Posts Made By: Jason Cosford

Now that's what I'm talking about!

A clean and renewable way to generate hydrogen that can then be used to power fuel cells. Certainly, there are issues to work out but at least we are collectively pursing these energy alternatives.

Jim Babcock said:

In the 70's it was predicted that we would be heading into an ice age instead of a warmer planet. Do we now know if the observations and predictions at that time was a result of either Global Dimming or the Asian Brown Clouds? I understand that we were not aware of these phenomena back then. Global Warming had not taken hold yet, but we had been pumping out particulates.

I want a crack at this one. In addition to Robert's response, there is another reason why global cooling received some media attention in the '70s and it reads like a history of understanding glacial-interglacial cycles. Although not the first, Milankovitch predicted that glaciations were caused by orbital dynamics. We can discuss this more, but I think most people know the Milankovitch cycles. The problem was that it was difficult to test because geologists had not refined dating techniques well enough to sufficiently resolve the chronology of glaciations. In the 1950s a fellow from the University of Chicago, named Caesar Emiliani, showed that the d18O composition of foraminifera in ocean cores recorded a very detailed history of glaciations - more so than what was possible on land because glacial deposits are eroded by subsequent glacial advances. Anyway, while Emiliani correctly speculated on his isotopic curve, the chronology was insufficient because 14C dating can only go back about 50000 years. In 1973 a paper was published by Shackleton and Opdyke that showed a magnetic reversal in the marine cores that could be accurately dated to 730,000 years. Using the new chronology of the marine cores, Hayes et al (1976) published a seminal paper where they demonstrated that the marine record exhibited cycles that matched those predicted by Milankovitch. Thus orbital dynamics were interpreted as the "pacemaker" of the ice ages.

Okay, so, how does this relate to the whole global cooling swish of the '70s? Well, because glaciations were paced by orbital dynamics, another glaciation was sure to occur during the next favorable orbital configuration - though the fact that this was thousands of years away was ignored by the popular press.

That global warming exists, there is no doubt. But whether the cause is human consumption of fossil fuels or a natural cycle, has not been adequately answered, in my opinion.

The drivers of climate change, both natural and anthropogenic, can be summed and compared to the observed rise in global temperature. When all of the natural drivers are summed, and yes there are error bars associated with these, the result is a rise in temperature that is less than what is observed. When the natural drivers are added along with the radiative forcing of anthropogenic CO2, the predicted temperature matches, within error, the observed record. What this means is that there are natural drivers, but anthropogenic CO2 is contributing to global warming. The issue should not be polarized yet we often hear one side argue that the warming is entirely a natural cycle and others that it is entirely our fault. The climate system is more complex than that.

Glaciers formed and covered most of North America and receeded without any human intervention several times in the last millinum. We need to understand that fact in relation to what is happening now with human intervention. The answer is not yet clear to me.

The first sentence is wrong. The vast ice sheets that covered North America advance and retreat on orbital time-scales and not over the last 1000 years. In particular, there is a 100,000 year cyclicity. There are also ~21ka and ~41ka cycles. The driver of these cycles is orbital dynamics (precession of the equinoxes, obliquity (tilt) of the axis, and orbital eccentricity. The last ice sheet that covered North America reached a maximum ice volume around ~17,000-21,000 years ago and retreated around ~10,000 years ago. This period since ~10 ka is called the Holocene and is a period of relative climate stability that allowed human civilization to flourish. During the Holocene, particularly the late Holocene, smaller mountain glaciers have shown episodes of advance and retreat, but nothing like the great ice sheets. The cause of these shorter period fluctuations is not as well known, but there are both celestial and terrestrial drivers that contributed.

Perhaps the cycle of volcanic activity was responsible for the formation and recession of the glaciers. Is the volcano of human consumption equivalent to that of mother earth? Dunno.

NO NO NO!!! I knew we would be talking volcanoes again. The USGS showed that annual CO2 emissions from all volcanic and geologic CO2 sources is 130-230 million tonnes. Humans emit a staggering 27 billion tonnes. That means we emit ~150X more than volcanoes. Here is a USGS website to read: http://volcanoes.usgs.gov/Hazards/What/VolGas/volgas.html

Doug,

Did you just use NASA and GISS data to defend an anti-global warming position?
Both have firmly stated that GHGs have contributed to the observed rise in global temps.

I had never heard of Jennifer Marohasy, so I looked up her blog.
Yikes. I also like the post on how arctic sea ice refuses to melt this summer.
Maybe she doesn't read the BBC http://news.bbc.co.uk/2/hi/science/nature/7585645.stm

Reposition fantasy as "fact" and dismiss fact as "fantasy". She must know Carl Rove, no? (Sorry, I'll keep the snarky political commentary for the politics forum )

No one can say with certainty that a full-blown ice age is, or is not, occurring in the imminent future.

