 1996 and 2000, which rapidly expanded to 70 [degrees] north in 2005. Accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year."

The figure below shows the velocity plots of some of the glaciers from the study. The black lines correspond to the oldest data, blue the next, and red the most recent. Since these are velocity plots, the earmark of acceleration will be the red plots lying "above" the blue ones and the blue ones above the black ones.

Conclusion: This study constitutes strong evidence of north polar warming.

Other studies
Progressive increase in ice mass loss from Greenland
R. Thomas, et al., GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L10503

Basic: Similar results from the ICEsat experiment.

Quote: "Laser altimeter measurements over Greenland show increasing thickening rates bove 2000 m, reflecting increasing snowfall in a warming climate. But near-coastal thinning rates have increased substantially since the mid 1990s, and net mass loss more than doubled from an average of 4–50 Gt per year between 1993/4 and 1998/9 to 57–105 Gt per year between 1998/9 and 2004. This increasing trend is very similar to findings from independent massbudget studies, but differs widely from ERS radar altimeter results."

Runoff and mass balance of the Greenland ice sheet: 1958–2003
Edward Hanna et. al., JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D13108

Quote: "Runoff losses from the ice sheet were 264 (±26) km3 yr−1 in 1961–1990 and 372 (±37) km3 yr−1 in 1998–2003. Significantly rising runoff since the 1990s has been partly offset by increased precipitation. Our best estimate of overall mass balance declined from 22 (±51) km3 yr−1 in 1961–1990 to −36 (±59) km3 yr−1 in 1998–2003, which is not statistically significant."

The Greenland ice sheet and global sea-level rise
Julian A. Dowdeswell

Abstract: "The flow of several large glaciers draining the Greenland Ice Sheet is accelerating. This change,combined with increased melting, suggests that existing estimates of future sea-level rise are too low."

Seasonality and increasing frequency of Greenland glacial earthquakes
Göran Ekström, et al., Science 311, 1756 (2006)

Abstract: "Some glaciers and ice streams periodically lurch forward with sufficient force to generate emissions of elastic waves that are recorded on seismometers worldwide. Such glacial earthquakes on Greenland show a strong seasonality as well as a doubling of their rate of occurrence over the past 5 years. These temporal patterns suggest a link to the hydrological cycle and are indicative of a dynamic glacial response to changing climate conditions."

[Further studies requested]

Discussion
There is no doubt that Greenland is losing ice. And fast. A valid argument against concluding that warming is the cause of the loss is still present, however: since Greenland's climate is so controlled by the East Greenland Current [EGC], it is possible that the current is changing in ways that is encouraging the loss of ice on Greenland. The GRACE mass deficit maps are particularly encouraging to this line of thinking since a large majority of the mass loss occurs along the eastern coast, where Greenland and the current interface. I have dug deep to find evidence that the EGC has changed in any way since before the mass balance turned negative. I found no such evidence. Additionally, any change in the EGC could very well be tied to warming since the Arctic has seen the most dramatic effects attributed to warming of any region on Earth. Until strong evidence emerges that some other factor is forcing these dramatic mass losses, the sub-bullet value is TRUE. However, the evidence strength is demoted from "conclusive" to "strong" due to these concerns.

Brief summary of the issues: A complete description of the behavior of the Greenland ice sheet has to include two behaviors: ice mass loss--the change in the distribution and quantity of ice--and glacial dynamics--the change in the behavior of the ice. The dynamics data [such as Rignot and Kanagaratnam and Ekström] are strongly complementary to the mass balance data since glacial dynamics explains at least some of the mass loss and simultaneously acts as strong evidence of warming. Strong positive signatures of warming were found from both glacial dynamics studies and mass balance studies.

Summary of mass balance data:

Conclusion
This data constitutes strong evidence of north polar warming.

Sub-bullet value: TRUE

Bullet iv: Ice and Sea Levels

Bullet iv: "A clear warming trend is evidenced by ice sheet and sea level changes"
Hierarchy: Part II:1:A:iv

Back to Intro - Back to Outline - Back to Bullet iii - Forward to Bullet v

Introduction
It would be logical to assume that a warming world should be losing ice cover. But the relationship between warming and polar ice sheets is not simple. Warming does not simply melt ice; it also changes weather patterns that affect the accumulation of ice. Warmer polar air can carry more moisture and thus increase the amount of precipitation over ice fields, effectively increasing the amount of ice. If precipitation outweighs melting and evaporation [positive "mass balance"], then warming could actually increase the ice in polar fields. Also, the equilibrium-line altitude [ELA]--the altitude above which there is net ice accumulation--increases with increased temperature but decreases with increased snowfall, so it is not necessarily clear from ELA trends whether warming has occurred.

But it is still true that polar ice presents a potentially powerful testament to climate trends. The expected contribution to the mass balance from increased precipitation is small compared to increased melting. And also the distribution of ice changes in predictable ways according to temperature. Below the ELA, the rate of melting should undeniably increase with increasing temperatures. A signature of warming would then be ice thickening in the interior and thinning or retreating around the periphery. The flow of ice into the ocean is also expected to accelerate with rising temperatures; scientists have recently shown that the melting of sea ice abutting the mouths of glaciers triggers a massive acceleration of the glacier. And further evidence has been found that surface meltwater can percolate to the bottoms of glaciers and lubricate the ice-rock boundary, catalyzing faster ice flow. If sea levels are rising then the net amount of water tied up in ice worldwide must be decreasing, which would be an undeniable sign that temperatures are increasing despite increases in snowfall.

