Week 13 - Packrat Middens

This week we'll be reading:

Smith, Felisa A. and Julio L. Betancourt. 2006. Predicting woodrat (Neotoma) responses to anthropogenic warming from studies of the palaeomidden record. Journal of Biogeography 33: 2061-2076.

You might recognize the name of the first author as our official faculty member, Felisa! This is a paper on using middens to study how packrats have reacted to changing temperatures over time.

This paper focuses on using fecal pellets to study body size change in the woodrats. Traditionally the data sources from packrat middens are plant macrofossils and pollen. These are analyzed in a similar way to pollen from lake cores that we discussed earlier in the semester. We'll talk about using these data in class.

Packrat paleomiddens can also contain other material from the environment, such as archaeological artifacts, bones, and teeth. I'll probably throw in some teeth, since that's what I study for my research.

For our discussion on Thursday, I want you to start thinking about designing studies of your own. How has climate change affected species and ecosystems in the past? Design a study and post it in the comments.

Week 12 - Tree Rings

This week we'll be reading:


Li, Jinbao, Edward R. Cook, Rosanne D'Arrigo, Fahu Chen, Xiaohua Gou, Jianfeng Peng, and Jianguo Huang. 2008. Common tree growth anomalies over the northeastern Tibetan Plateau during the last six centuries: implications for regional moisture change. Global Change Biology 14: 2096-2107.


This week, when you are reading the paper about tree rings and climate in Tibet, be thinking about how those methods could apply to other studies.  Last week, we had a good discussion regarding the collapse of Copan.  If you were to conduct a study using tree rings and similar metrics to those used in the Tibet study, how would you apply those to Copan to answer hypotheses?  What other metrics would be useful?  Be specific about your hypotheses and sample sizes and describe what your hypothetical dataset would look like.  What other forms of data would be useful to determine the Copan collapse?  Think of at least three.  Be prepared to discuss your hypothetical experiment and blog post and have the class scrutinize them like we did for the palynology paper last week!

Week 11 - Palynology

This week we're learning about using pollen records to learn about paleoclimate. We'll be reading:

McNeil, Cameron L., David A. Burney, and Lida Pigott Burney. 2010. Evidence disputing deforestation as the cause for collapse of the ancient Maya polity of Copan, Honduras. PNAS 107:3, 1017-1022.
(Note that on the wiki, the paper is listed as McNeil et al 2009 - this is a typo.)

As you read this paper, think about how the data are analyzed and interpreted. What, if anything, would you have done differently with the pollen data?

Week 10: Fires, Landscapes and Climate

This week we will be investigating how changes in climate can affect the landscapes that we observe and also how landforms can be useful in understanding past climate.  In particular we will be looking at fire events.  In a changing world where the frequency of large stand replacing fires appears to be on the rise there is a need to understand how "abnormal" these fires are (Whitlock, C., 2004. Forest, fires and climate. Nature, 432, 28-29. This is posted as an intro to this week's topic).

The primary reading this week will focus on fire records from the Sacramento Mtns in southern New Mexico and is written by UNM folks!

Frechette, J.D., Meyer, G.A., 2009. Holocene fire-related alluvial-fan deposition and climate in ponderosa pine and mixed-conifer forests, Sacramento Mountains, New Mexico, USA. The Holocene, 19(4), 639-651.


It is about 10 pages, but there are lots of figures.  Pay attention to what the figures are trying to tell you as you read. Enjoy!

The Whitlock paper is optional, but highly recommended as a short, concise intro to the topic. It is posted on the wiki along with the primary reading.

For your blog post prior to Thursday's class here are a few questions to consider in your response:

1. What was one thing that you found interesting in the paper?
2. Is there one thing that you have questions about after reading the paper?  What were you confused by or feel you need more information about?
3. Were you convinced by the story that the authors proposed in the paper?  Why, why not or why maybe?  Be specific.

Final Project Discussion

Hey folks, it's finally time to start working on your final projects! I have posted the guidelines for your projects on the wiki. The gist is, you need to do an original analysis of freely available data or do a meta-analysis related to climate. I'm posting this entry so you can kick around ideas and ask questions in the comments. I hope you'll all keep an eye on this entry and help each other out.

