In addition to the production version of its plug-in hybrid sedan, the Fisker Karma, Fisker Automotive plans to show a concept car called the Fisker Karma S (for “Sunset”) at the North American International Auto Show in Detroit next month. What’s unusual about the Sunset is not that it’s a hybrid — the show will feature a gang of those from big automakers this year — but that it appears to be a convertible (suggested by the missing B-pillar).

If the concept car makes it to real-world production, it could help Fisker forge a distinct path in the green car market — one that leads to a small luxury niche, rather than mass-market scale. According to the most recent available data from auto industry research firm R.L. Polk & Co., convertibles make up only about 2 percent of light-vehicle registrations. For most automakers, they serve more as halo vehicles (designed to boost brand image and lure people into showrooms) for automakers than real sales drivers. For a startup like Fisker, sticking to niche markets could be a smart post-recession bet, as becoming large enough to mass produce vehicles has proven capital intensive enough to cause competitors like Tesla to reconsider broader more mass market plans.

But convertibles themselves aren’t necessarily a solid bet. Polk analyst Lonnie Miller told BusinessWeek back in the spring, when the previous year’s slumping demand appeared to be carrying over into 2008, convertibles fare worse than most in a gloomy economic climate. Convertible registrations dropped by nearly 9 percent in 2007, compared with only a 2.5 percent drop in light vehicle sales for the same period. “We joke that a convertible is a midlife crisis car; it’s a feel-good emotional car,” she said. “There are all these psychological factors, and if people are uncertain, it falls to the bottom of the priority list when it comes to transportation needs.” So while the Karma went from concept to production in a year flat, rollout of the Sunset may best be delayed until the clouds of recession clear.

Brits Develop Carbon-Eating Cement: A new kind of cement based on magnesium silicates requires much less heating than the conventional stuff (which accounts for 5 percent of global carbon emissions) and absorbs large amounts of CO2 as it hardens. — The Guardian

Gimme a $2-a-Gallon Gas Tax, Says…Texas Oil Man?!: “There’s a reason that everybody in Europe drives roller skates and here we drive SUVs. It’s because Europe has a huge tax on gasoline.” — Fortune

Record Insurance Payouts, Courtesy of Climate Change: Adjusted for inflation, 2008 was the third most expensive year on record for the German reinsurer Munich Re. The company is now calling for an international plan to halve emissions by 2050. — NYT’s Green Inc.

2009 Forecast: Hot Hot Hot: UK climate scientists expect the 2009 to be among the five warmest years on record, indicating a rapid return of global temperature to a long-term warming trend and an increasing probability of record temperatures after 2009. — Green Car Congress

Climate Change Off Hook for Neanderthals’ Doom: Recent analysis of late-Pleistocene hominid habitation delivers a solid blow to the popular hypothesis that climate change did them in. Now it looks like they just couldn’t compete with modern humans. — Wired Science

Car buyers in California could be getting a different kind of sticker shock in the new year. Starting Jan. 1, every 2009 model year and newer car sold in California will be required to carry a label that ranks, in addition to the existing requisite smog ratings, the vehicle’s global warming impact.

California’s Air Resources Board said the new label will have two scores on a scale of 1-10 — one for smog and the other for global warming — with the average new car scoring five on both. The higher the score, the more environmentally friendly the car.

The Global Warming Score is based on the vehicle’s greenhouse gas emissions, with 1 being 520 CO2-equivalent grams per mile and up, and 10 being less than 200. The board said the scores are adjusted to reflect the contribution of emissions from the production and distribution of the fuel used.

The Smog Score, which started showing up on new cars sold in California with the 1998 models, ranks each vehicle’s pollutant levels of non-methane organic gases and nitrogen oxides relative to other vehicles within that model year.

Even if you’re not in California, you can take advantage of the new scoring system by surfing over to www.DriveClean.ca.gov, which offers up information from the Air Resources Board on the cleanest and most efficient cars available. You can’t search by Global Warming Score yet, but a number of small, low-speed electric vehicles come out on top of the Smog Score rankings, with highway-speed cars led by Tesla’s electric Roadster and the Toyota Prius hybrid.

The new Global Warming Score was put into effect as the result of Assembly Bill 1229 that was signed into law in 2005.