Katie Fehlinger has the second part of her interview with Dr. William Gray in this week's edition of Headline: Earth. In this week's segment, Dr. Gray talks about why he doesn't trust computer climate models and his own climate theory. This is the theory that RealClimate has criticized. Watch Dr. Gray, read RealClimate and make up your own mind.

In this week's edition of Headline: Earth, Katie Fehlinger's climate change headlines included a reference to a new study released by NASA and the Columbia University Earth Insitute. This study, lead by Dr. James Hansen, concludes that the Earth's climate is approaching a dangerous tipping point. A tipping point is a threshold at which moderate temperature change is dramatically amplified by feedback mechanisms. One of my first entries on this blog talked about the potential positive feedback produced by the loss of snow and ice cover in the Arctic.

This study concludes that increased warming of only about 1° C (1.8° F) above 2000 levels is likely to be dangerous. "According to study co-author Makiko Sato of Columbia's Earth Institute, 'the temperature limit implies that CO₂ exceeding 450 ppm is almost surely dangerous, and the ceiling may be even lower.'"

Dr. Hansen has been one of the loudest and most urgent voices on anthropogenic global warming for the better part of two decades.

Do carbon offsets, in the form of tree planting, really work? They are at best a temporary, stopgap measure to reducing greenhouse gases and at worst, they do little but give the purchaser license to continue to live a high-emission lifestyle because they feel they're at least "doing something" about the problem of climate change.

Trees, as we've discussed here before, are not all created equal. Tropical trees are better than trees in higher latitudes at capturing carbon while trees at higher latitudes are either carbon neutral or, in some cases, actually contribute to global warming, according to researchers. Different species of trees are more effective at carbon capture than others.

Even in tropical areas, tree-planting isn't a long-term solution to global warming. Trees capture carbon as they grow, but once a forest is mature, most of it's carbon-sequestering potential is gone.

Even if I were an advocate for action on AGW (I don't advocate any position), I think I would have a hard time supporting carbon offsets. The potential for corruption is enormous and their benefits are difficult to quantify.

A couple of weeks ago, I wrote about the process of sequestering carbon in soil through a process of heating biomass without oxygen to produce energy and biochar. Research at New South Wales Department of Primary Industries' Wollongbar Agricultural Institute in Australia has shown some of the potential this process holds.

The application of the char - referred to as agrichar in this article - to soil had a dramatic impact in enhancing soil fertility. Production was doubled and in one case - wheat - tripled, and the agrichar will sequester carbon in soil for hundreds of years.

The hybrid Honda Accord, available only in the U.S., hasn't sold well and is being phased out by the auto giant. Honda will continue to make the hybrid version of the Civic, which has had more sales success. Toyota remains the leader in hybrid sales, with the Prius leading the market.

The Accord hybrid focused more on producing power than fuel economy, which I believe is the reason for its lack of success. Taking a look at the numbers for 2007 Accords, the basic 4-door, 4-cylinder model, with 166 horsepower and an automatic transmission (comparing apples to apples, as the hybrid comes only in automatic) gets 24 mpg in the city, 34 mpg on the highway. An Accord with a V6 gas engine producing 244 horsepower with an automatic transmission gets 20 mpg in the city, 29 mpg on the highway. And the V6 hybrid, producing a whopping 253 horsepower gets 28 mpg in the city and 35 mpg on the highway. MSRP without extra options: $20,020.00 for the most basic 4-popper, $25,795.00 for the most basic V6, and $31,685.00 for the hybrid without navigation.

Now, there's a lot of features available on the hybrid that aren't on those more basic cars, but I think that too is part of the problem here. Who is buying hybrids? People who care about the environment and/or people who are willing to pay more for a vehicle upfront which will save money on gas with improved efficiency. I don't think most people looking at hybrids are in the market for a performance sedan with a lot of extras. The Toyota Prius, with an MSRP of $22,795.00 and mileage of 60 mpg in the city and 51 mpg on the highway is far more appealing to the average person shopping for a hybrid, as is the Honda Civic hybrid.

Tomorrow marks the start of the G8 Summit in Heiligendamm, Germany. The Group of Eight consists of Germany, Russia, the United Kingdom, the United States, France, Canada, Italy and Japan. Representatives from other parts of the developing world will also be in attendance, including China, India and Brazil.

President Bush has already made waves among his European counterparts by presenting an initiative which would bring together leaders from the world's 15 biggest greenhouse gas (GHG) emitters to develop long term voluntary emission-reduction goals. Some in Europe see this as a plan to circumvent the existing UN process for addressing climate change. President Bush's play is more of a bottom-up approach for working on reducing greenhouse gas emissions while the UN process is a top-down strategy.

The developing world isn't very happy with any plan to lower GHG emissions, according to the UK Telegraph. China and India have already rejected a mandatory cap on greenhouse gas emissions recommended by the European Union, while Brazilian President Luiz Inacio Lula da Silva has attacked President Bush's plan.

