GLOBAL WARMING

Global warming was once an uncommon term used by a few scientists who were growing concerned over the effects of decades of pollution on long-term weather patterns. Today, the idea of global warming is well known, if not well understood. It is not unusual to hear someone complaining about a hot day or a freak storm and remark: "It's global warming."

Well, is it?

What actually is "global warming"?

What actually is global warming? What causes it? What are its effects? Is it something we need to worry about?

Global warming is a significant increase in the Earth's climatic temperature over a relatively short period of time as a result of the activities of humans.

In specific terms, an increase of 1 or more degrees Celsius in a period of one hundred to two hundred years would be considered global warming. Over the course of a single century, an increase of even 0.4 degrees Celsius would be significant.

What are the effects of climate change?

Even small changes in climate can have major effects. When scientists talk about "the Ice Age," you probably envision the world frozen, covered with snow and suffering from frigid temperatures. In fact, during the last ice age (ice ages recur roughly every 50,000 to 100,000 years), the earth's average temperature was only 5 Celsius degrees cooler than modern temperature averages [Source: NASA].


Is the earth warming up?

The Intergovernmental Panel on Climate Change (IPCC), a group of over 2,500 scientists from countries across the world, convened in Paris in February, 2007 to compare and advance climate research. The scientists determined that the Earth has warmed 0.6 degrees Celsius between 1901 and 2000. When the time frame is advanced by five years, from 1906 to 2006, the scientists found that the temperature increase was 0.74 degrees Celsius.

Any concrete evidence of this temperature increase?

Yes, lots of evidence. The IPCC has observed:
# Of the last 12 years, 11 have ranked among the warmest years since 1850.
# The warming trend of the last 50 years is nearly double that of the last 100 years, meaning that the rate of warming is increasing.
# The ocean’s temperature has increased at least to depths of 3,000 meters (over 9,800 feet); the ocean absorbs more than 80 percent of all heat added to the climate system.
# Glaciers and snow cover have decreased in regions both in the Northern and Southern hemispheres, which has contributed to the rise of sea levels.
# Average Arctic temperatures increased by nearly twice the global average rate over the last 100 years (the IPCC also noted that Arctic temperatures have are highly variable from decade to decade).
# The area covered by frozen ground in the Arctic has decreased by approximately 7 percent since 1900, with seasonal decreases of up to 15 percent.
# Precipitation has increased in eastern regions of the Americas, northern Europe and parts of Asia; other regions such as the Mediterranean and southern Africa have experienced drying trends.
# Westerly winds have been growing stronger.
# Droughts are more intense, have lasted longer and covered larger areas than in the past.
# There have been significant changes in extreme temperatures – hot days and heat waves have become more frequent while cold days and nights have become less frequent.
# While scientists have not observed an increase in the number of tropical storms, they have observed an increase in the intensity of such storms in the Atlantic correlated with a rise in ocean surface temperatures.


The Greenhouse Effect


Global warming is caused by an increase in the greenhouse effect. The greenhouse effect is not a bad thing by itself -- it's what allows Earth to stay warm enough for life to survive.




When the sun's rays hit the Earth's atmosphere and the surface of the Earth, approximately 70 percent of the energy stays on the planet, absorbed by land, oceans, plants and other things. The other 30 percent is reflected into space by clouds, snow fields and other reflective surfaces [Source: NASA].


But even the 70 percent that gets through doesn't stay on earth forever (otherwise the Earth would become a blazing fireball). The Earth's oceans and land masses eventually radiate heat back out. Some of this heat makes it into space. The rest of it ends up getting absorbed when it hits certain things in the atmosphere, such as carbon dioxide, methane gas and water vapor. After these components in our atmosphere absorb all this heat, they emit energy (also in the form of heat).

The heat that doesn't make it out through Earth's atmosphere keeps the planet warmer than it is in outer space, because more energy is coming in through the atmosphere than is going out. This is all part of the greenhouse effect that keeps the Earth warm.

Earth Without the Greenhouse Effect

What would Earth look like if there weren't any greenhouse effect at all? It would probably look a lot like Mars. Mars doesn't have a thick enough atmosphere to reflect enough heat back to the planet, so it gets very cold there.

Global Warming: What's Happening?

The greenhouse effect happens because of certain naturally occurring substances in the atmosphere. Unfortunately, since the Industrial Revolution, humans have been pouring additional huge amounts of those substances into the air.

Carbon dioxide (CO2) is a colorless gas that is a by-product of the combustion of organic matter. It makes up less than 0.04 percent of Earth's atmosphere, most of which was put there by volcanic activity very early in the planet's life. Today, human activities are pumping huge amounts of CO2 into the atmosphere, resulting in an overall increase in carbon dioxide concentrations.

What is the consequence of this increase in carbon dioxide concentrations?