Glaciers and polar ice fields are very different beasts. Glaciers represent a much higher diversity of the planet's climates and thus tell us more about global temperature trends. Glaciers also are more a part of their surrounding climate than ice sheets in Greenland and Antarctica, which are so large that they create their own regional climates. So glaciers can respond faster to climatic variations. An analysis of ice cover then wouldn't be complete without a discussion of the trends in the distribution of continental glaciers.

Changes in the distribution of polar ice, glacial ice and sea levels are all important in an analysis of what ice can tell us about temperature trends. Each topic contains enough data to evaluate independently, so we will follow the structure below. Click on the links to see an analysis of the research for each topic.

Bullet Structure:

A clear warming trend is evidenced by ice sheet and sea level changes

a. The Greenland ice sheets show warming

b. The Antarctic ice sheets show warming

c. Global continental glaciers show warming

d. Sea levels show warming

e. Permafrost and river and lake ice show warming

Conclusion
No conclusion at this time.

Bullet Value: INCOMPLETE

Chuckwalla and Bunnies

Chuckwalla and I were looking up animal pictures on images.google.com, and she asked me to find pictures of a bunny. So I typed "bunny" and clicked on the first picture I saw.

Click on the link.

The photographer is... Steven Pinker! Pinker--the greatest modern cognitive psychologist, one of the most influential living linguists, and the modern anti-Empiricist rock star--took a picture of a "bunny." Not a desert cottontail rabbit, not a cottontail rabbit, not even a rabbit, but a "bunny." And not only that, but it is one of the top ten hits on images.google.com for "bunny."

Bizarre!

His gallery is actually pretty good. He uses polarizing filters to good effect, and he takes some nice macros. His bird pictures are all properly identified. But still... didn't see that one coming!

Bullet v: Warming and Life

Bullet v: "A clear warming trend is witnessed by changes in wild plants and animals"
Hierarchy: Part II:1:A:v.

Back to Intro - Back to Outline - Back to Bullet vi

Introduction
Most plants and animals rely on climate to provide the necessary conditions to provide essential sustenance. Additionally, living organisms rely on climate to provide weather cues essential to a complete life-cycle. Therefore, widespread warming should have a measurable effect on the life-cycles of many plants and animals. With increased temperatures, birds migrate and lay eggs sooner, populations tend poleward, and the physical and genetic traits of many species tend toward configurations ideal for warmer climates. Almost certainly a majority of these effects are not known, but those that are known are easy to measure and stand as a completely independent and reliable complement to temperature data. Accumulating data from these sources avoids many of the issues endemic to outright temperature measurements, such as instrumentation unreliability, faulty or problematic calibration, and lack of continuity or comprehensiveness of records. However species' traits are poor measurers of the degree of the warming, meaning that their use is restricted to orthogonal verification of more standard climatic data.

Study 1:

Fingerprints of global warming on wild animals and plants
Terry L. Root et. al., Nature 421, 37-42 (2 January 2003)

Basic: A large meta-analysis of 143 independent papers which shows that the large majority [>80%] of nearly 1,500 plant and animal species studied had significant changes in behavior, habits, and physical traits consistent with rising temperatures but not consistent with level or decreasing temperatures. The trait shifts were statistically significant in the direction consistent with warming.

Details: The species' traits studied included population density change and poleward migration; phenology: the timing of egg-laying, flowering, migration, etc.; morphology: body size, behavior, etc.; and genetic frequency shifts. The meta-study identified potential temperature-dependent shifts for each species and counted the number of observed shifts of these types. Over 80% of the species showed shifts consistent with warming, with a 90% confidence interval of roughly 70%-89%. The shifts in phenology [timing of life-cycle events] across species shows statistically significant trends towards earlier dates.

In sum: "...the balance of evidence suggests that a significant impact of recent climatic warming is discernible in the form of long-term, large-scale alterations of animal and plant polulations. For example, the average shift in spring phenology (timing) of events, such as breeding or blooming, for temperate-zone species is 5.1 +/- 0.1 days earlier in a decade."

Discussion: It is important to note that this study does two important things: [1] confirm a wide-spread and broad-based response consistent with a global warming trend, and [2] act as an independent, statistically verified, though imprecise, verification of the IPCC warming data. Though the IPCC data were cited in the study, it is crucial to understand that the trait shift data exist independent of any warming data and no statistical results were contingent on IPCC data.

Conclusion: This meta-analysis is very strong evidence of a widespread warming trend.

Study 2:
Biological fingerprint of climate change impacts
Camille Parmesan & Gary Yohe, Nature 421, 57-60 (2 January 2003)

Basic: A large meta-analysis of over 1,700 species focusing on range and phenology shifts as well as relative abundance shifts. The shifts are compared to predictions based on IPCC climate warming data and agree with a confidence of >95%. This means that there is a less than 5% chance that the living systems' shifts that have been observed are correlated with the IPCC warming data purely by chance.

