Funmurphys: the Blog

The Triumph of Hope over Experience

Posts Tagged climate

Done With Coursework

May 16

Posted by Carl Drews in Education, Science | No Comments

Wow! After 4 years of graduate school I have completed all my coursework for the Master’s Degree. This is amazing to think about! I took one course at a time, focusing on the journey rather than the destination. But here I am!

My thesis year is next. I plan to research my fingers to the bone and defend my thesis in Spring 2009. And then graduate! I enjoyed my classes, and now I’m looking forward to independent research on wind-driven storm surge. If I had started the Master’s program earlier maybe I could have helped those folks in Myanmar to avoid getting clobbered by Cyclone Nargis. But I’m sure there will be other chances to save lives . . .

The University of Colorado web site has this nifty Grade-O-Matic feature that calculates your grade point average whenever you complete another course, and the Grade-O-Tron meter says my GPA is 3.763. I guess I’m not gonna flunk out of grad school after all! I even managed to pull an A- in Fluid Dynamics. Any course with “dynamics” in the title is tough.

My Oceanography class was neat because we used real data and analyzed all the layers in the world’s oceans. Ocean water masses form in certain regions and retain those same properties even when they travel long distances. The Atlantic Ocean is most stratified. For example, here is a meridional cross section of the Atlantic Ocean at 30 degrees West:

http://acd.ucar.edu/~drews/AtlanticSection30West.jpg

That big purple blob descending from the upper left-hand side of the plot is Antarctic Intermediate Water (AAIW). The AAIW water mass stabilizes at about 1000 meters deep and spreads all the way up to 10N. AAIW is cold and fresh from ice melt; cold enough to slide below the warm tropical salty water, but fresh enough to stay above the saline North Atlantic Deep Water. Way cool!

I took a couple of classes on climate and the human affects on same. From what I learned, the vast majority of climate scientists believe the earth is getting warmer, and a smaller majority believe that humans are a major cause of this warming. One of my classes was taught by Roger Pielke Sr., who might be considered a climate-change skeptic (and he’s a real scientist, not like Rush Limbaugh). Dr. Pielke agrees that increased carbon dioxide is a warming perturbation, and that humans produced the CO2 increase. But he contends that land-use change (irrigation, urbanization, agriculture) is a bigger factor in anthropogenic global warming. When you water the desert and farm it, the decrease in albedo (brightness) absorbs more sunlight and warms the planet. Pielke showed some stunning examples of the changes humans have wrought on the land surface! Stunning in terms of the albedo change and the total percentage of the land surface we have have touched (40%). I carried out a simulation experiment on Aboriginal Australia with the Community Atmospheric Model (CAM) that supported Pielke’s contention that land-use changes can be comparable in magnitude to CO2-driven changes, but my study region was too small to apply this finding to the entire globe.

In Genesis 1:28 God tells mankind to subdue the earth and have dominion over all other living creatures. Genesis 1:28 strongly implies that humans can have a very real affect on the planet’s ecosystem, for better or worse. So from the Biblical perspective it’s reasonable to conclude that human activities can indeed alter the global climate. We aren’t big enough individually, but there are 6 billion of us, and we’ve been fiddling with the earth for quite a few years now.

I looked for evidence relevant to carbon dioxide forcing. Can human-raised levels of CO2 really warm the planet? Is there any historical analog to the current situation? The timing of CO2 vs. temperature changes in the Antarctic ice cores is a little hard to determine precisely, because CO2 has a nasty habit of diffusing deeper into the snow before compaction. A good scientific publication is: “Timing of Atmospheric CO2 and Antarctic Temperature Changes Across Termination III”, by Nicolas Caillon et. al.; 14 MARCH 2003 VOL 299 SCIENCE www.sciencemag.org, page 1728. They postulate the following sequence:

1. Time 0 years: Antarctica gets warmer due to orbital forcing (the trigger).
2. Time 800 years: Change in ocean circulation leads to global rise in carbon dioxide.
3. Time 5,000 years: Northern Hemisphere completes its de-glaciation, caused by CO2 amplification of the original orbital forcing.

