The Weekly Carboholic: "heat island" effect is minimal

Posted on September 10, 2008

2


carboholic

One of the more common arguments you hear from global heating deniers and skeptics is that the urban heat island effect is causing global temperature measurements to look a lot hotter than they actually are. This is such a powerful argument because there is some truth to it – when you plop down a new road or build a town around what used to be a rural National Weather Service temperature monitoring station, there’s going to be a major uptick in the temperature that station measures. Skeptics like Anthony Watts of Wattsupwiththat.wordpress.com have spent a great deal of time documenting situations where new roads, new construction, even the addition of an asphalt walkway to a gas grill could be responsible for spurious temperature readings out of weather stations. However, the argument that global heating is all a misunderstanding of the urban heat island effect took a hit recently with the release of a new study that finds temperatures measured in established cities trend nearly identically to rural temperatures.

The key word there is “established”. According to paper co-author David Lister, if a city has been around long enough, and if temperature measurements have been taken in the urban area long enough, then you can measure both the average temperature difference and the trend of the the local temperature. And when Lister and his colleagues analyzed both the temperature average and trend over cities, the found that if a city had been measuring data for a long time, then the the urban heat island effect was almost entirely negated. Here’s how that works.

Let’s say you’ve got a thermometer outside your house sitting above an asphalt road. You know it’ll be hotter than a thermometer a mile away next to a pond – that’s the urban heat island effect. But if you take measurements using the same thermometers and at the same time for years, you’ll find that the trend (how much each thermometer goes up and/or down over time) is roughly equal for each thermometer. The one outside your house may be two degrees hotter all the time than the one by the pond, but because it’s hotter all the time, the difference in the temperature of the thermometer outside your house from one year to the next will be pretty much the same as the difference in the temperature of the thermometer at the pond from one year to the next.

Or, to use a different example, if you’re jumping up 10 feet above a trampoline, you’re still going to be 10 feet in the air over the trampoline even if you put the trampoline up on the roof instead of on the ground – you’re jumping jumping up and down just as high even though the trampoline is higher in the air. The trampoline on the roof is like the thermometer on your house over asphalt while the trampoline in the ground is like the thermometer by the pond.

What this means is that climatologists can be confident in using urban temperature data for monitoring stations in established cities so long as the monitoring station itself has been stable (no new asphalt walkways to grills nearby). Cities like London, Vienna, New York, Tokyo, etc. where there are decades if not centuries of temperature data are just as good thermometers of global heating as rural locations.

However, in situations where cities pop up around monitoring stations or where new monitoring stations are installed, extreme care must be taken in order to get accurate temperature data. After all, you don’t want to be measuring how high someone’s jumping off a trampoline on the ground only to have the trampoline moved atop the roof without your noticing, because that would mess with your measurements. It appears that Lister’s group crunched some data on Chinese urban temperature monitoring and found that only about 60% of measured temperature increase was actual trend as opposed to urban heat island effect.

All in all, it sounds like an excellent paper.

———-

A new study into the ice sheets that once covered North America suggests that Greenland may melt dramatically faster than the IPCC or even most climatologists expect. The study, reported in Nature News, suggests that the entire North American ice cap (the Laurentide ice sheet, or LIS) melted over the course of about 1,000 years, producing enough meltwater to raise ocean levels by 0.7 to 1.3 meter per century. According to the article, this was likely because the land mass of North America warmed fast enough to drive the ice sheet back.

This applies to Greenland because it suggests that, once the ice is gone from the margins of the island, the warming land will warm the ice cap and melt it quickly, perhaps within just a few centuries. This is a much faster pace than scientists previously expected, and there will no doubt be some disagreement about the accuracy of this new study as a result. But if it’s true, then coastal regions should expect a great deal more sea level rise due to Greenland’s melt than the last IPCC estimate.

The article also pointed out that the scientists did something that many global heating deniers do not – they verified their conclusions. The scientists initially determined the rate of the LIS collapse using “radiocarbon dates of organic matter and marine shells, cosmogenic dates from the surface of boulders, and the composition of isotopes in marine sediment cores”, but then the scientists also used a state-of-the art climate model to see if its results would bear out the paleoclimate data.

It did, providing yet another independent accuracy check on climate modeling, or at least the climate model(s) that was used by the scientists involved in this study.

———-

One of the strangest climate articles I’ve read yet came across my LCD screen last week. According to the Times Online, a classified group of scientists code-named “Jason” developed a rudimentary climate model back in the late 1970s that predicted global heating remarkably similar to what the IPCC is predicting today. This was during the “we’re headed into another ice age” period, by the way.

According to the article, what ultimately turned the Jason group’s conclusions around was the election of Ronald Reagan as President. Reagan apparently didn’t like the conclusions of the Jasons or of the climate scientists of the National Academy of Sciences (which had agreed with the Jasons conclusions in a report headed by MIT professor Jule Charney), so Reagan commissioned a third study by Bill Nierenberg that ultimately gave Reagan what he wanted to hear:

Overall, the synopsis emphasized the positive effects of climate change over the negative, the uncertainty surrounding predictions of future change rather than the emerging consensus and the low end of harmful impact estimates rather than the high end. Faced with this rather benign scenario, adaptation was the key….

But this was only the beginning of his involvement in what eventually became a movement of global warming sceptics. A year after his report came out he became a co-founder of the George C Marshall Institute, one of the leading think tanks that would go on to challenge almost every aspect of the scientific consensus on climate change. Nierenberg hardened his position. He began to argue not just that global warming wasn’t a problem, but also that it wasn’t happening at all. There was no systematic warming trend, the climate was simply going through its normal, natural fluctuations.

And thus began the global heating denialist industry we’re still fighting today. Just think how much different things might be today had Reagan not been the original decider, and had decided to ignore science in favor of faith thirty years ago….

———-

There’s some good news about global heating too, though. According to Reuters, case of plague are likely to fall in the U.S. because the climate will be too hot and too dry to support the fleas and rats that host and vector the disease.

Great news for the desert southwest and its fringes. Too bad that plague cases are expected to go up in central Asia, where the climate is expected to get wetter. Talk about a mixed blessing.

———-

According to the Washington Post, California bill SB375 may be the first-in-the-nation urban planning law designed specifically to reduce greenhouse gas emissions. The bill gives top priority for federal transportation and development dollars throughout the state to high density urban centers in a bid to drastically cut down on driving. And while no new transportation projects would be turned down because they didn’t comply with the new law, 100% of transportation subsidies would go to complying projects by 2012.

If this bill is signed by Governor Schwarzenegger as it’s expected to be, then California will become the first state to consciously choose to focus people into high density urban living and out of suburban tract homes. If other states, or even the federal government under a new president, were to follow suit, this could be the start of a major cultural transformation in the United States.

And that could be just what the U.S. needs to address global heating.

Advertisements
Posted in: Uncategorized