Energy and Planet Earth
by: Paul Kando
Our world is heating up and the rate of warming has been accelerating. To find out why, scientists have examined the three factors that could be responsible: (1) The sun, (2) Earth's reflectivity, and (3) Greenhouse gases.
Increased incoming solar radiation would warm up the Earth. But, according to the International Panel on Climate Change (IPCC), the sun accounts for only a small portion of warming since 1750 and changes in the sun since 1985 should have cooled the planet. Yet global temperatures have been rising. So the sun is not the cause of global warming.
It's not Earth's reflectivity either. Of the solar energy reaching Earth about 30% is reflected back into space. Changes in how much sunlight is absorbed or reflected, can affect global temperatures. However, satellite and land-based observations and computer models suggest that human-produced particulate pollution has had a cooling effect on the climate. A slight drop in global temperature between 1945 and 1975 was likely the result of rising particulate pollution. Warming resumed after 1975 when the industrialized West began to clean up its particulate pollution while continuing to increase greenhouse gas emissions. Human land use changes since 1750, e.g. forest clearing for agriculture, have, on balance, brightened the planet, producing a cooling effect, yet we had warming. More frequent volcanic eruptions, which can send reflective particles into the stratosphere, cannot explain the observed warming trend either.
That leaves the greenhouse effect as the only remaining scientific explanation. Direct measurements of atmospheric carbon dioxide (CO2) concentrations go back more than 50 years and air bubbles trapped in ice cores have preserved the record of thousands of centuries. Over the past 800,000 years natural CO2 concentrations fluctuated between 180 to 300 parts per million (ppm). Today's levels exceed 390 ppm. The amount of CO2 in the atmosphere is greater now than at any time in measurable history, and it is predicted to increase dramatically this century. Furthermore a unique chemical "fingerprint" proves that the additional CO2 comes mainly from coal and oil.
Carbon dioxide is not the only greenhouse gas of course, but it is the most pervasive remains in the atmosphere for hundreds of years. There is now 60% more CO2 in the atmosphere that at any time within the last 160,000 years. While most atmospheric CO2 is not anthropogenic, we contribute enough to upset the balance and cause warming, mainly by fossil fuel burning and the wholesale removal of CO2 sequestering trees.
Methane (CH4), the next most plentiful greenhouse gas. Its volume is 390% greater than it has been over the last 160,000 years. It remains in the atmosphere for only 12 years, but has 25 times the warming impact of CO2. CH4, a the key ingredient of natural gas, is the subject of an upcoming column.
Additional greenhouse gases include:
- Nitrous oxide (N2O) - laughing gas -, up 18% compared with the last 160,000 years. It remains in the atmosphere 114 years, with 310 times the warming impact of CO2;
- Hydro-fluorocarbons (HFCs), gases used in refrigeration and air conditioning, are known as super greenhouse gases because of their growing utilization and high global warming potential. HFCs remain in atmosphere for only 14 years, but have 3,830 times the warming impact of CO2;
- Perfluorated compounds (PFCs) are used in many important industrial applications. They have up to 7,390 times the warming impact of CO2 and remain in atmosphere for up to 50,000 years.
- Sulfur hexafluoride (SF6), the most potent greenhouse gas evaluated by the IPCC, remains in atmosphere for 3,200 years and has 22,800 times the warming impact of CO2. Fortunately relatively small amounts of SF6 are released, so its contribution to global warming is estimated to be only about 0.2 percent. In Europe, SF6 is banned, except in high-voltage switchgear.
- Water vapor is the most plentiful greenhouse gas of all. Its atmospheric presence is both a cause and a consequence of global warming. The more the planet warms, the more water evaporates and the more vapor in the atmosphere, the more the planet warms - a classic example of positive feedback.
Sadly, none of this is news. That continued fossil fuel use would increase
atmospheric carbon concentrations and warm the planet, was first predicted in 1896
by Svante Arrhenius, the 1903 Nobel laureate in chemistry. Greenhouse gases and
global warming are essentially byproducts of our capitalist/industrial economy.
They are externalities - responsibilities sloughed off onto the commons by private
interests, without compensation and without regard to the damage they cause. In
the end they make our economic system - or life on Earth - unsustainable. The choice
is stark. Unless we act, the implications are obvious. To quote Albert Einstein,
the world is a dangerous place, not because of those who do evil, but because
of those who look on and do nothing.