Caillon states that “the CO2 increase clearly precedes the Northern Hemisphere deglaciation (Fig 3).” One might think that we have 5,000 years to wait before the Northern Hemisphere completely de-glaciates, but don’t get cocky! – Termination III is not a perfect analog to today’s situation. The point is that increased CO2 really can, and has, forced higher global temperatures.

On a final note: Science in action is really good to see! Conclusions really are reviewed, examined, and questioned by other smart people. We scientists are human, but we are committed to finding out the truth. Sometimes the scientific process includes disagreements along the way. I’m excited about my entry into the process!

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Ride My Bipolar SeeSaw

Nov 10

Posted by Kevin Murphy in Science | No Comments

Everything old is new again, and today’s example is the so called Bipolar Seesaw freshly discovered. The bipolar seesaw is the swing in temperatures between the two poles of earth, where if its up in one pole its down in the other. But how freshly discovered is it? Well, here’s an article from 1998 about — ta da — the bipolar seesaw, complete with polar ice cores showing temperature fluctuations.

Even more interesting is this 2001 article by Wallace S. Broecker that ties it all together:

Geologists are now investigating whether these groupings correspond to another new source of evidence of cyclic patterns in Earth’s recent history. This evidence comes from studies of sediment in the deep waters of the North Atlantic. The rock fragments in these sediments are much too large to have been transported there by ocean currents; they could have reached their present location only by having been frozen into large icebergs that floated long distances from their point of origin before melting. During the past decade, Gerard Bond, my colleague at Columbia University’s Lamont-Doherty Earth Observatory, has studied the makeup of such ice-rafted debris. Noticing that some of the sediment grains were stained with iron oxide, he reasoned that they must have come from locales where glaciers had overrun outcrops of red sandstone. Bond concluded that a detailed analysis of deep sediment cores would reveal changes in the mix of sediment sources over time. This proved to be an excellent strategy, for Bond found something so unexpected that it stunned all of us who study climate history. The proportion of these red-stained grains fluctuated back and forth over time from lows of 5 percent to highs of about 17 percent, and these fluctuations had a pattern: a nearly regular, 1,500-year cycle. Even more amazing, he found that the cycles ran virtually unchanged, in both amplitude and duration, through both ice-age and non-ice-age periods during the last 100,000 years.

Bond puzzled over what might be pacing this cycle. As a geologist, he knew that the sources of the red-stained grains were generally closer to the North Pole than were the places yielding a high proportion of “clean” grains. At certain times, apparently, more icebergs from the far north were making their way well to the south before finally melting and shedding their sediment. Bond hypothesized that the alternating cycles might be evidence of changes in ocean-water circulation.

Ocean waters are constantly on the move, and water temperature is both a cause and an effect. As water cools, it gets denser and sinks to the bottom. In one part of what I like to call the “bipolar seesaw,” the bottom layer of the world’s oceans comes from cold, dense water sinking in the far North Atlantic. This causes the warm surface waters of the Gulf Stream to be pulled northward, as they are today. Bond realized that during this part of the ocean cycle, a large proportion of the icebergs that bear red grains would melt while still fairly far north. But sometimes the ocean reorganizes itself, and the Southern Hemisphere holds sway in driving ocean circulation. At such times, surface waters in the North Atlantic would generally be colder, permitting icebergs bearing red-stained grains to travel farther south before melting and depositing their sediment.

So what we have is just more confirmation, not anything new with the latest announcement of findings. Although I can’t complain too much, because it was new to me.