To this comment, I would like to reply. The variability associated with sunspots over the 11-year cycle, or even those at 22, 88, 210, etc. are insufficient to trigger a glaciation. The terminology here may seem like semantics, but as a geologist, these are important in identifying the driving mechanisms. We are in an ice age. Over the course of geological history the Earth has shifted from a state of "ice house" to "hot house" on multimillion-year time-scales and relate to major tectonic-scale mechanisms. The current ice age began in the late Cenozoic and these conditions remain. Within this period there have been multiple glaciations and interglaciations, which exhibited a ~40ka cyclicity prior to ~800ka years ago and a ~100ka cyclicity today. The pattern of glaciations and interglaciations is strongly controlled by orbital dynamics as described by the Milankovitch Theory. Because these are physical motions that are quantifiable, it is possible to use the equations to predict the timing of the orbital configuration necessary to trigger the next ice age (it has been done and we are millennia away). Moving to even shorter time-scales, within a glaciation or interglaciation, there are millennial- to decadal-scale flucuations. This variability relates to both solar and terrestrial/oceanic mechanisms. The Little Ice Age is within this time-scale of climatic variability. On these scales, solar variability does impact global climate. Predicting the next Little Ice Age is not an easy task, however, there are ways of looking at the records to decipher periodic variability. The geological record of glacial moraines has shown that during the Holocene glaciers fluctuated with cycles of 2500 and 1500 years. The most recent manifestation of this cyclicity was the Little Ice Age and it appears to be related to a prolonged absence of sun spots. The absence of sunspots on any given year within the 11-year cycle is not cause to buy a new parka.

Let the markets decide who drinks. What, I can't buy water? That's un-American.

Andreas Saldivar said:

This is an interesting web site. You can look at the ice pack in both the arctic and the antarctic since 1979. While there has been some melting in the arctic, which the media tells you about over and over again, they don't seem to say what's happening in the antarctic. Look for your self. The data from the antarctic is probably what caused the term global warming to migrate to climate change.

Andeas

http://nsidc.org/cgi-bin/bist/bist.pl?annot=1&legend=1&scale=100&tab_cols=2&tab_rows=2&config=seaice_index&submit=Refresh&mo0=07&hemis0=S&img0=extn&mo1=07&hemis1=S&img1=conc&year0=2008&year1=1980&.cgifields=no_panel

I guess if you relied on the media then this would come as a surprise. For scientists, however, it is exactly as climate models predicted more than twenty years ago:
http://www.realclimate.org/index.php/archives/2008/02/antarctica-is-cold/

Andreas Saldivar said:

Here is a paper on recent, geologically speaking, climate changes.

http://www.esd.ornl.gov/projects/qen/transit.html

A little research turns up a lot of info like this. I learned stuff like this 20+ years ago when I got my geology degree.

Andreas

Andreas,

As a fellow geologist, I have to point out basic questions about time and process. Geology is all about time-scale and the processes that operate over tectonic time-scales differ from those that operate over centennial, decadal, or annual time-scales. The abrupt climate change during the last glaciation are well known, but the boundary conditions that existed at the time are entirely different from those today. In fact, as the famous geologist Wallace Broecker points out, the amplitude of these fluctuations reflect amplification of the boundary conditions. This fourm is filled with people well-versed in science, including geologists and climatologists, that fully understand that the climate system can fluctuate abruptly from natural processes. So let's look at the modern. When the natural driving mechanisms today are summed, the predicted increase in global temperature is less than that observed. However, when the foring of anthropogenic CO2 is added, the predicted rise in global temperature matches (within error) the observed temperature rise. Yes, abrupt climate change occurred natually in the past, but the driving mechanisms of the Younger Dryas, Dansgaard-Oeschger Events, Heinrich Events, etc. differ from those of today.

Andreas Saldivar said:

One large, but not often discussed, factor the drives the climate is the positions of the continents. It is thought that the Pliestocene ice age began when volcanic activity in present day Panama closed the isthmus of Panama. This caused a change in the ocean currents cutting off a heat source for the higher latitudes.

The Antarctic would not be so cold if Antartica was not there as the oceans are much better heat sinks than land. Land surrounding the Arctic keeps it colder than if it were more open.

The ulitmate global cooling theory is Snowball Earth. It theorizes that the Earth was covered with ice from pole to pole. Recent research indicates that it was more likely Slushball Earth. Either way though it would not be possible with out the continents position equatorially.

I have read and I saw this on a history channel show that because of the present day continental positions that the current warming would only delay the onset of the next ice age by 200 years.

Any thoughts?

Andreas

The position of the continents and tectonic processes do have a profound impact on climate, but operate on such lengthy timescales that they have little relevance to the 20th century warming trend and to predictions of climatic conditions over the next 200 years. Climatic deterioration during the Holocene can be attributed to several tectonic processes. The closing of the Isthmus of Panama, opening of the Magellan Strait, etc. Another critical factor was the Himalayan orogeny and the uplift of the Tibetan Plateau. Few problems in geology are as difficult to solve as paleoaltimetry, but the phases of uplift of the Tibetan Plateau certainly impacted Cenozoic climate. Click here to the publications page of Maureen Raymo: http://www.moraymo.us/climate_publications.php She has contributed a lot on the topic. If you don't have time to read them all, be sure to read through this one: http://www.moraymo.us/1992_Raymo_Nature.pdf


Over shorter timescales, like glacial-interglacial transitions ~100ka, orbital processes dominate the climatic signal. In particular the Milankovitch cycles. Without a rehash of theory, I simply point out that glaciations over the last 800ka years tend to last about 100ka separated by interglaciations of ~10ka. The current period we now live in, the Holocene, is an interglacial period that has lasted ~10ka. This has led some to predict the onset of full glacial conditions in the near geological future. But, hold on. When orbital dynamics are worked out for the future, it turns out that the insolation balance would not be suitable for another glaciation for millennia: http://www.sciencemag.org/cgi/content/summary/297/5585/1287 and the peak of the next glaciation should occur around 80000 years from now. All of this, of course, does not take into account anthropogenic CO2 emissions. University of Virgina prof William Ruddiman argues that the next glaciation would have already begun had it not been for human activities: http://www.personal.kent.edu/~jortiz/paleoceanography/ruddiman+al_qsr_05.pdf

Anyway, I guess my point is that, no, I don't think the current continental configuration will delay the next glaciation by 200 years.