Interesting story last night on the CBS Evening News on the carbon footprint of the G-8 Summit, starting today in Germany. Ferrying world leaders to one location, along with all the press corps and support staff that comes with them, is an expensive and carbon-intensive proposition. Sorry, no way to bypass the commercial at the beginning of the video clip.

Much was made last week of NASA administrator Michael Griffin's comments on NPR on the relative merits of global warming as an issue. Mr. Griffin has now told scientists and engineers at NASA's Jet Propulsion Laboratory that he regrets his remarks.

Why did he apologize? Not for his opinion, which while not perhaps popular is certainly a valid opinion, but for creating controversy.

Griffin reiterated that NASA's job was to provide scientific data on global warming and leave it up to policy makers to decide what to do with it.

A new study by scientists from UC Irvine have determined that dirty snow can explain one-third or more of Arctic warming mostly associated with greenhouse gases. The snow becomes dirty when soot from tailpipes, smokestacks and forest fires gets into the atmosphere and then falls back to the ground. The sooty snow is dirtier and darker than snow without soot, meaning it absorbs more sunlight. Pure white snow is more efficient at reflecting the sun's light and heat energy.

The scientists believe that the sooty snow can explain up to 19 percent of total global warming in the last 200 years, and at least one third (and perhaps as much as 94 percent) of warming in the Arctic.

The majority of the soot comes from industry and fuel consumption, which means that although this is not greenhouse gas warming, it is still anthropogenic warming. The researchers say that limiting industrial soot emissions and using cleaner-burning fuels would brighten snow and have an immediate impact on the Arctic.

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Katie Fehlinger has some global warming headlines I haven't touched on here, and an interview with Dan Lashof of the Natural Resources Defense Council.

A new study in the journal Nature reconstructs the past 270 years of Atlantic hurricane history using sediment samples to reconstruct water temperature and coral samples to reconstruct wind shear. Coral density depends on precipitation at the time of growth, which is largely dependent on the strength of trade winds. When the trade winds are strong, wind shear is strong as well.

The results of the study show that several periods of enhanced hurricane frequency, more than four major storms on average per year, have occurred several times over the 270 year period of their reconstruction, with no link between warm sea and air temperatures and the higher hurricane frequency. Researchers point out this data does not predict future hurricane activity.

The full study can be found in this week's edition of Nature, a subscription-only site. One of the points made in the summary of the full study is that more rapid warming in the atmosphere relative to the ocean from the 1970s to the 1990s may have caused the low hurricane frequency during that time.

It's Friday - a good time for a little odd global warming news. Seems the number of cats and kittens being brought to animal shelters in the United States has spiked by about 30 percent over the past couple of years.

Why? Kathy Warnick, president of a national adoption organization called Pets across America says "Cats are typically warm-weather, spring-time breeders. However, states that typically experience primarily longer and colder winters are now seeing shorter, warmer winters, leading to year-round breeding."

With no "reproductive lull," more kittens are being brought to animal shelters during the winter months.

Last week I wrote about Honda pulling the plug on the U.S. only hybrid Accord, a car which produced plenty of power, but not fantastic fuel economy. A day or two after making that post, I was doing a non-work-related search and came across Honda's clean-diesel Accord, which will be available in the U.S. by 2010. The power of a diesel engine, with a whopping 62.8 mpg highway fuel economy. SWEET!

Honda has sold diesel powered Accords in Europe for several years, but this new engine, announced last fall, meets even the most stringent emissions requirements in the United States, through the use of a NOx catalytic converter that "detoxifies" nitrogen oxide by turning it into nitrogen.

India participated in last week's G8 Summit in Germany as one of a group of developing nations. Discussions on cutting greenhouse gas emissions were met with a blunt rejection by Indian Prime Minister Manmohan Singh, who told reporters, "We said we have not come here to discuss targets or accept internationally enforced targets on us."

India is among the world's leaders in carbon dioxide emissions, but with the world's second-largest population at over one billion people, per capita CO₂ production is low, only 23 percent of the global average and just 4 percent of the U.S. average.

College students have been challenged to come up with digital games based on the theme of global warming. The winners will get cash, but even more than that - an invitation to visit Microsoft and present their entry to the Microsoft games management team for possible inclusion in Xbox LIVE Arcade. The first place prize is the opportunity to become an apprentice at Microsoft's Interactive Entertainment Business as part of its internship program.

I have to say when I first read the blog entry that I linked above, the thought crossed my mind that this might be a joke. But no! It's real. Microsoft is teaming up with Games for Change (G4C) to bring together the worlds of gaming and of social change. Gamers aren't the first group that comes to my mind when I think of the environmentally conscious, but G4C president and co-founder Suzanne Seggerman says, "We know from experience that young people are looking for ways to help make the world a better place, and who better to support this effort than an industry leader like Microsoft?"