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Radiocarbon Dating and Climate Change

Jul 18

Posted by Carl Drews in Science | 2 Comments

Last Saturday I took the kids up to the Mesa Lab to see the “Climate Discovery” exhibit at the National Center for Atmospheric Research (NCAR). NCAR has a lot of graphs and other illustrations about climate change. I asked the tour guide how the climatologists sort out which is the cause and which is the effect, between carbon dioxide and temperature?

The guide brought out Caspar Ammann and Carrie Morrill, both of whom I knew from past presentations (they both have PhDs). This was a public conversation at a public event, so I can report it here. Caspar pointed out the correlated graphs of CO2 and temperature proxies, taken from the Vostok ice core (~420,000 years). He remarked that it is difficult to sort out cause and effect from the ice cores alone. As the air bubbles become trapped in the ice during compression over the first 100 years or so, some CO2 migrates by diffusion between the annual layers. The effect is that the annual CO2 and temperature signals are not as precise over very short time scales, and the lead/lag relationship between the peaks can be obscured. I didn’t pursue this line of inquiry further because I plan to investigate the ice core data myself as a project for Climatology class during the upcoming fall semester.

However, Carrie told me that the increase in CO2 displayed by the Keeling Curve can indeed be attributed to human burning of fossils fuels, and here’s how: The air is getting older. Carbon-14 has a half-life of 5,730 years, and it can be used to date objects up to about 50,000 years old. Carbon-14 decays into Nitrogen-14 through beta decay:

http://en.wikipedia.org/wiki/Carbon-14

Objects older than 50k years have only the N-14 isotope. By measuring the ratio of Carbon isotopes in organic material, one can determine how many years have passed since that organism was last exposed to the air. We can measure the age of all this carbon dioxide that’s building up in the atmosphere. The following article at RealClimate.org states:

How do we know that recent CO2 increases are due to human activities?

http://www.realclimate.org/index.php?p=87

“Sequences of annual tree rings going back thousands of years have now been analyzed for their 13C/12C ratios. Because the age of each ring is precisely known** we can make a graph of the atmospheric 13C/12C ratio vs. time. What is found is at no time in the last 10,000 years are the 13C/12C ratios in the atmosphere as low as they are today. Furthermore, the 13C/12C ratios begin to decline dramatically just as the CO2 starts to increase — around 1850 AD. This is exactly what we expect if the increased CO2 is in fact due to fossil fuel burning.”

I spent some time looking for a graph of Carbon isotope ratio vs. time that would show the “dramatic” change at 1850, but couldn’t find one. If you have a link, please post it below.

If temperature rise were currently forcing CO2 rise “naturally”, we would expect newer CO2 to get flushed from the earth’s surface. But it’s old CO2 that’s getting flushed instead, and the most obvious cause is human burning of fossil fuels.

The astute reader may wonder, How do we know that the older CO2 isn’t merely coming out of the Arctic peat bogs? The bogs will flush more CO2 as the Arctic climate gets warmer, and peat bogs are really old.

Carl’s answer: The trend of older atmospheric CO2 has been going on since about 1850, which is the start of the Industrial Revolution:

http://www.ipcc.ch/present/graphics/2001syr/large/02.01.jpg

Global temperature rise didn’t really get going in earnest until about 1975. We’ve only been flushing out the peat bogs for about 30 years, not 150 years:

http://www.ipcc.ch/present/graphics/2001syr/large/05.16.jpg

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… And Love Global Warming

Jun 29

Posted by Kevin Murphy in Science | 7 Comments

I’m going to buy me a nice big straw hat, lots of sunscreen, and lose enough weight to look good in my new swimsuits. Because I’m hoping Mr. Gore is right and I’ll have beach front property here in Missouri in a few months. Why not celebrate the Earth getting warmer when the alternative is that it will get colder, and I know which one of the two I prefer. Even if you think that global warming has something to do with what people are doing (and I don’t), I figure that since it’s taken us decades to put carbon dixoide into the atmosphere it will take decades to get it back out which means it’s going to be around a while so you might as well enjoy the ride.

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