Global Warming

What is global warming?

Global warming refers to an increase in the Earth's temperature, which in turn causes changes in climate. Global warming is the increase in the average temperature of the Earth's air near the surface and the average temperature of the Earth’s oceans in recent decades and its predictable persistence. The Intergovernmental Panel on Climate Change (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations" by the use of the greenhouse effect. Natural incidents such as solar variations combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward. These basic conclusions have been certified by at least 30 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries. While individual scientists have voiced disagreement with some findings of the IPCC, the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.

The greenhouse effect.

The atmosphere has a natural supply of "greenhouse gases." They capture heat and keep the surface of the Earth warm enough for life to thrive. Without the greenhouse effect, the planet would be an uninhabitable, frozen wasteland. Before the Industrial Revolution, the amount of carbon dioxide (CO2) and other greenhouse gases released into the atmosphere was in a rough balance with what could be stored on Earth. Natural emissions of heat-trapping gases matched what could be absorbed in natural sinks. As an example, plants take in carbon dioxide (CO2). When they grow in spring and summer, and release it back to the atmosphere, when they decay and die in fall and winter.

When the industry took off in the mid-1700s, people started emitting large amounts of greenhouse gases. Fossil fuels were burned more and more to run our cars, trucks, factories, planes and power plants, adding to the natural supply of greenhouse gases. These gases can stay in the atmosphere for at least fifty years and up to centuries. There are building up beyond the Earth's capacity to remove them and, in effect, creating an extra thick heat blanket around the Earth. The result to this is that the globe has heated up by about one degree Fahrenheit over the past century, and it has heated up more intensely over the past two decades.

Though one degree may not sound like a lot, think about the fact that the difference in global average temperatures between modern times and the last ice age, when much of Canada and the northern United States of America were covered with thick ice sheets, was only about 9 degrees Fahrenheit. So in fact one degree is very significant, especially since the unnatural warming will continue as long as extra greenhouse gases are put in the atmosphere.

Causes of global warming.

The major causes of climate change and global warming are ocean circulation, the greenhouse effect, volcano eruptions, orbital eccentricity, and aerosols. The oceans play an important role in determining the atmospheric concentration of carbon dioxide (CO2). Carbon dioxide (CO2) gas in the atmosphere and carbon dioxide (CO2) dissolved in the ocean surface reach a balance. Changes in ocean circulation, chemistry, and biology have shifted this balance in the past. Such changes may affect climate by slowly moving carbon dioxide (CO2) into or out of the atmosphere.

Cold water sinks at the poles and travels throughout the world's oceans. It gradually warms, becomes less dense and mixes to the surface. It then moves back towards the poles carrying heat absorbed along the way. Then the cycle continues. Without this cycle the poles would be colder and the equator would be warmer.

A volcanic eruption may send ash and sulfuric acid (SO2) into the atmosphere. A volcanic eruption will increase planetary reflectivity. This will cause atmospheric cooling. Over time precipitation will remove these aerosols from the atmosphere. Volcanic eruptions can have a worldwide impact.

The Earth's orbital path varies in the degree to which it is circular. This change in its "eccentricity" varies between 0.00 and 0.06 on a 100,000 year cycle. When the eccentricity equals 0.00 the orbital path is circular and when it is 0.06 the orbital path is slightly elliptical. The current value is 0.0167.

Aerosols can have different effects. Different types of small particles can have either warming or cooling effects. Sulfate aerosols released by volcanoes reflect sunlight and cool the Earth. Black dust released by smoke stacks and wild fires absorbs solar radiation and can warm the Earth. Aerosol concentrations change for many reasons, including volcanic eruptions, spread of fires, increased windiness, drying of damp soils, changes in industrial processes, and more. Accurately projecting the extent and effect of aerosols is one of the major challenges in modeling the future of climate change.