Global warming is a very real threat.
• Average temperatures have climbed 1.4 degrees Fahrenheit (0.8 degree Celsius) around the world since 1880, much of this in recent decades, according to NASA's Goddard Institute for Space Studies.
• The rate of warming is increasing. The 20th century's last two decades were the hottest in 400 years and possibly the warmest for several millennia, according to a number of climate studies. And the United Nations' Intergovernmental Panel on Climate Change (IPCC) reports that 11 of the past 12 years are among the dozen warmest since 1850.
• The Arctic is feeling the effects the most. Average temperatures in Alaska, western Canada, and eastern Russia have risen at twice the global average, according to the multinational Arctic Climate Impact Assessment report compiled between 2000 and 2004.
• Arctic ice is rapidly disappearing, and the region may have its first completely ice-free summer by 2040 or earlier. Polar bears and indigenous cultures are already suffering from the sea-ice loss.
• Glaciers and mountain snows are rapidly melting—for example, Montana's Glacier National Park now has only 27 glaciers, versus 150 in 1910. In the Northern Hemisphere, thaws also come a week earlier in spring and freezes begin a week later.
• Coral reefs, which are highly sensitive to small changes in water temperature, suffered the worst bleaching—or die-off in response to stress—ever recorded in 1998, with some areas seeing bleach rates of 70 percent. Experts expect these sorts of events to increase in frequency and intensity in the next 50 years as sea temperatures rise.
• An upsurge in the amount of extreme weather events, such as wildfires, heat waves, and strong tropical storms, is also attributed in part to climate change by some experts.
So are we humans causing it? "Very likely," the IPCC said in a February 2007 report. The report, based on the work of some 2,500 scientists in more than 130 countries, concluded that humans have caused all or most of the current planetary warming. Human-caused global warming is often called anthropogenic climate change.
• Industrialization, deforestation, and pollution have greatly increased atmospheric concentrations of water vapor, carbon dioxide, methane, and nitrous oxide, all greenhouse gases that help trap heat near Earth's surface.
• Humans are pouring carbon dioxide into the atmosphere much faster than plants and oceans can absorb it.
• These gases persist in the atmosphere for years, meaning that even if such emissions were eliminated today, it would not immediately stop global warming.
• Some experts point out that natural cycles in Earth's orbit can alter the planet's exposure to sunlight, which may explain the current trend. Earth has indeed experienced warming and cooling cycles roughly every hundred thousand years due to these orbital shifts, but such changes have occurred over the span of several centuries. Today's changes have taken place over the past hundred years or less.
• Other recent research has suggested that the effects of variations in the sun's output are "negligible" as a factor in warming, but other, more complicated solar mechanisms could possibly play a role.
What might happen? 
A follow-up report by the IPCC released in April 2007 warned that global warming could lead to large-scale food and water shortages and have catastrophic effects on wildlife.
• Sea level could rise between 7 and 23 inches (18 to 59 centimeters) by century's end, the IPCC's February 2007 report projects. Rises of just 4 inches (10 centimeters) could flood many South Seas islands and swamp large parts of Southeast Asia.
• Some hundred million people live within 3 feet (1 meter) of mean sea level, and much of the world's population is concentrated in vulnerable coastal cities. In the U.S., Louisiana and Florida are especially at risk.
• Glaciers around the world could melt, causing sea levels to rise while creating water shortages in regions dependent on runoff for fresh water.
• Strong hurricanes, droughts, heat waves, wildfires, and other natural disasters may become commonplace in many parts of the world. The growth of deserts may also cause food shortages in many places.
• More than a million species face extinction from disappearing habitat, changing ecosystems, and acidifying oceans.
• The ocean's circulation system, known as the ocean conveyor belt, could be permanently altered, causing a mini-ice age in Western Europe and other rapid changes.
• At some point in the future, warming could become uncontrollable by creating a so-called positive feedback effect. Rising temperatures could release additional greenhouse gases by unlocking methane in permafrost and undersea deposits, freeing carbon trapped in sea ice, and causing increased evaporation of water.
What can we do about it right now?. 
1.
Change your light bulbs. If every household in the U.S. replaced a burned-out bulb with an energy-efficient, ENERGY STAR qualified compact fluorescent bulb, the cumulative effect is enormous. It would prevent greenhouse gas emissions equivalent to that from nearly 800,000 cars. It would also save enough energy to light 2.5 million homes for a year.
2.