Week 9: Microwear and Climate Change

Hey folks,

This week I want to do a special prompt for our blog discussion.  Of course, you may, as usual ask and answer questions about this week’s article on microwear, but I thought it’d be really fun to continue a discussion on current climate changes, its effects, and how we as a scientific community interpret and convey our results to the general public.

On last week’s blog, Mike provided some very extensive and excellent research articles regarding current mass extinction.  However, since I am a firm advocate of the scientific method and a proponent of questioning any study under the name of science, I’d like to play devil’s advocate for a moment and pose a few thoughts in response to the assertion that we are currently undergoing a mass extinction:

1)      The fossil record is not always a good proxy for past environments.  Barnosky and colleagues exclusively looked at mammals, citing that, on average, over the past 65 million year only 2 species per year went extinct.  Personally, I am a little concerned about this assumption because there is an obvious bias toward preservation of larger mammals over smaller and I believe it impossible to know the extinction rate of some of the smaller fauna not preserved in the fossil record (this is particularly pertinent since smaller mammals generally have a faster species turnover, fast-slow continuum anyone?).  Although the authors address this problem in their article and state our incomplete knowledge of extant species, I still believe these two records are not quite comparable.

2)      Some species have responded already to current climate change and I believe we will continue to see some species adapt and (potentially) a decline in the rate of extinction . Here’s just a short little review artcile on the subject from 2002, I’m sure much more has been explored since then: http://eebweb.arizona.edu/courses/Ecol206/Walther%20et%20al%20Nature%202002.pdf .  I also came across this article: http://www.law.arizona.edu/AdaptationConference/PDFs/ParmesanAREES_Impacts2006.pdf which, while it definitely emphasizes concern over the ability of animals to adapt sufficiently to climate change and  is a nice (albeit longer) review.

3)      Although I noticed that many of the articles mentioned in last week’s blog deal with increased rate of extinction in individual species(which I by no means doubt, I believe we have ample evidence), only a few deal with mass extinction, which is a whole other animal.  While I do believe that theoretically we could be heading in that direction, the studies explicitly dealing with mass extinctions are still projections. The actual rate of extinction, all animals taken together, is still not near the landmark of 75% of all species eliminated at the moment.    When all is said and done, we cannot be certain which animals will be able to exploit these new habitats and what new species will develop from this event (and believe me, a lot more research effort has been focused on looking at extinction, not speciation). I have no doubt that species diversity will decline (and has!) but I am still unconvinced it is on the level of a mass extinction at the moment.  I have a hard time accepting Barnosky’s assumption that threatened means inevitable extinction in the near future. However, I agree, without conservation efforts for threatened species, we are more at risk of entering a mass extinction.    I personally think we should continue conservation efforts full-force, but I do not believe there is ample evidence to call our current state a mass extinction (at the moment, though I’m open to having my mind changed with sufficient evidence). ….though I am considerably more worried about amphibians and coral now…

As I said, I am primarily worried about agriculture and while I by no means think we should flout conservation efforts, I do think we should address agriculture.  I turn it over to the peanut gallery though, what concerns you most and why?  If you want to debate my questioning of the mass extinction, I encourage it! Think of this as a free forum for the rest of the semester to discus climate change and its impacts.  Here’s a few questions to kick you off:

1)      What concerns you most about our current climate change?  (articles are always encouraged!)  Be ready to defend your answer…there are always multiple sides to one story and, as scientists, we must be as impartial as possible…..which means we’ve got to play devil’s advocate to our own initial proclivities.

2)      Whether we are going through a mass extinction or not, I have mixed feelings on the way it should be conveyed to the general public.  Sometimes a more extreme prompt can be very encouraging for change (which, of course, is a good thing!) though, unfortunately, sometimes it can have the opposite effect of isolating more conservative-minded folk who don’t put as much stock in science.  How do you think we should convey current issues to the general public?

3)      As students of science (who I hope will continue to be actively involved in looking at global climate change….and coming up with a few solutions…) how do you think we should approach climate change effects in the future?  

As always, you guys may discuss this week’s article as well…impressions, concerns, ideas for future research, I’m all ears!

Have fun and see you all on Thursday for some more fun with microwear!

Katie

Isotope Projects

Hey Folks! Sorry for the delay! Your isotope project descriptions and data are now posted on the wiki page.

