To have life on earth, the temperature needs to stay within a certain range.
The atmosphere is like a blanket around the earth. It keeps some of the sun’s heat in and allows some to go back into space.
The atmosphere is made of gases. Some are greenhouse gases such as carbon dioxide, nitrous oxide, methane and hydrofluorocarbons.
Human activity is one source of greenhouse gases. For example, burning fossil fuels, like gasoline in a car, emits carbon dioxide.
As humans increase the amount of greenhouses gases that we emit into the atmosphere, less heat can escape into space.
It allows the sun’s heat to come in, but then traps it inside that blanket, raising the temperature of the planet overall.
For all of history, the earth’s climate and the amount of greenhouse gases have changed. But it always stayed within a certain range.
There is more carbon dioxide in the atmosphere now than at any time in the past 420,000 years.
That’s 380 parts per million. It has never gone above 300 parts per million before.
Scientists measure how greenhouse gases have changed over time. They study it in polar ice cores, ocean sediments and tree rings.
In the past 150 years, levels of these gases have increased by about 25 percent.
Most carbon dioxide emissions come from burning fossil fuels.
The U.S. produces about 25 percent of global carbon dioxide emissions. Eighty-five percent of American energy needs are supplied through burning fossil fuels.
The result? The Intergovernmental Panel on Climate Change (IPCC) reports that the average surface temperature of the earth increased nearly 1.4°F in the 20th century, due primarily to human caused global warming.
In the Arctic and Antarctic, the impacts are even greater.
The global average temperature has risen just over 1 degree Fahrenheit, but in Alaska, it has gone up an average of 4 degrees, and 7-10 degrees in winter.
People who rely on frozen tundra to travel have fewer days because it is melting earlier.
Summer sea ice in the Arctic is melting faster than climate models projected. In 2007, the summer sea ice melt exceeded normal ice melt by a million square miles-- an area equal to the size of Alaska and Texas combined.
United States Geological Survey scientists conservatively project that 2/3rds of the polar bear population in the world could disappear by 2050, including all of Alaska’s polar bears.
Global warming is causing the ice sheets in Greenland and Antarctica to melt. Scientists predict the oceans to rise between 7.8 inches and two feet by 2100, causing millions of people to lose their homes along the coast.
As climate changes, the impact will be different across the globe – wetter and drier, warmer and colder. There will be more water in the atmosphere, intensifying weather.
Large portions of America’s forests are already dying from climate change. High temperatures and drought lead to the death of millions of pinyon trees in the Southwest from bark beetle infestations.
Forests in the western US suffered four times the number of major fires that were experienced just two decades ago.
Although fire is a natural part of many forest ecosystems, the increase in frequency and area burned is depleting soils, increasing erosion that damages streams, and altering natural habitats.
The increased intensity of hurricanes from climate change can also have a huge impact on forests, as happened in Hurricane Katrina, which damaged five million acres of forest and killed or severely damaged 320 million large trees.
Global warming is the single biggest threat to wildlife today.
In its 2007 report, the International Panel on Climate Change stated that 20-30% of species worldwide are likely to be at increased risk of extinction if increases in average global temperatures exceed 2.2-4.0° F above current levels. This could happen by the end of the century if global warming pollution is not dramatically reduced.
Adapted to cold temperatures, moose are being stressed by climate changes. In Minnesota, researchers concluded that climate change was the driving force behind a population crash in 2003.
But we can do something. Scientists have told us that we must reduce global warming pollution by 80% by 2050 to avoid the worst impacts of global warming.
They have set the goal, now we have to set the pace. We can get there by reducing global warming pollution by 2% every year for the next 40 years.
Reducing your global warming pollution by replacing incandescent light bulbs with a fluorescent ones, or planting a tree!
Reducing energy use by 2% per year is an achievable goal. And in 40 years, we will reach our goal of an 80% reduction in global warming pollution – a sustainable legacy for our children.