Drive less. On average, a passenger car emits 11,400 pounds of CO2 each year while a home emits 9,000 pounds of CO2 per person each year in the United States. And since we all can't afford to by a Hybrid right now, leaving your car at home two days a week will reduce your CO2 emissions by 1,590 pounds a year.
3.
Strip down, bundle up! Add two degrees to the AC thermostat in summer, and two degrees in winter. Better yet, ceiling fans use 80% less energy than central air conditioners. By only using ceiling fans you can reduce your annual cooling costs by 10-65%. In warm weather run the fan blades in a counter-clockwise direction to feel 5 degrees cooler. During the winter set the fan blades to rotate clockwise at a low speed to force warm air from the ceiling down into the living space. Also, if 1 in 10 households serviced heating and cooling systems annually, cleaned or replaced filters regularly, used a programmable thermostat and replaced old equipment with ENERGY STAR models it would prevent the emissions of more than 17 billion pounds of greenhouse gases.
4.
Watch out for the refrigerator! Your refrigerator is the biggest consumer of electricity among household appliances and responsible for 10-15% of the electricity you use each year. Don't set the thermostat too high. Lowering the temperature even 1 degree will make a big difference. If your refrigerator is near a heating vent, or always in the sun, then change the location, cover up the heating vent near it or cover the window. Turn on your "energy saver" switch near the thermostat. Clean the condenser coil. This one, very simple thing can improve the efficiency of your refrigerator reducing your annual energy costs by $20. Make sure the doors seal properly, and keep the cool in.
5.
But don't turn your back on the the hot water heater, the washer and dryer, or the dishwasher. Either turn the hot water heater down to 120 degrees, or turn on the "energy conservation" setting. For each 10 degrees reduction in water temperature, you can save 3-5% in energy costs. Buy insulation at a local store and insulate your hot water heater and pipes. Install a timer on your water heater to turn off at night and on just before you wake up in the morning. Don't pre-rinse dishes. Today's detergents are powerful enough to do the job. Wait until you have a full load to run the dishwasher. Wash clothes in cold water, not hot. Ninety percent of the energy used in operating a washing machine goes toward heating the water that washes and rinses the clothes. Don't over-dry your clothes. Better yet, hang dry!
6.
Garden wisely. While it is true that planting more trees will help in the short term because they essentially soak up carbon, they also release carbon dioxide when they die. So it just postpones the problem. But there are other reasons to plant trees - as wind breaks to save energy and as shade to lower cooling costs. As for plants, choose hardier plants that need less water. Plant flowers that need more water in groups and add mulch to help keep moisture in. Water your lawn sparingly.
7.
Buy Green Energy and invest in green energy stocks. Imagine if we ran out of fossil fuels tomorrow, what would we do? Well, we'd get our electricity from renewable energy, such as solar panels, geothermal and wind power sources. Many utilities now give consumers the option to buy "green power." Ask for it! Learn the truth about nuclear power and natural gas as viable "green" options. They aren't. Radioactive waste will be a problem for tens of thousands of years into the future. Even though natural gas emits half as much CO2 as coal, it is still responsible for 20% of CO2 emissions in the United States while only providing us with around 23% of the energy consumed. Natural gas can help us make a transition, but it isn't the solution. Finally, invest in green stocks and renewable energy companies through socially responsible funds.
8.
Go organic. Even with our vast reservoir of scientific knowledge about farming, most American farmers still spray a billion pounds of pesticides to protect crops each year. Now here's the kicker: when chemical pesticides are used to kill pests, they can also kill microorganisms that keep carbon contained in the soil. When the microorganisms are gone, the carbon is released into the atmosphere as CO2. And when those organisms are gone, the soil is no longer naturally fertile and chemical fertilizers become a necessity, not a luxury. But besides going organic - thereby saving the carbon release from soil - there are other simple things you can do with food that will also make a difference:
- Eat locally grown food. If the food doesn't have to travel far, there's less CO2 from the trucks that ship it.
- Eat fruits and vegetables in season. Again, that saves the enormous transportation costs.
- Plant your own vegetable garden. It's not as hard as you might think.
- Eat fresh, not frozen.
9.
Buy recycled. This may sound simple, but it takes less energy to manufacture a recycled product than a brand new one. And before you buy, check to see if the product or its packaging can be recycled. The recyclable logo (three arrows forming a triangle) is fairly common now.
10.
Be a minimalist. Every time you buy something, energy has gone into getting that product to you. So the less you buy, the more you save energy-wise. Buy in bulk. Donate or recycle what you really don't need. Buy quality products that will last longer and reduce quantity.
