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Ice Shelf Instability

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Guest contribution from Mauri S. Pelto

Ice shelves are floating platforms of ice fed by mountain glaciers and ice sheets flowing from the land onto the ocean. The ice flows from the grounding line where it becomes floating to the seaward front, where icebergs calve. For a typical glacier when the climate warms the glacier merely retreats, reducing its low elevation, high melting area by increasing its mean elevation. An ice shelf is nearly flat and cannot retreat in this fashion. Ice shelves cannot persist unless the entire ice shelf is an accumulation zone, where snowpack does not completely melt even in the summer.


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Butterflies, tornadoes and climate modelling

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Ed Lorenz hiking Many of you will have seen the obituaries (MIT, NYT) for Ed Lorenz, who died a short time ago. Lorenz is most famous scientifically for discovering the exquisite sensitivity to initial conditions (i.e. chaos) in a simple model of fluid convection, which serves as an archetype for the weather prediction problem. He is most famous outside science for the ‘The Butterfly Effect’ described in his 1972 paper “Predictability: Does the Flap of a Butterfly’s Wings in Brazil Set Off a Tornado in Texas?”. Lorenz’s contributions to both atmospheric science and the mathematics of dynamical systems were wide ranging and seminal. He also directly touched the lives of many of us here at RealClimate, and both his wisdom, and quiet personal charm will be sorely missed.

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Moulins, Calving Fronts and Greenland Outlet Glacier Acceleration

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Translations: (Español)

Guest Commentary by Mauri Pelto

The net loss in volume and hence sea level contribution of the Greenland Ice Sheet (GIS) has doubled in recent years from 90 to 220 cubic kilometers/year has been noted recently (Rignot and Kanagaratnam, 2007). The main cause of this increase is the acceleration of several large outlet glaciers. There has also been an alarming increase in the number of photographs of meltwater draining into a moulin somewhere on the GIS, often near Swiss Camp (35 km inland from the calving front). The story goes—warmer temperatures, more surface melting, more meltwater draining through moulins to glacier base, lubricating glacier bed, reducing friction, increasing velocity, and finally raising sea level. Examining this issue two years RealClimate suggested this was likely the correct story. A number of recent results suggest that we need to take another look at this story.

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Air Capture

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Translations: (Español)

Guest Commentary by Frank Zeman

[This is one of an occasional series on the science of mitigation/adaptation/geo-engineering that we hope to continue. Since this isn’t our core expertise, we’d especially appreciate balanced contributions from other scientists.]

One of the central challenges of controlling anthropogenic climate change is developing technologies that deal with emissions from small, dispersed sources such as automobiles and residential houses. Capturing these emissions is more difficult as they are too small to support infrastructure, such as pipelines, and may be mobile, as with cars. For these reasons, proposed solutions, such as switching to using hydrogen or electricity as a fuel, rely on the carbon-free generation of electricity or hydrogen. That implies that the fuel must be made either by renewable generation (wind, solar, geothermal etc.), nuclear or by facilities that capture the carbon dioxide and store it (CCS).

There is however an alternative that gets some occasional attention: Air Capture (for instance, here or here). The idea would be to let people emit the carbon dioxide at the source but then capture it directly from the atmosphere at a separate facility.

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The global cooling mole

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By John Fleck and William Connolley

To veterans of the Climate Wars, the old 1970s global cooling canard – “How can we believe climate scientists about global warming today when back in the 1970s they told us an ice age was imminent?” – must seem like a never-ending game of Whack-a-mole. One of us (WMC) has devoted years to whacking down the mole (see here, here and here, for example), while the other of us (JF) sees the mole pop up anew in his in box every time he quotes contemporary scientific views regarding climate change in his newspaper stories.

Una traducción está disponible aqui
Tłumaczenie na polski dostępne jest tutaj.

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Tropical cyclone history – part II: Paleotempestology still in its infancy

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Guest Commentary from Urs Neu

While analyzing tropical cyclone records is difficult enough (see ‘Tropical cylone history – part I’), it is even more challenging to reliably estimate hurricane activity back in time. Recently, Nature published an attempt to reconstruct past major hurricane activity back to 1730 (Nyberg et al. 2007). The authors concluded that the phase of enhanced hurricane activity since 1995 is not unusual compared to other periods of high hurricane activity in the record and thus appears to represent a recovery to normal hurricane activity. The paper was advertised in a press release put out by Nature and received broad media attention.

