Global warming is shorthand for “climate change” and the term is correct if you realize that it’s referring to the average temperature of the Earth over years and decades; not to the temperatures at particular times and places.
“Climate change” is a much better term because much more than warming is involved, although the changes first begin with the globe’s average warming. This average warming can cause changes in patterns of rainfall. It can lead to more snow piling up in places such as Antarctica and Greenland, and it can even include some parts of the Earth growing colder.
Scientists have managed to figure out a general, fairly detailed picture of the Earth’s climate going back more than 100,000 years, before the beginning of the last ice age.
This history shows that temperatures of different parts of the Earth, and even the Earth’s average temperature, have swung widely in the past into and out of ice ages, long before humans could have affected the climate.
Still, climate scientists say the evidence is strong that humans are responsible for much of the warming since early in the 20th century.
There’s no doubt that the amount of carbon dioxide in the air — a “greenhouse” gas — has increased. This increase in a greenhouse gas is bound to “force” the climate in one direction or another with a general warming being one of the effects.
Climate scientists also have strong reasons for saying that as humans continue adding gasses to the air, warming is likely to continue through this century.
Many questions remain to be answered. These include how much of the warming to date has been caused by humans, how much is natural. Only estimates offering wide ranges of how much the climate should warm during this century are available.
Many questions remain about the effects of a generally warmer climate.
While climate scientists don’t agree on all of the points made, a recent report issued by working groups (or committees) of the Intergovernmental Panel on Climate Change (IPCC) is the best place to begin understanding the current state of climate change science. The IPCC, which is made up of scientists from 113 countries, was created by the U.N. in 1988 and releases its assessments every five or six years.
The report by the world’s top climate scientists said global warning was “very likely” man-made and would bring higher temperatures and a steady rise in sea levels for centuries to come regardless of how much the world slows or reduces its greenhouse gas emissions. “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widspread melting of snow and ice, and rising global mean sea level,” said the IPCC report.
Here are some of the primary findings of the IPCC report:
THE CAUSE: Global warming is “very likely” caused by man, the strongest conclusion to date.
THE OUTLOOK: Now that the world has begun to warm, hotter temperatures and rises in sea level “would continue for centuries” no matter how much humans control their pollution.
TEMPERATURE CHANGE: The panel predicted temperature rises of 2°F-11.5°F by the year 2100. That was a wider range than in the 2001 report. However, the panel also said its best estimate was for temperature rises of 3.2°F-7.1°F. In 2001, all the panel gave was a range of 2.5°F-10.4°F.
SEA LEVELS: The report projected rises of 7-23 inches by the end of the century. An additional 3.9-7.8 inches are possible if recent, surprising melting of polar ice sheets continues.
HURRICANES: An increase in hurricane and tropical cyclone strength since 1970 “more likely than not” can be attributed to man-made global warming. The scientists said global warming’s connection varies with storms in different parts of the world, but that the storms that strike the Americas are global warming-influenced.
The report notes that no global changes have been noted during the 20th century in terms of the numbers of storms or their strength. “No systematic changes in the frequency of tornadoes, thunder days, or hail events are evident in the limited areas analyzed.”
While snow cover and sea ice in the Northern Hemisphere are expected to continue decreasing, and glaciers should continue retreating, (as they did during the 20th century) the Antarctic ice sheet should grow. This is because warmer air can hold more humidity, which will increase the amount of snow in Antarctica. This in turn, will offset some of the water being added by melting glaciers and some melting of the Greenland ice cap.
You can learn about Global Warming @ Resources: Climate change science, which will take you to many sources of additional information about climate change science.