Category Archives: co2

Below the Antarctic circle

Icebergs in the Antarctic Strait (Margot, Jan 2011)

 

Antarctica in January 2011 was as breathtaking as I had imagined to be. Surreal landscapes of strangely sculpted icebergs drifting in seas, surrounded by snow covered mountains. Absolutely beautiful. And scary. The Antarctic peninsula is experiencing a frightening level of warming. The average temperature in this Western part of the continent has risen more than four times as fast as the average global temperature. Evidence can readily be found. Spectacular ice shelf break ups, like that of Larsen B, leave massive chunks of ice floating, and melting, in the coastal waters around Antarctica. Where the coastal ice shelf disappears, glacier flows are no longer held back and long tongues of land ice find their way towards the sea.

Iceberg in the South Atlantic, courtesy of my friend Story Musgrave (astronaut)

Why do these ice sheets break up? It is not because of weakening or melting of the ice sheet upper surface. West Antarctica is a collection of islands. They are covered by thick layers of land ice and in many places connected by ice shelves that stretch across the water. In many places, prevailing winds push relatively warm surface water to the ice shelves. Where this water touches the ice, the shelves thin. Eventually they develops cracks, weaken and breaks up.

As temperatures around the Antarctic Peninsula increase further, the combined effect of ice shelf break up and increased glacial flow towards the coastal region may contribute significantly to global sea level rise. How much? This is hard to predict, but the crew and the scientists aboard our ship have over the years seen dramatic changes in ice coverage.

Right now, the one creature that seems most affected by the change in the local temperature is the Adelie penguin, one of my favorite creatures. They don’t do very well in higher temperatures and are gradually being displaced by Gentoo and Chinstrap penguins. It may not seem all that important at the moment. The Adelies can move further South, and they are. But there is much more at stake. Sea level rise is one concern, but so is a change in carbon dioxide absorption by the Southern Sea, thought to be critical in global climate behavior, because of changing ice coverage. We do not know yet how much the ecosystem as a whole will be affected. But I would be surprised if it remained relatively unscathed with this strong and fast West Antarctic warming.

Someone who knows a lot about ice melt and changing glacial ice coverage is photographer James Balog. James started the Extreme Ice Survey. EIS is making the world’s most extensive ground-based photographic glacier study. Time-lapse video and photography reveal the ongoing retreat of glaciers and ice sheets due to temperature changes. EIS has installed 38 time-lapse cameras at 22 glaciers in Greenland, Iceland, Nepal, Alaska, and the Rocky Mountains and conducts annual repeat photography in Iceland, British Columbia, the Alps, and Bolivia. We were very lucky to have James on board with us.

The journey to Antarctica was amazing. So was the wake-up call.

The upside of the downturn

Interesting article today in the New York Times about a (small) silver lining in the current economic and climate gloom. Emissions have gone down a bit because of the economic downturn, but more importantly China is making more rapid progress towards the reduction of its carbon dioxide emissions, mostly through nuclear energy and wind.

Mighty interesting, those developments in China. Think SE needs to visit soon….

 

Science: special issue on Carbon Sequestration and Storage

Check out the latest Science magazine for its special issue on Carbon Sequestration and Storage. Steve Chu, Secretary of Energy, contributed to this issue as well.

 

Flying greener: sustainable aviation

As I type this I’m listening to my colleague Ilan Kroo, professor in Aerodynamics at Stanford University and a world renowned airplane designer. The topic of his lecture is Sustainable Aviation: Future Air Transportation and the Environment.
A few blogs ago I gave some current numbers on the efficiency of air travel vs car travel. A Boeing 737 with 75% occupancy gives about 80 miles/gallon for each passenger. This compares favorably to a car, but then, we would not drive across the Atlantic.
What is encouraging is that fuel efficiency has dramatically improved over the years and is expected to improve further. Current jets, such as the 767, use around 70% less fuel compared to the early jets, such as the 707-320. But, perhaps that is because these early jets were so bad! The next generation (787) will give about 20% improvement over the current (second) generation planes.
Aviation accounts for about a seventh of transport in terms of carbon emissions. With transport making up around a seventh of total green house gas emissions, this means that total carbon emissions from airtravel is about 3% of total. Sounds OK, but the effects of emissions at altitude are a fair bit higher. Looking at carbon calculators, one round trip San Francisco to Paris is about 15% of the emissions of an average US household per year (aye, this hurts when I think about my own air travel….).
What is troubling is that air travel is growing very fast. Growth is about 5-6% per year worldwide in passenger and cargo air travel, which could mean a three-fold increase in the next decades. So, it’s much worth while looking at ways to reduce emissions.

At the government level, the US, Europe (Clean Skies Initiative) and Canada are starting new initiatives. In Stanford’s AA department a new sustainable aviation program has also been started. It includes work on new concepts and technologies, as well as safely increasing air transportation system capacity, and monitoring of its environmental impact.

One example of an environmental impact, apart from green house gas emissions, is contrail formation in super-saturated and cold air. This can often be avoided, quite simply, by changing the cruise altitude by a few thousand feet. Contrails are of interest because, like the carbon dioxide emitted, they lead to a positive radiative forcing. This in itself is not a great measure of climate impact. In contrast to carbon dioxide or other particles, contrails do not stick around for hundreds of years. But, aircraft generally cruise in a narrow altitude band where control persistence conditions are most likely. So, although accurate estimation of the impact on global climate of contrails is rather challening and uncertain, it is probable that it has an impact.

Taking into account environmental impacts, the AA department has run optimization models. It is possible to adapt designs to minimize climate impacts, but then generally one pays penalties in terms of cost or travel time or both, for example. What is very encouraging is that the preliminary studies indicate that a relatively small reduction in speed with a 1-2% increase in costs can reduce climate impact by 50-70% (that is, if contrails really are important contributors to global warming). Uncertainties are however still high, but it’s really worth looking at this in more detail.

In terms of new technologies, Ilan offered various ideas. One is to look at alternative fuels. But hydrogen, for example, is not great as the energy density per volume is much lower than kerosene. Ethanol is also not ideal in terms of energy density. Gas-to-liquid synthetic jet fuels may be an option.
Another idea is to use aerial refueling so that airplanes do not have to carry all the fuel for the full flight. In other words, design airplanes to design, say, 3000 miles rather than 9000 miles and refuel along the way. The military has great expertise in aerial refueling and this could be utilized.
A really interesting idea is to fly airplanes in formation (like geese) which can lead to potentially large drag reductions.
The new 787 has more efficient engines which leads to a 20% improvement in fuel efficiency. New composite materials can lead to weight reductions, which in turn will lead to fuel efficiencies. Larger span wings supported by struts, gust load control and airplanes with tail in front, or blended wing bodies, are all ideas that can be and are being considered.

So, in summary there are large potential savings possible with optimized designs for low noise and low emissions with limited cost and/or utility changes. New technologies could improve things (much) more. All very positive.

This talk will be available on Stanford I-tunes shortly and I will include the link when it is available.