Here is our final question-and-answer session with Dr. Richard Alley, Evan Pugh Professor of Geosciences at Penn State. To review, Dr. Alley studies paleoclimates from ice cores and is one of the authors of the IPCC's 4th Assessment.

I'd like to say thank to you to Dr. Alley for sharing so much information with the blog over the last couple of weeks.

Question: Dr. Alley, how can you tell what forcings were involved with past climate changes?

Dr. Alley's Answer: One can use strength of magnetization of lava flows and sediments to learn about the strength of the magnetic field, and then the changes in cosmic-ray-produced things not explained by the magnetic field are probably changes in the sun (we don't think the total cosmic ray flux changes much). There are small changes in the sun recorded, and small changes in climate going along, with a behavior that matches what we expect. The large changes in magnetic field that have happened don't seem to have had an effect on climate, so that doesn't seem to be an important forcing. There is little evidence of changes in micrometeorites/space dust (except for the occasional giant meteorite such as the one way back that killed the dinosaurs), so space dust doesn't seem important. Volcanoes block the sun and bring cold--a degree or two for a year or two--this is well-recorded, but isn't "organized"--one eruption doesn't trigger another, so the volcanoes mostly make "noise". The very skinny version is that climate has been mostly controlled by sun (with small changes in total brightness giving small climate changes), and by greenhouse gases (mostly CO2). In addition, features of Earth's orbit (which move the sunshine around over the planet over tens of thousands of years--more in the north or the south, or more at the equator or the poles) have paced ice ages, in part by affecting CO2. Over long times, drifting continents affect where ocean currents go and other such things, which matter to climate.

Question: What degree of confidence do paleoclimatologists have in the climate reconstructions? Does it diminish farther back in time?

Dr. Alley's Answer: Given the huge range of indicators, the degree of confidence goes from pound-on-the-table/this-is-almost-surely-right to this-is-more-likely-than-not-to-be-right/can't-say-much-more. In general, confidence is better more recently.

Question: Can you compare the current warming in the Arctic with the warming of the 1930s and 1940s? What were the climate forcings that brought on that warming?

Dr. Alley's answer: This is still a topic of research, but the recent paper by Johannessen et al., and other work, give good pointers. The most obvious difference between the earlier warming in the Arctic, and the more recent one, is that the earlier one was mostly restricted to the Arctic, and the more-recent one is almost everywhere. The geographic pattern of the earlier one did not look like that expected for greenhouse gases (which had not risen much yet), and the more recent one does look like the greenhouse-gas pattern. Some worker points to a role for sun and volcanoes in the earlier one (occasionally, by accident, brighter sun and fewer volcanoes happen at the same time), together with a "dynamic" component--perhaps a change in the ocean overturning linked to the Atlantic Meridional Oscillation. The climate is a complex-enough beast that glib answers should be viewed with caution--the IPCC or National Academy statements on global warming are NOT glib, but are cautious and carefully reasoned, and must be.

Recently, AccuWeather.com Expert Senior Meteorologist Elliot Abrams raised questions about this winter's weather and asked his readers whether they believed global warming played a role in the extremes. Many of the answers he received were well thought out, and I thought it would make sense to provide a link to them here.

I found another article yesterday on the Inuit delegation appearing before the Inter-American Commission on Human Rights. The article adds some additional information to what we learned from the article I linked back on February 23. The group appeared before the human rights committee Thursday. The most significant fact the new article includes is that the commission, part of the Organization of American States, has no authority over the United States government. Basically, the Inuit are trying to draw more attention to the issue of climate change, and to help make it a bigger issue in American politics.

USA Today had an interesting article on Tuesday titled Global Warming a Hot Spot for Investors. The article singled out climate change as the major investment theme of the future. Financial services firms are busily working, trying to figure out which stocks and sectors will be helped and which will be hurt by climate change.

For investors, it doesn't matter if global warming is real or if man is causing it - what matters is how people react to the perceived threat. Money will be made, and lost, based on who winds up being the winners and losers in the battle against climate change. Will ethanol be the fuel of the future for cars? Will it be produced from corn, or from some other source of biomass? What about biodiesel? Or hydrogen? What if someone comes up with a device that scrubs carbon dioxide from the atmosphere and claims that $25 million prize from Richard Branson? That could turn a small start-up company into the next MicroSoft. Only time will tell where the money will go. But there is money to be made from climate change. Lots of it.

Answer: Start a small-scale nuclear war.

(please note - it's Friday afternoon, and it's just a joke.)

In an address Thursday, U.N. Secretary-General Ban Ki-moon said global warming presents as great a threat to the world as war. He then urged the United States to lead the fight against global warming. Ban will emphasize the climate crisis in a June meeting in Germany with the Group of Eight industrialized nations - Canada, France, Germany, Italy, Japan, Britain, the United States and Russia.

"The majority of the United Nations work still focuses on preventing and ending conflict," Ban told an international U.N. school conference on global warming. "But the danger posed by war to all of humanity and to our planet is at least matched by the climate crisis and global warming."

"In coming decades, changes in our environment and the resulting upheavals from droughts to inundated coastal areas to loss of arable land are likely to become a major driver of war and conflict," said Ban, who became U.N. chief on Jan. 1.

Just a quick note - The CBS Evening News will be beginning a series of reports on global warming on tonight's broadcast.

I don't know what to say about this.

In the ski resort business, the weather is everything. Even if the snow doesn't fall, cold weather allows snowmaking. When the cold doesn't come, the ski season gets shortened and the profits go downhill faster than those insane skiers in the Olympics. The key in Aspen?

"To be in business," says Patrick O'Donnell, who was Aspen's CEO and environmental conscience for a decade before retiring in November, "we rely on putting down 2 feet of good [artificial] snow, good hard snow that we make the last two weeks of October and the first two weeks of November. That way, when March comes, we can still have skiing, we can still get a full rate for our lift tickets."