These increased concentrations are considered the primary factor in global warming, because carbon dioxide absorbs infrared radiation. Most of the energy that escapes Earth's atmosphere comes in this form, so extra CO2 means more energy absorption and an overall increase in the planet's temperature.

The Worldwatch Institute reports that carbon emissions worldwide have increased from about 1 billion tons in 1900 to about 7 billion tons in 1995. The Institute also notes that the average surface temperature of Earth has gone from 14.5 degrees C in 1860 to 15.3 degrees C in 1980.


The IPCC says that the pre-industrial amount of CO2 in the Earth's atmosphere was about 280 parts per million (ppm), meaning that for every million molecules of dry air, 280 of them were CO2. In contrast, 2005 levels of CO2 were measured at 379 ppm [Source: IPCC].

Any other problem causing pollutant?

Nitrous oxide (NO2) is another important greenhouse gas. Although the amounts being released by human activities are not as great as the amounts of CO2, nitrous oxide absorbs much more energy than CO2 (about 270 times as much). For this reason, efforts to curb greenhouse gas emissions have focused on NO2 as well [Source: Soil Conservation Council of Canada]. The use of large amounts of nitrogen fertilizer on crops releases nitrous oxide in great quantities, and it is also a by-product of combustion.

The danger from global warming:

What will actually happen if the entire planet warms up a few degrees?

We have seen that an average drop of just 5 degrees Celsius over thousands of years can cause an ice age; so what will happen if the Earth's average temperature increases a few degrees in just a few hundred years?

Glaciers and ice shelves around the world are melting [Source: Guardian Unlimited]. An immediate result of melting glaciers would be a rise in sea levels. Initially, the rise in sea level would only be an inch or two. Even a modest rise in sea levels could cause flooding problems for low-lying coastal areas. However, if the West Antarctic Ice Sheet were to melt and collapse into the sea, it would push sea levels up 10 meters (more than 32 feet), and many coastal areas would completely disappear beneath the ocean [Source: NASA].

What are the dangers to humans?

The human cost of global warming is hard to quantify. Thousands of lives per year could be lost as the elderly or ill suffer from heat stroke and other heat-related trauma. Poor and underdeveloped nations would suffer the worst effects, since they would not have the financial resources to deal with the problems that come with an increase in temperature. Huge numbers of people could die from starvation if a decrease in precipitation limits crop growth and from disease if coastal flooding leads to widespread water-borne illness.

The Carnegie Institution estimates that around $5 billion in crop losses per year are due to global warming. Farmers see a decrease of about 40 million metric tons of cereal grains like wheat, barley and corn each year. Scientists discovered that an increase of 1 degree Fahrenheit in average temperature results in a 3 to 5 percent drop in crop yields [Source: Science Daily].

Can We Stop Global Warming?

Though scientists warn that global warming will likely continue for centuries because of the long natural processes involved, there are a few things we can do to decrease the effects. Basically, they all boil down to this: Don't use as much of the stuff that creates greenhouse gases. On a local level, you can help by using less energy. The electricity that operates many of the devices in our homes comes from a power plant, and most power plants burn fossil fuels to generate that power. Turn off lights when they're not in use. Take shorter showers to use less hot water. Use a fan instead of an air conditioner on a warm day.


Any other ways to help decrease greenhouse-gas emissions?


Here are some other specific ways you can help decrease greenhouse-gas emissions:
# Make sure your car is properly tuned up. This allows it to run more efficiently and generate fewer harmful gases.
# Walk or ride your bike if possible, or carpool on your way to work. Cars burn fossil fuel, so smaller, more fuel-efficient cars emit less CO2, particularly hybrid cars.
# Turn lights and other appliances off when you're not using them. Even though a light bulb doesn't generate greenhouse gas, the power plant that generates the electricity used by the light bulb probably does. Switch from incandescent light bulbs to fluorescent bulbs, which use less energy and last longer.
# Recycle. Garbage that doesn't get recycled ends up in a landfill, generating methane. Recycled goods also require less energy to produce than products made from scratch.
# Plant trees and other plants where you can. Plants take carbon dioxide out of the air and release oxygen.
# Don't burn garbage. This releases carbon dioxide and hydrocarbons into the atmosphere.

The need for non-fossil fuel energy sources

To really stem the emission of greenhouse gases, we need to develop non-fossil fuel energy sources. Hydro-electric power, solar power, hydrogen engines and fuel cells could all create big cuts in greenhouse gases if they were to become more common.

The Kyoto treaty

At the international level, the Kyoto treaty was written to reduce CO2 and other greenhouse gas emissions worldwide. Thirty-five industrialized nations have committed to reducing their output of those gases to varying degrees. Unfortunately, the United States, the world's primary producer of greenhouse gases, did not sign the treaty.