One of the things climate scientists worry about is feedback mechanisms. Some feedbacks are positive- they amplify warming, and some are negative - they suppress warming. Let's take a quick look at a graphic showing how cold air is made. Basically, what this graphic is showing us is that at this time of the year, when the Arctic is receiving little sunlight, the radiative input is less than the radiative output. In other words, more energy leaves the Earth than is added by the sun and cooling occurs.

In addition to that part of the equation, the radiative output (energy lost) is increased by the snow and ice on the ground. Anyone who has experienced snow knows how well it reflects light. It is possible to become "snowblind" from exposure to the bright sunlight and UV rays reflected by the snow. You see, it's not just the light that is reflected by snow, it is also the other portions of the sun's energy, including it's heat that is reflected away from the Earth's surface.

So what does this have to do with global warming? You have probably heard about concerns over the diminishing ice in Greenland and elsewhere in the Arctic as well as in Antarctica. In areas where the ice melts, revealing land or ocean beneath it, less of the sun's heat is reflected back to space and more is absorbed. Since it is the sun's energy absorbed by the Earth that warms the atmosphere, the melting ice can become a positive feedback and cause the Earth to warm faster.

We all know carbon dioxide, a naturally occurring chemical - the product of the respiration of every animal on earth - which is also produced by the burning of fossil fuels such as oil, coal and natural gas. And some of us may have also heard about methane, another of the greenhouse gases, which may also have a significant role in global warming over the next few decades (I'll post more on methane another day - it gives me a headache). But today from Japan comes a report on yet another greenhouse gas. Dinitrogen oxide, which originates from nitrogen-based fertilizers used on farms. The chemical was measured through the use of ice cores taken from Antarctica and has been increasing slowly for the past 50+ years.

Little darlin' - oh, sorry. Beatles tangent. What if the sun and it's energy variations have more to do with climate change than any greenhouse gasses? Seem unlikely? Maybe, but there are certainly a number of scientists who are looking into these links. Elliot Abrams noted some in his blog in September. Here's a link to a lecture by Sallie Baliunas, Ph.D. from back in 2002. In the interest of being forthright, I will state here that some are critical of Dr. Baliunas' connections to the Marshall Institute, which receives a fraction of it's funding from oil companies (or at least from Exxon-Mobil).

And here's a link I got from Jesse Ferrell's blog back in September to an article about upcoming global COOLING, based on solar emission research.

By the way, Jesse's blog has some of the best weather pictures around. Check it out! And thanks to all our site visitors who have contributed pictures to our AccuWeather.com photo gallery. There's a lot of beautiful shots there, including this one which seems appropriate today.

When in read a summary of this article from the Denver Post, and it mentioned hurricane expert Dr. Bill Gray, I expected an explanation of Dr. Gray's well-known skepticism over global warming. What I got was a whole lot more. A very sound overview of the difficulties of modeling the climate, and an unbiased representation of both sides of the global warming issue. Read this one, folks. It's worth the time.

I've had some questions about the greenhouse effect and greenhouse gases, so I figured now would be as good a time as any to provide a little overview of the subject.

First of all, it's important to note that the greenhouse effect and global warming are NOT the same thing. Greenhouse gases and the greenhouse effect have always been with us, and in fact makes the Earth habitable. If the Earth had no atmosphere, it would average about 30 degrees Celsius (about 50 degrees Farenheit) lower than it does at present.

(Image From Global Warming Art)

So how does the atmosphere help keep the Earth warm? Most of the sun's radiation has a short wavelength. It's mostly in and near the visible parts of the spectrum. The atmosphere is mostly transparent to visible light, which is absorbed by the Earth's surface. As the surface warms, it radiates longer wavelength radiation which warms the atmosphere. Those areas which receive more sunlight warm the most, and land warms much faster than water. And of course, some surfaces on the land absorb more of the sun's radiation and heat up faster, as anyone who has walked from a grassy park onto an asphalt parking lot on a hot July afternoon knows. The radiation absorbed by the atmosphere is then emitted in all directions, some going back to Earth, some going out to space. This whole process is complicated further by the presence of clouds, which can reflect some of the incoming solar radiation and can also prevent the day's heating from escaping back to space at night.

Greenhouse gases include water vapor (the most abundant by far), carbon dioxide and methane. The concern among many climate scientists is that increasing amounts of CO2 will increase the overall global temperature (global warming) and have a damaging effect on the Earth's climate.

Here's a good resource on bad greenhouse meteorology.

As I mentioned before, I've spent almost 20 years forecasting the weather. That means I've spent WAY too much time looking at computer models. I'm enough of an old-timer to remember the baroclinic and the LFM, though of course I have had much more experience with the NGM, the ETA (NAM, WRF, whatever they're calling it this week) and the longer range models like the European and the GFS.