Although the approach outlined by the authors is interesting, the study contains in my view a number of problems, as outlined in a comment published in Nature today (Neu 2008):

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Tropical cyclone history – part I: How reliable are past hurricane records?

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Guest Commentary from Urs Neu

When discussing the influence of anthropogenic global warming on hurricane or tropical cyclone (TC) frequency and intensity (see e.g. here, here, and here), it is important to examine observed past trends. As with all climate variables, the hurricane record becomes increasingly uncertain when we go back in time. However, the hurricane record has some peculiarities: hurricanes are highly confined structures, so you have to be at the right place at the right time to observe them. Secondly, hurricanes spend most of their life in the open oceans, i.e. in regions where there are very few people and no fixed observations. This means that the reliability of the long-term hurricane record is dependent on who was measuring them, and how, at any given time. The implementation of new observation methods, for example, might have altered the quality of the record considerably. But how much? This crucial question has been widely discussed in the recent scientific literature (e.g. Chang and Guo 2007, Holland and Webster 2007, Kossin et al. 2007, Landsea 2007, Mann et al. 2007). Where do we stand at the moment? This post will concentrate on the North Atlantic, which has the longest record.

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Antarctica is Cold? Yeah, We Knew That

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Translations: (Español)

Guest commentary from Spencer Weart, science historian

Despite the recent announcement that the discharge from some Antarctic glaciers is accelerating, we often hear people remarking that parts of Antarctica are getting colder, and indeed the ice pack in the Southern Ocean around Antarctica has actually been getting bigger. Doesn’t this contradict the calculations that greenhouse gases are warming the globe? Not at all, because a cold Antarctica is just what calculations predict… and have predicted for the past quarter century.

It’s not just that Antarctica is covered with a gazillion tons of ice, although that certainly helps keep it cold. The ocean also plays a role, which is doubly important because of the way it has delayed the world’s recognition of global warming.

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What if you held a conference, and no (real) scientists came?

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Over the past days, many of us have received invitations to a conference called “The 2008 International Conference on Climate Change” in New York. At first sight this may look like a scientific conference – especially to those who are not familiar with the activities of the Heartland Institute, a front group for the fossil fuel industry that is sponsoring the conference. You may remember them. They were the promoters of the Avery and Singer “Unstoppable” tour and purveyors of disinformation about numerous topics such as the demise of Kilimanjaro’s ice cap.

A number of things reveal that this is no ordinary scientific meeting:

  • Normal scientific conferences have the goal of discussing ideas and data in order to advance scientific understanding. Not this one. The organisers are suprisingly open about this in their invitation letter to prospective speakers, which states:

    “The purpose of the conference is to generate international media attention to the fact that many scientists believe forecasts of rapid warming and catastrophic events are not supported by sound science, and that expensive campaigns to reduce greenhouse gas emissions are not necessary or cost-effective.”

    So this conference is not aimed at understanding, it is a PR event aimed at generating media reports. (The “official” conference goals presented to the general public on their website sound rather different, though – evidently these are already part of the PR campaign.)

  • At the regular scientific conferences we attend in our field, like the AGU conferences or many smaller ones, we do not get any honorarium for speaking – if we are lucky, we get some travel expenses paid or the conference fee waived, but often not even this. We attend such conferences not for personal financial gains but because we like to discuss science with other scientists. The Heartland Institute must have realized that this is not what drives the kind of people they are trying to attract as speakers: they are offering $1,000 to those willing to give a talk. This reminds us of the American Enterprise Institute last year offering a honorarium of $10,000 for articles by scientists disputing anthropogenic climate change. So this appear to be the current market prices for calling global warming into question: $1000 for a lecture and $10,000 for a written paper.
  • At regular scientific conferences, an independent scientific committee selects the talks. Here, the financial sponsors get to select their favorite speakers. The Heartland website is seeking sponsors and in return for the cash promises “input into the program regarding speakers and panel topics”. Easier than predicting future climate is therefore to predict who some of those speakers will be. We will be surprised if they do not include the many of the usual suspects e.g. Fred Singer, Pat Michaels, Richard Lindzen, Roy Spencer, and other such luminaries. (For those interested in scientists’ links to industry sponsors, use the search function on sites like sourcewatch.org or exxonsecrets.org.)
  • Heartland promises a free weekend at the Marriott Marquis in Manhattan, including travel costs, to all elected officials wanting to attend.

This is very nice hotel indeed. Our recommendation to those elected officials tempted by the offer: enjoy a great weekend in Manhattan at Heartland’s expense and don’t waste your time on tobacco-science lectures – you are highly unlikely to hear any real science there.