Eemian Globe

I've created a rotating globe modelled after the Eemian interglacial, ~125,000 years ago.

 

Eemian Globe

I've been using this model to illustrate a series of posts by Steve Brown on Skeptical Science:

http://www.skepticalscience.com/LIG2-1906.html

http://www.skepticalscience.com/LIG3-1207.html

My goal was to portray a plausible shape to the Eemian sea, which cut Scandinavia off from the mainland. While at it, I erased part of Florida (in case Eemian sea level reached the high estimate of 9 meters over current) and much of the deltas next to major rivers. Like all my projects, this is a work-in-progress and I invite comments and corrections.

jg

Epica Vostok Viewer Update

Since having the honor of sharing my data viewer project on Skeptical Science, I've been working on a list of feature requests. I think I have most of the features requested in place and will improve their usability as I find time. I just added an important feature: the ability to flag specific data points for comparison.

For example, you can click the highest data points for CO2 levels and horizontal and vertical lines will mark the point in the same color as the graph that was clicked:

Then, if you rescale the x axis, say to zoom in on the Holocene, you can see the y values of the data points you flagged from 323 k and 414 k years ago:

As always, I continue to take requests for features. My next big change (I hope) will be allowing multiple views of the x-axis timeline, so you can directly compare the shape of graphs between different time periods. My data viewer is available here: Epica-Vostok viewer.

jg

Vostok icecore and Earth's orbit graphs

Almost two weeks ago, I had the honor of guest posting at Skeptical Science, sharing my latest illustration project, the Vostok Viewer, an interactive graphing tool that displays data from the Vostok icecore alongside calculations of Earth's orbit (data sources: Vostok; orbit; modern CO2).

My guest post: Skeptical Science: Ice data made cooler 

I received a lot of constructive feedback and have started adding the suggested features. I've exposed my version 2 and qualified it as beta (in progress), as I have a couple known programming bugs:

A cautious user (someone not trying to evoke a failure) will have the benefit of displaying graphs, adjusting their scale, and showing and hiding labels for an informative yet uncluttered display.

My known bugs are:
1. Displaying the modern CO2 graph while viewing a pre-modern time era will create a later failure where orbit graphs fail to update when changing time periods.
2. The graph labels may fail to align with their graphs when time periods are changed.
jg

Palaeoclimate graphs from Vostok Ice Core and Orbit Calculations

I have envied the climate charts I've seen in Wikipedia and in science journals showing temperatures, CO2, insolation, and orbit parameters over the past million years, so I decided to create my own viewer: Vostok Viewer

I've taken the data from these sources:

• Petit, J.R., et al., 2001,  Vostok Ice Core Data for 420,000 Years, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2001-076. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.
• Astronomical Solutions for Earth Paleoclimates. A&A 428, 261-285 (2004), DOI: 10.1051/0004-6361:20041335; Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A.C.M., Levrard, B. : 2004, A long term numerical solution for the insolation quantities of the Earth.

and created this:
 

...which is a Flash-based viewer that allows you to see graphs of data from these sources and to zoom in on specific periods, such as the Eemian:

My program is crude at this time. I plan to add more features for controlling the appearance of the graphs as well as flexible views of the timeline (so a user can focus on any period rather than those I've configured). And of course, I'll add other data sets, but for now I hope to iron out the features using the data I have.

I started this project when I wanted to see if observations I was making about the Eemian held up for other interglacials. I saw a strong correlation between summer insolation at 65 degrees N and the onset of interglacial temperatures. This correlation was consistent with what I've read from science journals. However, from my Vostok Viewer, I'm observing that the correlation isn't as visually striking for the interglacials at 240 kya and 325 kya:

The green line in the above graphs is June insolation at 65 degrees N. For the onset of the Holocene and Eemian, you can see that the green curve corresponds to rises in temperature (yellow) and CO2 (lavender), but in the earlier interglacials, the solar forcing peaks before the peak in temperature and CO2.

This discrepancy invites more study from me. Are there see-saw effects that delayed warming in Antarctica or are there margins of error in the dating of the CO2 and temperature values? Is it time for me to open the book on more sophisticated data analysis? I'm sure the climatologists know. Here, I'm trying to do my homework before asking.

jg

Earth, Orbit, and Climate for Sierra Club, 23 Sept

Thurs, 23 Sept., 7:00 pm at the Rancho California Water District building in Temecula, Ca, I'll be presenting the latest version of my talk on Earth, Orbit and Climate. In Earth, Orbit, and Climate, I share what I've learned in the past few years about the astronomical foundation of climatology, and specifically, the roll of Earth's orbit in governing climate over millennial time scales. I also discuss greenhouse gases and Earth's carbon cycle.

I draw heavily on the following resources:

• Trenberth, Fasullo, Kiehl: Earth's Global Energy Budget
• Pierre-Humbert, Principles of Planetary Climate
• Laskar, Robutel, Joutel, Castineau, Correia, Levrard: 2004, A long term numerical solution for insolation quantities of Earth (Astronomical solutions for Earth Paleaoclimates)
• Petit et al., 2001, Vostok Ico Core Data for 420,000 Years (http://www.ncdc.noaa.gov/paleo/icecore/antarctica/vostok/vostok_co2.html and http://www.ncdc.noaa.gov/paleo/icecore/antarctica/vostok/vostok_isotope.html)
• Kopp et al (Nature 17 Dec 2009)
• Hanson, Storms of My Grandchildren
• NASA, Jet Propulsion Laboratory (source of Earth, Venus, and Mars images used in illustrations)

My revised presention will be online within the next few weeks (current version: Earth, Orbit and Climate). My new version will remove the section on the solar system, which was pretty weak (on my part; no reflection on my source). The most exciting change is that I've added a section on the Eemian interglacial in which I've used astronomical solutions, CO2 levels, and temperature data from the above references to illustrate the Milankovich theory of climate. Below is an illustration from the presentation.