Those years of experience have taught me two things. First, computer models have glaring weaknesses. Some would say they stink. Some would say worse. There is just so much complexity in the atmosphere which has to be simplified for the sake of number-crunching time that they can't capture everything that happens. And sometimes that results in massive error. Second, meteorologists can't function without them. While I still think you get more accuracy in the first 6-12 hours of a forecast by looking at the NOW - satellites, radar, surface and upper level charts - the models are better than "classical methods" farther out. So it's sort of a love-hate relationship.

Climate models are really a different animal from weather forecasting models, but it's difficult for my forecaster brain to get away from my feeling that models are not entirely to be trusted. Nonetheless, models are one of the primary methods climate scientists use to predict climate change. Here's an excellent overview of what climate models are and how they work from Gavin Schmidt, a climate modeller at the NASA Goddard Institute for Space Studies.

Now if you really want to have fun.....and you have a half-way decent PC (or Mac) that can be pretty much dedicated to a project for a couple of days, you too can become a climate modeller! Columbia University has an educational Global Climate Model which uses NASA GISS' GCM II but can be run on a desktop. This software was developed for use with students from 9th grade through grad school. Any teachers reading this may be interested in using this tool in their classrooms.

Just a couple of notes on this model, I downloaded it a couple of weeks ago on a Friday and ran it on my rather elderly, 400 MHz processor Mac. It ran like a top - no problems with it even though I had to work a rare forecasting shift on Saturday and I had multiple applications running with the GCM in the background. However, it took from Friday evening to midday Monday to run a 50 year simulation. I would love to see what I could do running this on a newer system with something near 2 GHz processing speed. There are a bunch of simulations which can be run if you've got the speed to do it.

The American Meteorological Society has drafted a statement on Climate Change. The statement can be found by following the link halfway down the page. Members of the AMS are welcome to submit their comments to the AMS Council. The statement is a fairly complete overview of the AMS' opinion.

Ahhhhh.....methane. What could be a better topic for today? I wish I knew, because methane is one of the most difficult topics around when it comes to greenhouse gases. Well, first the good news. A new study, summarized here, finds that atmospheric methane has stabilized, possibly due to leak repairs at oil and gas pipelines and storage facilities and perhaps from reduced or slower growth of emissions from coal mining, natural gas production and rice paddies. Methane is also released into the atmosphere by a number of natural phenomena, such as biomass burning, volcanic eruptions and the melting of methane hydrates in permafrost. Oh, and it also results from cows - as Henry noted in a November 6th entry on his MeteoMadness blog.

The fact that methane is currently stable in the atmosphere is a good thing, but this entry at RealClimate.org makes it fairly clear that our understanding of methane variations is limited, to say the least. We simply can not use the data we have now to construct any sort of accurate forecast for future methane concentrations. Given that methane is a more potent (though shorter-lived) greenhouse gas than carbon dioxide, and given that methane in the atmosphere oxides into carbon dioxide, this is another area where more research is needed.

I'm not sure how many of the readers of this blog follow up and read comments, so I thought I would add this link to an entry on the main page. Thanks to Sarah Fortner for adding it to our discussion. This is an op-ed piece from Peter Doran, an associate professor of earth and environmental sciences at the University of Illinois at Chicago. It was his research which discovered the regional cooling in portions of Antarctica. The op-ed addresses how this research has been mis-used by the media and others as "evidence" against global warming. It makes a very interesting read.

I don't know how many of you have followed up with the story I linked a couple of days ago, so here is a reminder about the MSNBC reporter and photojournalist visiting Antarctica. They are there to observe a massive drilling project going on there. I'm linking the second page of the article, because that's the story of his journey to Antarctica. The first page then tells the story of the reporters first trip onto the Ross Ice Shelf. If you follow the link to the interactive page, you can listen to a lot of information about Antarctica and what makes it so interesting to researchers.

Here is a map to get you acclimated with the scene. The men are staying at McMurdo Station, which is located near the coast along the bottom of this image (tempting to say southern coast, but that would not be accurate!). McMurdo is located right at the rim of the Texas-size Ross Ice Shelf. That ice shelf sits over the water and helps to hold back the ice which is over land on Antarctica. If it were to break away from the continent, some of the ice on land would slip into the sea as well.

RealClimate has a post from last week which offers some new information on the "Little Ice Age" - the period of cooling, at least in the Northern Hemisphere, which occurred between the late 16th and some say the late 17th century. Others argue the LIA ended in the mid-19th century.

A study published in Nature by Lund et al (subscription required) explains how examination of the remains of tiny animals called foraminifera in sediments off the coast of Florida reveal the Gulf Stream, at least through the Florida Straights, may have weakened by a