Aspen's been on the edge in recent years, making snow within a degree or a degree and a half of being able to. Understandably, they have more than a passing interest in global warming, and a greater sense of urgency than most of us about making the kinds of changes that could slow warming down. Aspen has made some significant changes in their business practices to reduce their emissions, and hope to have an impact on the way others live as well. Much as NASCAR could bring alternative fuels into the forefront for its legion of fans, Aspen hopes to inspire the 55 million skiers in this country (many of them affluent) to drive change by taking political action, supporting advocacy groups and making changes in their own lives to reduce their carbon footprints.

Aspen can drive change, but it may well be too late to save that one degree - even if greenhouse gas emissions dropped tremendously today, climate scientists say warming will continue for decades.

The Union of Concerned Scientists put their engineers to work to develop an inexpensive minivan which would meet or exceed the most strict greenhouse gas emissions standards in the nation (those adopted by California and 10 other states and currently being challenged in court by automakers). The design uses a combination of existing technologies which would add only about $300 to the sticker price of a minivan and would result in savings of $1300 over the lifetime of the vehicle.

The minivan, named the Vanguard by the UCS, is not a hybrid. It's a flex-fuel vehicle which also features variable valve timing, a 6-speed "automatic-manual" transmission and cylinder deactivation, which shuts down half the cylinders in a large engine when full power is not needed, as well as a host of other features to improve emissions. All of these features are available in some vehicles currently, but no vehicle uses them all.

The full technical report is available as a pdf file, and includes specific cost savings and emissions savings statistics.

Problems with the Vanguard? Well, the availability of E85, mostly. Here in Pennsylvania, only 11 stations available to the public sell E85. California currently has only one station open to the public. Production of ethanol from corn will always be limited by the supply of the crop. Competition of use between ethanol production and animal feed will drive prices higher. Research continues on other crop possibilities which could make E85 a more viable alternative for a large number of vehicles.

That CBS series is going to start tonight - either I miss-heard the announcement yesterday morning or they changed it due to time constraints. Anyway, the series is called Global Warming, Cool Solutions, so those of you hoping for some coverage for skeptics can stop holding your breath right now.

For those of you who have the Discovery Science channel, I'd recommend the episode of Futurecar which will air Wednesday evening at 10 PM Eastern time. This week's episode is all about fuel. They cover ethanol, biodiesel, hybrids, electric, hydrogen, solar and air (yep, compressed air power). It's pretty interesting, though with so many alternatives covered, it's not very in depth.

On an off-topic note - I would appreciate it if the comments would stay a little more on-point; this is a global warming blog, not a political blog.

I got sent a link to some quirky little PSAs produced by Penn State Public Broadcasting with funding from the West Penn Power Sustainable Energy Fund (WPPSEF).

The point of the spots is to encourage people to save energy by taking small, easy steps, and used the angle of saving money to be more effective.

Whenever I read about biofuels, I end up with a lot of questions about land use and hidden costs involved in the growing, harvesting and processing of the crops involved. One statistic I read some time ago stated that if all U.S. corn and soybean production was dedicated to producing biofuels, it would only meet 12% of gasoline demand and 6% of diesel demand, and of course would massively impact food supplies.

The grasses can be grown on land which has been depleted by agriculture. Irrigation is required only as the grasses become established. No cultivation is required, and herbicide treatment is not required. Only phosphorus replacement fertilization would be needed, as legumes provide needed nitrogen. All aboveground biomass is used to produce energy, rather than just the seed. The gross bioenergy yield from LIHD plots was 68.1 Gj ha^-1year^-1. Fossil energy needed for biomass production, harvest and transport to a biofuel production facility was estimated at 4.0 Gj ha^-1year^-1. The article goes on to break down a number of different potential energy production numbers depending on how the biomass is used.

Conversion into gasoline and diesel synfuels and electricity via integrated gasification and combined cycle technology with Fischer-Tropsch hydrocarbon synthesis (IGCC-FT) is estimated to net 28.4 GJ ha^-1. In contrast, net energy gains from corn and soybeans from fertile agricultural soils are 18.8 GJ ha^-1 for corn grain ethanol and 14.4 GJ ha^-1 for soybean biodiesel. Thus, LIHD biomass converted via IGCC-FT yields 51% more usable energy per hectare from degraded infertile land than does corn grain ethanol from fertile soils.

Another benefit of using perennial grasses for biofuel production is a net annual carbon storage in the soil. LIHD plots sequestered 4.4 megagrams of carbon dioxide per hectare per year in soil and roots for the decade of observation. The trend seems to indicate that number would diminish somewhat in a second decade, but would still be much higher than what other crops store.

Without accounting for CO₂ storage, 5x10⁸ ha of agriculturally abandoned and depleted land might produce about 13% of global transportation fuel and 19% of global electricity consumption. A hectare is 10,000 square meters.

I said yesterday I wanted the comments to be more on-topic and less political. And apparently no one understood that those two points were related. In other words - you want to make a comment involving Al Gore, Barbara Boxer, James Inhofe or any other political figure who has made public comments or offered legislation about global warming, that is 100 percent fair game. You want to make a comment on the Iraq war? This is not the place. This is a global warming blog, not a political blog. Want to comment on 2008 presidential candidates? Their opinions and potential actions on global warming are fair game. Their opinions and potential actions on stem cell research, the war on terror or any other issue are not.

Many posters have done a good job curtailing the insults which were getting out of hand a month or so ago. Still, I've been disappointed with the condescending tone of many of the comments recently, and I will not post any comments I think are over the line. This applies equally to people of every political persuasion.