throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the end of the last ice age about 7,000 years ago, at the beginning of human civilization. Most of these climate changes were gradual and attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives .
Sadly, that is not what is happening today. The warming trend we are experiencing has been proceeding at an “unprecedented rate” since the mid-20th century according to NASA, and is “extremely likely” (higher than 95% probability) the result of human activity .
Global warming is a result of an excessive amount of carbon dioxide in the earth’s atmosphere. The amount of carbon dioxide in the atmosphere has risen by 34% since the 17th century. Carbon dioxide, being nearly transparent to solar radiation emitted from the sun, but partially opaque to the thermal radiation emitted by the earth, traps heat in the atmosphere. That is why it has been described as a greenhouse and that is why warming due to excess carbon dioxide trapping heat in our atmosphere is commonly called “the greenhouse effect”.
One indication of global warming is the rising sea level. Globally, the sea level rose about 8 inches in the 20th century. And in the last two decades, the sea has risen at a rate nearly double of the last century. This is because the oceans are absorbing more than 90% of the increased heat caused by carbon dioxide emissions from human activity. This increased heat causes the water to expand. Secondly, it is rising due to ice melting from glaciers and ice sheets .
But what is causing such a dramatic increase in greenhouse gas emissions in the first place?
The greatest contributors to climate change
- Fossil fuels
- Manufacturing and construction
A case in point of just the opposite being true is WRI’s study of Midwest pulp and paper mills, finding that facilities could save $240 million per year in total energy costs by improving their performance to existing ENERGY STAR® levels. These savings could help preserve the 370,000 jobs associated with Midwest pulp and paper mills .
Deforestation for agriculture land use means the forests can no longer absorb the carbon dioxide. And although organic agriculture can remove from the air and sequester 7,000 pounds of carbon dioxide per acre per year , industrial agriculture land farmed with pesticides and fertilizers cannot. Two of the biggest culprits in the agriculture sector making headlines today for inordinate releases of another greenhouse gas, methane, are the cattle industry in the United States and the rice paddies in Asia.
Widespread changes in personal consumer choices could significantly affect the agriculture contribution to global warming. Buying locally translates into reduced emissions from transportation. Eating organic food will reduce demand for food that is grown using heavily polluting modern industrial practices. Reducing meat and rice consumption will reduce the demand for two products that contribute heavily to greenhouse gas emissions.