Details: Northern range limits for species moved an average of 6.1 km per decade northward with 95% confidence interval of 1.3-10.9. Mean spring timing advanced an average of 2.3 days per decade, with 95% confidence interval of 1.7-3.2. The entire set of analyses points to a >95% [the IPCC's definition of "very high"] confidence that climate change is driving species poleward and pulling spring dates earlier.

In sum: "The meta-analyses of 334 species and the global analyses of 1,570 species... show highly significant, nonrandom patterns of change in accord with observed climate warming in the twentieth century, indicating a very high confidence (>95%) in a global climate change fingerprint."

Discussion: This is perhaps the most statistically rigorous paper on the topic. Conforming to very high levels of objectivity and statistics, the evidence overwhelmingly proves that global plant and animal life is changing in ways consistent only with global warming. We endeavor in this section only to show that plants and animals are changing in ways that signal global warming, but it is interesting to note that this paper also ties the degree of living organism response to the amount of warming and thus acts as a kind of verification of the actual IPCC warming data.

Conclusion: This meta-analysis is very strong evidence of a global warming trend.

Study 3:
[Various phenology studies]
Mark D. Schwartz
[as suggested by reader "Smoker"]

Basic: Schwartz has made a career out of creating an integrated study of phenology. He utilizes ground stations, citizen scientists, networks of researchers and satellites to track the onset of spring and to measure trends in the timing of leafing and blooming. There is no simple way to synthesize all of his findings here, but there is a very useful collection of figures on his website relating to a single study he conducted which is indicative of the type of data he is collecting. The figures for growing season length, last spring freeze date, first bloom date, and first leaf date trends are particularly instructive. Data from stations across the Northern Hemisphere were used for the study.

One pertinent quote: "Results are consistent with prior smaller area studies, confirming a nearly universal quicker onset of early spring warmth (spring indices (SI) first leaf date, -1.2 days per decade), late spring warmth (SI first bloom date, -1.0 days per decade; last spring day below 5 1C, -1.4 days per decade), and last spring freeze date (-1.5 days per decade) across most temperate NH land regions over the 1955–2002 period."
[Quoted from: Onset of spring starting earlier across the Northern Hemisphere, Mark D Schwartz et. al., Global Change Biology (2006) 12, 343]

Conclusion: This body of data is very strong evidence of a widespread warming trend.

Further studies on the topic:

Patterns of phenological changes in migratory birds
Thorup K et. al., Oecologia. 2007 Apr;151(4)

Rapid advance of spring arrival dates in long-distance migratory birds [with response]
Jonzen N, et. al., Science. 2006 Jun 30;312(5782)

Climate correlates of 20 years of trophic changes in a high-elevation riparian system
Martin TE, Ecology. 2007 Feb;88(2):367-80

Conclusion
These studies together constitute conclusive evidence of a global warming trend. Little information about the rate and scale of the warming is discernible from this data, however. No papers I have found to date can attribute these trait shifts to any other cause than increasing temperatures, so this bullet is uncharacteristically clean and simple.

Bullet value: TRUE

Back to the Outline

Please Spend This Here $10,000,000,000

The Bill and Melinda Gates Foundation has just offered you one-quarter of its endowment--10 billion dollars--to spend on charitable endeavors of your choice. They also stipulate that you must spend it or lose it; no investments possible. What would your plan be? Be specific and thoughtful, I'm very interested in your answers. My guess is that the answers will vary drastically. I'll include all of the responses in a main post when enough people have responded, unless you request otherwise.

Have fun!

Again, what should I write about?

This time, pick 3 and rank them. I'll do every one that gets a vote before I ask this again! And this time, there is no reason for the order.

Book reviews:
1. The World Without Us by Alan Weisman [5 stars]
2. Resistance by Barry Lopez [4.5 stars]
3. 1491 by Charles C. Mann [2.5 stars]
4. Nature via Nurture by Matt Ridley [4.5 stars]
[4.5. Doomsday Book by Connie Willis [4 stars] -- it's difficult for me to review novels but I'll try really hard if you REALLY want it]

Philosophizationings:
5. The demise of the clovis megafaunal extinction theory
6. Thoughts on asceticism
7. The Project for the New American Century
8. The chimp video game study fraud
9. The first Global Warming data
10. Why I might never have a real job [aka "The 2008 DOE Science Budget"]
11. Why the election system is broken
12. Cranks, kooks, crackpots, and their relationship to science... and birding

[There are 12 delegates up for grabs. Delegates will be assigned in a proportionate distribution based on voters' number 1 picks, except when a particular candidate topic receives less than 15% of the possible vote, in which case its delegates will be transferred to the second choices of the voters casting the unpopular first pick. If your second choice also receives less than 15% of the vote, all of your votes will contribute delegates to your third choice. If the third choice is under 15% then your votes will be discounted. Additionally, I posses 6 superdelegates which I will assign based on whimsy after the vote which will guarantee that I will first write whatever topic I really want first. But don't let that dissuade you, vote away!]