Readings for the week after spring break are also now posted.
 

Week 8: Carbon and Nitrogen Isotopes

Hi folks! The reading for this week is as follows:

Wilson AS, Taylor T, Ceruti MC, Chavez oA, Reinhard J, Grimes V, Meier-Augenstein W, Cartmell L, Stern B, Richards MP et al. . 2007. Stable isotope and DNA evidence for ritual sequences in Inca child sacrifice. Proceedings of the National Academy of Sciences 104(42):16456–16461.

For this week’s discussion, here are some questions you may want to think about:

1)      What do you think about the author’s explanation for the oxygen and hydrogen isotopic trends in the Llullaillaco children?

2)      Look carefully at the δ¹³C and δ¹⁵N patterns for the children, do you notice any anomalies or incongruencies with the authors’ explanations for the diet in the months prior to sacrifice?

3)      How could changing landscape through the children’s journey impact δ¹³C and δ¹⁵N values?

We did not go over sulphur in class and I don’t expect you to understand it all from the article, but if you want a good background in sulphur I suggest this article: http://email.eva.mpg.de/~richards/pdf/Richards_IJO_Sulphur.pdf

Happy Reading!

Week 6+: The data

Good luck with your ice core data projects this weekend.  Let us know if you run into problems.  The point is to learn how to deal with and look at real data from one of our climate proxies, in this case, ice!  Some banging of the head against the wall is required, but if you start getting a headache contact us, post on the blog, contact classmates and hopefully we can have some fun with this.

The assignment, figure of Vostok del18O periodicities that we discussed at the end of class and the code that generated said figure are all up on the class wiki.

Cheers (with plenty of ice in your glass),

Bekah

P.S. Very relevant CLIMATE LECTURE: Dr. Stephen Pekar of Queens College, "Past Climate Changes in Antarctica: Looking Back to Our Future"  Friday February 24, 2012, 2 pm, Northrop Hall Rm 122

Week 6 - Ice Cores

Lucky you - this week we have no preliminary reading for the lecture.

Last week's work with ocean cores will help immensely.  Keep in mind everything you learned about oxygen isotopes.  They are coming back to haunt you again this week!  Bring along your laptops for lecture as we will begin working on our ice core project during Tuesday's lecture. See you in class.

Week 5 - Deep Sea Cores

The article for this week is:
Bohaty, Steven M. and James C. Zachos. 2003. Significant Southern Ocean warming event in the late middle Eocene. Geology 31:1017-1020.

As you're reading this paper, try to keep the QuALMRI format in mind. What is the question for this paper? What inferences does it make? etc. Some other questions to think about are:

What important assumption is made in the oxygen isotope analysis of this paper? Do you think it's appropriate?

This paper includes an analysis of carbon isotopes, which we haven't talked about yet. Why do you think these researchers were interested in carbon isotopes? What did they learn from them?

What implications does this study have for the climate change event we are currently experiencing?

What research would you like to do to evaluate the results of this study?

Week 4 - Stable Isotope Introduction and Oxygen Isotopes

Hi folks! Great to see some people already getting psyched about isotopes!  The reading for this week is: 

Ehleringer JR, Bowen GJ, Chesson LA, West AG, Podlesak DW, and Cerling_ TE. 2008. Hydrogen and oxygen isotope ratios in human hair are related to geography. Proceedings of the National Academy of Sciences 105(8):2788–2793.

For this week’s discussion, here are some questions you may want to think about:

1)      How did the author’s parameterize their model? Given the ‘effects’ we talked about in class, are their model results what we would expect?

2)      Do you think the model was effective? Why?

3)      How can we apply this model to other fields, such as forensics?

Happy reading!

Week 3 - Stratigraphy

Hi folks! The reading for this week is as follows:

DeKock MO, and Kirschvink JL. 2004. Paleomagnetic Constraints on the Permian-Triassic Boundary in Terrestrial Strata of the Karoo Supergroup, South Africa: Implications for Causes of the End-Permian Extinction Event. Gondwana Research 7(1):175-183.

This paper uses paleomagnetic reversals in combination with known stratigraphic data marking the Permo-Triassic boundary to compare the timing of the end-Permian extinction of terrestrial organisms to that of marine organisms.

