The Earth's average temperature IS rising, as the average temperature has increased by about 1 degree Fahrenheit (0.6 degrees Celsius) around the world.
More evidence that the Earth's average temperature has increased recently can be seen in the spring ice thaw and fall ice freeze: The spring ice thaw in the Northern Hemisphere occurs 9 days earlier than it did 150 years ago, while the fall ice freeze begins 10 days later than it used to.
Since weather record-keeping began in the mid-1800s, the 1990s was the warmest decade recorded. The hottest years include 1998, 2002, 2003, 2001, and 1997.
The multinational Arctic Climate Impact Assessment (ACIA) report has recently concluded that average temperatures in Alaska, western Canada, and eastern Russia have increased by 4-7 degrees Fahrenheit (3-4 degrees Celsius) in the last 50 years, which is nearly twice the global average.
In the U.S.'s northernmost city, Barrow, Alaska, the average temperature has increased by over 4 degrees Fahrenheit (2.5-3 degrees Celsius) in just the last 30 years.The United Nations' Intergovernmental Panel on Climate Change (IPCC) is projecting that global temperatures will rise another 3-10 degrees Fahrenheit (1.6-5.5 degrees Celsius) by the end of the 21st century.
Rising temperatures have caused Arctic Sea ice to shrink by nearly 30% since 1978, and it has also thinned the remaining ice as well. ACIA predicts that at least half of the Arctic's summer sea ice will melt by 2100, and that the Arctic region will increase in temperature by 7-13 degrees Fahrenheit (4-7 degrees Celsius) during that same time span.
Greenland's massive ice sheet has enough melt water to raise the sea level by about 23 feet (about 7 meters.) ACIA projects that that sheet will experience significant melting throughout the 21st century.
Large amounts of the Earth's fresh water supply is tied up in the world's many melting glaciers.
Montana's Glacier National Park had 150 glaciers when it was created in 1910; in the early 21st century, it now has less than 30 greatly shrunken glaciers. Tropical glaciers have been reduced even more, as evidenced by Tanzania's Mount Kilimanjaro - its 19,340-foot (5,895-meter) peak has melted by around 80% since 1912 and could be totally gone by 2020.According to the IPCC, the average global sea level has risen 4-8 inches (10-20 cm) over the past 100 years. Their 2001 report is projecting that sea levels could rise anywhere from 4 to 35 inches (10 to 89 cm) by 2100.
This could greatly affect coastal dwellers, as a 1.5 foot (50-centimeter) sea level rise in flat coastal areas would cause a typical coastline retreat of 150 feet (50 meters.) In addition, there are 100 million people worldwide that are living within 3 feet (1 meter) of mean sea level, which means that a rise of just 4 inches (10 centimeters) could promote flooding in many South Sea islands, as well as the U.S. states of Florida and Louisiana.
Global warming could have an effect on the ocean's circulation system, known as the ocean conveyor belt. The conveyor belt moderates global temperatures by moving tropical heat around the planet, but an influx of freshwater from melting ice caps, for example, could cause unforeseen and possibly fast-paced change to the circulation system.
Climate models suggest that global warming could cause more frequent and more extreme weather conditions, including more intense hurricanes and storm surges affecting coastal communities, while heat waves, fires, and drought become more common.
Increased industrialization and shrinking forests since the 1860s have helped raise the atmosphere's carbon dioxide (CO2) level by almost 100 parts per billion, which has led to an increase in Northern Hemisphere temperatures, especially since the 1950s.
In the Arctic, for instance, coastal indigenous communities report shorter periods of sea ice, which no longer temper ocean storms and their destructive coastal erosion. Increased snow and ice melt have raised river levels, while thawing permafrost has caused havoc with roads and other infrastructure. This has forced some communities to move away from historic coastline locations.
Studies show that many European plants are now flowering a week earlier and losing their leaves 5 days later than they did in the 1950s.
Biologists have determined that many birds and frogs are breeding earlier in the season. In addition, a study of 35 non-migratory butterfly species shows that two-thirds of them are now heading 2-150 miles farther north than they did 20 years ago.
There are several signs of global warming in the present day. It is likely that there will be more signs as time passes if we continue in our current ways, which could lead to major changes for all of us in the way we live on Earth.
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