Within a few weeks I hope to update the online version and provide elaboration here for the fun of sharing as well as exposing my work for educational criticism.

jg

Eemian orbital forcing

Astronomical solutions for paleoclimates generates Earth's orbital parameters (eccentricity, tilt, climatic precession, and insolation) over a span of 50 million years in the past to 20 million years in the future. One of my slow learning projects has to been to use the output from this program to create illustrations of orbital configurations at key climatic transitions, such as the Eemian interglacial. When graphed, data of orbital parameters often look like this:

(Diagram redrawn from Wikipedia and IPCC 4th Assessment Report)

For a scientist, this is useful, but not being a scientist I looked for a display that I would find inituitive and useful for explaining what I'm learning to others. I'm not going for precision, but rather, for an illustration that can show the change and show when some orbit parameters would have a collective warming or cooling influence. For example, the following contains my exaggeration of orbit eccentricity and tilt:

Tilt is a stretching of the 4-season ring so that the points of summer and winter solstice are elongated. Elongated means tilt is high, making summers and winters more extreme. Eccentricity is the blue elipse, which is exaggerated in relation to Earth's real orbit so that one can easily see when a solstice occurs near perihelion or near aphelion, and then intuitively recognize that this can make a northern hemisphere summer or winter on top of tilt milder (winter near perihelion or summer near aphelion) or more extreme (winter near aphelion; summer near perihelion).

So here are three orbits from the Eemian, starting from right to left, 30,000, 27,000, and 24,000 years ago:

I think I captured the orbits correctly (according to my analogy) in the top half of the diagram. The bottom half is wrong, but I'm keeping it as a puzzle for me to ponder how to fix (the right Earth should be paired with the left orbit; and the left, with the right, but I still want the tilt oriented to the sun).

Using Astronomical Solutions, I gathered the mean monthly insolation for June at 60 degrees North latitude. I chose 1000-year intervals to minimize the numbers I have to chart. I included eccentricity, tilt, and climatic precession. Also, I generated the insolation for 60 degrees South latitude during December, so I could compare the Northern summer's solstice to the Southern summer's solstice. One can see a big difference in insolation as a result of the two summers occuring at opposite ends of Earth's orbit. I also throw in some Holocene values to compare astronomical forcing of the Eemian to today.

Next, I hope to get some data on CO2 increases from warming (which in turn would warm the Eemian further) and add some illustrations of possible arctic and ocean feedbacks that will have added to warming or would have contributed to the rise of atmospheric CO2.

jg

Hammock Earth; comparing sea levels of the Eemian to the Holocene

I just finished reading Kopp et al's "Probablistic assessment of sea level during the last interglacial stage" and the excellent News and Views summary by Clark and Huybers. Both articles appeared in the 17 Dec. 09 issue of Nature. The illustration on the left is my greatly simplified analogy of Kopp et al's effort to assess how the redistribution of mass from icesheets as water during the Eemian affects proxy measurements of sea level. Just as pillows of ice at each end of a hammock would change the hammock's shape, so too would icesheets and their loss affect the shape of the global ocean basin. If "hammock earth" becomes a usable term, I expect full credit or ridicule for coining it.

Below is a summary of their work, comparing their assessment of sea level to today's. Both articles compared the warmer Eemian temperatures to comparable temperature increases expected from current and expected increases of greenhouse gases. Missing from my diagram is a clarification that sea levels rose at perhaps 65-90 cm per century to the estimated 6-9 meters above current sea level.

(update 5/6/10: revised sketch)

The warmer Eemian climate is linked to greater northern hemisphere insolation as a result of an orbit with greater eccentricity and precession that placed the northern hemisphere solstice close to perihelion. Below, I'm comparing Earth's orbit at the Eemian with Earth's current orbit. These diagrams are for illustration; they are not to scale. I created them using my orbit viewer.

A potential sea level rise of up to 9 meters, suggested by Kopp et al, is disturbing, especially because the author's don't rule out periods of a higher rate of change that the 62-90 cm per century. For me, the observation that CO2 levels didn't rise beyond the Holocene's pre-industrial levels is intriguing. CO2 and methane from a warming biosphere is part of a worst case global warming scenario. I wonder if the Eemian shows that we have a 2-4 C grace period before this feedback kicks in.

jg

On Reading Hansen's Storms of My Grandchildren

Before reading Storms of my Grandchildren, I had confidently told a few friends that a Venus style run-away greenhouse effect was not a realistic expectation from even the most excessive fossil fuel use. Hanson's book was a delightful read, in that I recognized a lot of the scientific literature he is drawing on, but he made connections between stellar evolution, paleo-climate reconstructions, and unknowns about the endurance and long-term reliability of carbon sinks that disturb him. If these variables disturb James Hansen, I felt it was worth a picture. I've tried to add a few other elements to the picture, including a redrawn CO2 level from Richard Alley's recent presentation an the AGU: CO2, The Biggest Control Knob.