People are proposing all kinds of extreme measures to lower gasoline costs, including offshore drilling in areas that would destroy ecosystems despite no additional gas (or savings) for at least a decade.

But there are simple things you can do to immediately lower your gasoline costs by an average of 15 percent. The steps are outlined in a useful new Web site on EcoDriving sponsored by the Alliance of Automobile Manufacturers. The site is user-friendly, and offers a variety of educational tools, including an informative video and extensive tips on fuel-efficient driving and maintenance practices.

Memorial Day is the start of the summer travel season. With gas prices approaching $4 per gallon across the country, you might want to think carefully about how you get where you're going. Should you take one, big, packed car, or two smaller, half-empty cars? How much gas can you save by driving slower and making sure your car engine is properly tuned?

For answers to all these questions and more, check out our Eight Ways to Green Your Road Trip.

When you save water, you save energy – and vice versa. Carbon calculators can give you some idea of your carbon footprint, but most don't take into account your water usage. How much water do you use? Now you can find out.

A new Web site, H₂O Conserve, offers an H₂O Calculator. I tried it, and it said I used 479.88 gallons per day (I do?). The average American uses 1189.3 gallons of water per day, so I guess it's not as bad as it sounds.

The site also includes a comprehensive tips section for learning how to use less water.

Have you ever been on weight-loss diet, gone to a function with delicious-looking desserts, and told yourself, "One cookie isn't going to make me fat"? One cookie may not make you fat, but how many "cookie moments" occur during your day, your week? If your answer is always that this one little cookie can't hurt, you will not lose weight.

Conserving energy is sort of like going on a group diet where every person, dozens of times a day, has a "cookie moment". Does it really matter if I leave on the lights in my home when I go out? Does it really matter if I don't recycle this container? Does it really matter if I keep my chargers plugged in when not in use?

The short answer is yes, it matters. There are a myriad of things you can do to conserve energy and fight global warming. Each action by itself is small and painless, but taken together the effect can be huge. Here's a list of easy things you can do that will make a big difference.

Most of the electricity in this country comes from coal-fired plants that emit huge amounts of carbon, so:

• Turn off the light when you leave a room, and turn off all the lights when you leave your home.
• Change your bulbs to compact fluorescents (now – don't wait for the old bulbs to burn out).
• Don't leave chargers plugged in when not in use. They suck up electricity just sitting there.
• Buy energy-efficient appliances.
• Turn off your computer at night rather than leaving it in stand-by mode.
• Many appliances, such as televisions, can't be completely turned off except by unplugging them. Appliances in stand-by mode account for 5 percent of the electricity used in the U.S. To turn them off completely, use a power strip.

Paper comes from trees, which suck up carbon, so:

• Buy recycled paper products. Visit our Paper Calculator to learn more about why this helps.
• Use only the paper towels and toilet paper that you need.
• Only print out emails and articles when you really need to.
• Recycle paper – newspapers, magazines, scratch paper, junk mail, everything you can. You can cancel unwanted catalogs at Catalog Choice.

• Bring a reusable shopping bag with you to the store.

Manufacturing products of any kind uses energy and creates emissions, so:

• Don't buy things you don't need and won't use.
• Borrow from your local library instead of buying books you'll read only once.
• Give away or recycle what you no longer want. Give old eyeglasses to your local eyeglass store – they can pass them onto people in need. Bring your old cell phone back to the cell phone store for recycling. Give away old appliances, computers, clothes, etc. Earth 911 can help you find recycling resources.

It takes a significant amount of electricity to supply municipal water, so:

• Take showers instead of baths, and don't linger in the shower.
• Turn off the water while brushing your teeth.
• Don't run dish washers and clothes washers half full.
• Don't water your lawn unnecessarily.
• Fix leaky faucets, and install low-flow faucets and shower heads.
• Check out more water conservation tips from the EPA.

Heating and cooling use a lot of electricity, so:

• Make sure your house is adequately insulated. If snow melts quickly off your roof, you need more insulation in the attic.
• Wrap your water heater in insulation.
• Wash clothes in cold water – they will still be clean, and they'll last longer, too.
• Line-dry clothes if you can, instead of using a clothes dryer.
• Keep your thermostat down in winter and up in summer – don't overheat or overcool your home.

Cars are a major source of greenhouse gas emissions, so:

• Group your errands so you only drive into town once for all the things you need to buy and do.
• Have your car tuned regularly, and check tire pressure. An
  untuned engine burns more gas, as do cars with underpressurized tires.
• When buying a new car, buy the vehicle with the best mileage that meets your needs.
• Walk, bike, or use public transportation instead of driving whenever possible. If you have to drive, carpool where possible.
• See our previous post for more tips for cleaner driving.

If you're willing to go to greater lengths, that's wonderful. See "No Impact Man" for how a New Yorker completely eliminated his carbon footprint. Many homeowners are finding that lowered costs and state subsidies are making solar panels much more affordable. But you don't have to do the hard stuff to make a difference. Every little bit counts.