For this week’s discussion, here are some questions you may want to think about:

1)      Do you think there methods were appropriate to examine the differences between the end-Permian extinction in marine and terrestrial environments?  Why or why not?

2)      In light of what we learned in class on Tuesday, what do the strata imply about the terrestrial environment at the Permi-Triassic boundary?

3)      If, as the authors posit, the marine and terrestrial events were diachronous, how can we test if a causal relationship exists between the two?

As always, these questions are only suggestions and you are free to bring up any other insights/questions/concerns about the article.  Have fun and see you on Tuesday!

Week 2 - Paleogeography and Paleomagnetism

This week’s discussion paper : 

Angiolini, L., Gaetani, M., Muttoni, G., Stephenson, M.H., Zanchi, A., 2007. Tethyan oceanic currents and climate gradients 300 m.y. ago. Geology, 35(12), 1071-1074. 

Angiolini et al. (2007) are using many of the principles that we discussed on Tuesday, related to paleogeography, to attempt to explain the fossil assemblages that the authors have found in Iran.  Let us know what you think of the paper.  Below are a few questions to guide your discussion. 

1. Given that the paleomagnetic discussion in Angiolini (2007) contains jargon that we may not all understand, how solid do you feel that the paleogeographic reconstruction is?  What issues might arise from this?
2. It is easy to get lost in the weeds with terminology presented in this week’s paper.  Without worrying too much about brachiopods and statistics what is the study of the fossil record trying to show in this particular study?  How convincing is the authors’ story?

As always, if there is something that totally blows you away, or leaves you more confused than you ever thought possible, feel free to post your thoughts and questions, so that we may be able to address these things in discussion on Thursday. 

Week 1 - Snowball Earth

This week, as an exciting opening to the course, we're reading about the Snowball Earth hypothesis. This hypothesis states that, at three or four time periods between 2220 million years ago (mya) and 560 mya, the earth was completely covered in ice. There are multiple lines of evidence supporting the Snowball Earth hypothesis, the most important of which is glacial deposits from this time period on all continents, even those which were located in the tropics. These deposits are often covered by carbonate rocks, called cap carbonates, that could have been formed during rapid warming events following long periods of glaciation. Ratios of C13 (a stable carbon isotope) to C12 in these rocks are consistent with a decrease in biological activity during each glaciation. There are several proposed causes of these glaciations. One of these is the breakup of the supercontinent, Rodinia, and the migration of the smaller continents into tropical regions. (Hoffman and Schrag 2000). This hypothesis is tested in our primary research paper for the week, Donnadieu et al. 2004.

The breakup of Rodinia could have caused an increase in rainfall, because smaller continents with greater shoreline could be exposed to more rainfall. Rainfall, in turn, causes weathering of CO2 from land into the ocean, leading to decreased CO2 in the atmosphere. This could eventually result in ice forming at the poles, spreading slowly toward the equator. Ice reflects sunlight from the Earth's surface back into space, which would cool the Earth further, a phenomenon known as albedo. This positive feedback loop could result in complete or near-complete glaciation of the earth. Donnadieu et al. (2004) use climate models to test the hypothesis that the breakup of Rodinia could decrease the levels of atmospheric CO2 enough to initiate this process. They find that increased weathering resulting from changes in geography could have lowered Earth's average temperature by around 8 C, a level able to trigger a full glaciation.

In your comments, and for class on Thursday, think critically about this hypothesis. Do you think evidence is sufficient to support a Snowball Earth? What evidence is there against a Snowball Earth? What are your thoughts on using a modeling approach to study this problem? How would you study this problem? How do you think life could have survived during a Snowball Earth climate? How could the climate have escaped from a Snowball Earth glaciation? Most importantly, what questions do you have about the Snowball Earth hypothesis?

Citations:

Donnadieu, Yannick, Yves Godderis, Gilles Ramstein, Anne Nedelec, & Joseph Meert. 2004. A 'snowball Earth' climate triggered by continental break-up through changes in runoff. Nature 428: 303-306.

Hoffman, Paul F. & Daniel P. Schrag. 2000. Snowball Earth. Scientific American 282: 68-75.

Week 0

This is a test post. Next week we will be reading our first scientific paper and doing an introduction to the climate system. I will post the syllabus, course schedule, and e-reserves information when I have it.