Archive for June, 2009

How Long Until Greenland Melts?

June 11, 2009 at 3:10 pm · Filed under Environment, Geopolitics ·Tagged , , , ,

It would take 7400 years to melt Greenland at currently observed ice melting rates, and many hundreds of years even with a non-linear increase in melting rates.

Numerous studies and direct observation show that Greenland’s ice sheet is melting, and the latest studies show that snowfall on Greenland is not sufficient to offset this loss. If the entirety of Greenland’s ice sheet were to melt, sea levels worldwide would rise by roughly 20 feet. This rise would severely damage or wipe out many of the world’s major cities, and accordingly the threat of catastrophic sea level increase is listed among the primary threats of global warming.

This brings to light an important question: how long do we have until Greenland’s ice sheet melts, or until its melting causes a significant amount of sea level rise?

Greenland’s ice sheet has a total volume of 2.6 million kilometers cubed, and according to a recent study, lost an average of 222 km cubed of ice in the last couple of years. In 2007, the year that Arctic ice cover set a new summertime minimum, 350 km cubed of ice was lost. Assuming this extreme rate continues, Greenland will be fully melted in 7400 years. Of course, ice melt rates are non-linear, and so this rate could increase considerably as temperatures rise.

Assume for a moment that the rate of ice melt rises by an order of magnitude (10x) beyond the 2007 record. 740 years of melting would still be required to melt all of Greenland, and even at that rate sea levels would rise only 2 feet by 2100! If the ice immediately begins melting at 100 times the record rate, then a real catastrophe would ensue, as sea levels would rise by the full twenty feet before the end of the century.

What would it take to trigger a catastrophic increase in Greenland’s ice melt rate? Unfortunately, this isn’t yet well understood, with some research showing that Greenland’s ice sheet could tolerate significantly higher temperatures. This is based in part on research showing that during the last interglacial period, 125,000 years ago, about half of the Greenland ice sheet persisted despite temperatures 5C higher than today. It’s a good idea to keep this and the melt rate calculations in mind when weighing the threat of AGW-induced sea level rise against potential solutions.

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The Hidden Trucking Industry Subsidy

June 2, 2009 at 7:51 pm · Filed under Business, Economics, Policy

Freight trucks cause 99% of wear-and-tear on US roads, but only pay for 35% of the maintenance. This $60B subsidy causes extra congestion and pollution, and taxpayers pay the bill.

It seems obvious that the heavier the vehicle, the more damage it does to roads over time. A 40,000 pound big rig probably does a bit more damage than your average 3500 pound consumer vehicle, right? It turns out that vehicle road damage doesn’t rise linearly with weight. Road damage rises with the fourth power of weight, and this means that a 40,000 pound truck does roughly 10,000 times more damage to roadways than the average car [1]!

In other words, one fully loaded 18-wheeler does the same damage to a road as 9600 cars. According to the American Trucking Associations (ATA), the trucking industry represents 11% of all vehicles on the road in the US, while paying 35% of all highway taxes. But if trucks represent 11% of vehicles, their heavy loads cause them to do 99% of all road damage! [2] The trucking industry paid $35 Billion in highway taxes in 2005, according to the ATA. Since most of the $100 Billion in highway taxes paid goes to maintenance (and US infrastructure maintenance is far behind), this implies that the trucking industry receives a $60 Billion annual subsidy from other drivers.

What are the negative effects of this subsidy? Since the trucking industry doesn’t pay the true cost of its road usage, it benefits relative to rail and other forms of transport. Freight rail lines are privately owned and maintained in the US, so they don’t receive a similar subsidy. As a result, more truck traffic ends up on highways than the market would dictate, leaving the taxpayers poorer, the air dirtier, and the roads more congested.

[1] Here’s some information on US pavement equations, including the statement of the fourth power law. Here’s another statement of the same, which also shows that on weaker surfaces, damage rises with the 6th power of the load.

[2] In order to calculate the damage done by trucks versus other vehicles, let’s assume that a fully loaded truck does the same damage to the roadway as 9600 cars, as mentioned above. In that case, then 11%, or 0.11 * 9600 = 1056. This is a measure of total damage done by truck traffic. Meanwhile, car traffic does 89% * 1 or 0.89 in damage. So the total damage is 1056 + 0.89 or 1056.89, of which 1056, or 99.9%, is done by trucks.

Perhaps half of all trucks are actually traveling empty. If an empty truck weighs 20,000 pounds, then it puts 4000 pounds onto each of its five axles, versus 2000 pounds on each axle for a car. The truck will do 2^4 more damage than the car, or 16 times more damage. So let’s add the totals back up: 5.5% * 9600 + 5.5% * 16 = 529. 529 / 529.89 = 99%. In fact, even if all big rigs in the US traveled empty, they would still do two-thirds of all damage to US roads!

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