You can find more tips and ideas on our Fight Global Warming Web site.

In 1800, 3 percent of the world's people lived in urban areas. In the last year, that number is likely to have passed 50 percent [PDF]. The world is becoming urbanized at an extremely fast rate, and as the urban population increases, so does urban development.

This presents an opportunity in the fight against global warming, since energy use in buildings accounts for 40 percent of greenhouse gas emissions in the U.S.

You might think it costs a lot more to make a building energy efficient, but it doesn't have to. A building that produces half the usual emissions can cost as little as 1 percent more to build. How can that be?

Green buildings can be cost effective because payback is not only in future energy use. For example, if you spend more on high insulation windows, you may be able to save money with a smaller furnace.

Green buildings are going up all over the world:

• Federal Building, San Francisco – 50 percent less energy use than standard office towers.
• Bank of America Tower, NYC – planned LEED Platinum certification.
• Pearl River Tower, Guangzhou, China – net energy footprint of zero.
• Le Phare (The Lighthouse), Paris, France – powered by wind turbines.

But it's not all about new construction. Retrofitting existing buildings is just as important as making new buildings energy efficient. New York City's PlaNYC, a plan for managing the city's growth through 2030, says that while new construction is one focus area, "We have focused primarily on upgrades to existing buildings, since they will still form the overwhelming majority of our building stock by 2030." "[R]eplacing outdated lighting systems with more energy-efficient models" and "improved[d] standards for appliances and electronics … can achieve enormous savings" in usage and energy bills.

The renovation of the U.N. building, scheduled for completion in 2014, is a case in point. The revamped building will look the same as it always has, but its energy bill, which was $30 million in 2004, will be at least 40 percent lower.

How do you make a building green? Well, it depends on where it is. If it's a place that gets a lot of sun, solar energy might work. If it's a windy locale, wind turbines might be the better choice. Glass, no glass, windows facing the sun or not – these are all decisions that depend on the environment in which you're building. Standard buildings impose their artificially created climate on their environment. Green buildings work with the environment, rather than fighting against it.

You can learn more about sustainable urban development in Environmental Defense's Green Renaissance [PDF] report, which gives detailed descriptions of green buildings in New York City.

Consumers and businesses alike complain that it takes years for savings on energy bills to repay the up-front costs of energy efficiency. No longer. As the Wall Street Journal recently reported, lenders have discovered what energy analysts have known for years: loans for energy efficiency improvements are low-risk, because borrowers can "finance" these loans through lower energy payments.

Energy-efficient mortgages have been available for some time, but lenders didn't promote them, and customers resisted the extra inspections and paperwork. Now to get home buyers interested, banks are offering incentives of $500-$1000 off closing costs. Everybody wins: consumers save money, lenders make a profit, and the atmosphere enjoys lower carbon emissions.

It works like this. Potential borrowers schedule an energy audit by an approved third-party company. The auditor identifies improvements that will lower energy costs, and calculates how much will be saved. Say a set of home improvements will save $50 a month. For a 30-year mortgage, this adds about $10,000 of qualifying income, depending on the interest rate. If the mortgage is approved, the lender puts the money for the improvements into an escrow account. The borrower makes the improvements after the home is purchased, and pays the costs over the life of the mortgage.

Energy-efficient mortgages are available for newly constructed homes as well, and offer an incentive for builders to add in efficiencies that they might not otherwise. Home builders have been reluctant to make energy-efficiency a priority for fear buyers would find the homes too expensive. Energy-efficiency loans largely eliminate this problem. Homes that are already energy efficient can be audited, and the projected energy savings counted as extra income for the borrower.

It's not just mortgage lenders who are getting into the act. Some states – for example, Pennsylvania, Kansas, and New York – are subsidizing unsecured, low-interest loans for energy-efficient improvements.

These loans are a great idea, and I hope they become a routine part of buying a home. A U.S. Department of Energy study estimates that efficiency improvements in U.S. homes could lower energy usage 20 percent by 2020. A U.N. Foundation study [PDF] arrived at a similar conclusion – efficiency improvements could lower energy usage 30 percent or more by 2030. That's nearly 500 million metric tons of CO₂. When one considers that 20 percent of U.S. carbon dioxide emissions are attributable to home heating and electricity use, it's clear that the potential savings are enormous.

They say knowledge is power. That's the idea behind an interesting innovation in the U.K. called "smart meters" which tell people in real time how much energy their appliances are using, and how much carbon is being emitted as a result. The goal is to change usage patterns by giving immediate feedback.

Energy usage feedback devices are starting to appear in the U.S., as well.

The "Kill A Watt" meter can tell you how much energy each of your appliances is drawing. You plug the appliance into the Kill A Watt, then plug the Kill A Watt into the wall.

Another device, called the Orb, changes color depending on the current price of electricity, thus encouraging people to use energy at off-peak times when it's cheaper.

It's hard to manage something that you can't see. Smart meters, by making the invisible visible, allow people to make smart choices about the appliances they use, how they use them, and when they use them. The lower your energy usage, the lower your carbon footprint.