The atmosphere insulates the planet with the help of greenhouse gases. Nitrogen and oxygen make up the majority of Earth’s atmosphere and do not absorb heat. Others such as water vapor, carbon dioxide, ozone, and trace amounts of methane absorb and re-radiate heat bouncing into space from the Earth’s surface, keeping the heat in and keeping the planet much warmer than it would be in their absence.

This effect was first explained the late 1890s by a Swedish scientist, Svante Arrhenius. A failing marriage drove him to spend up to 14 hours a day on laborious calculations as he attempted to solve the mystery of the Earth’s ice ages. Arrhenius noticed that the carbon dioxide in the atmosphere helped the planet retain warmth from the sun, and that humans were adding to the concentration of the gas in the atmosphere by burning coal for energy. He predicted that a doubling of the background level of CO2 would lead to an average temperature increase of 5 degrees Celsius, which is actually quite similar to the estimate currently given by the Intergovernmental Panel on Climate Change. Being a Swede, Arrhenius wasn’t too worried about the added warmth.

Starting in 1958 Charles David Keeling began keeping measurements of CO2 in the atmosphere, from the slope of a volcano on Mauna Loa. His chart shows the persistent increase of the gas from that time to the present day.

Keeling’s research led other scientists to develop methods of measuring the concentration of the gas in the distant past. By analyzing tiny bubbles trapped in arctic ice cores scientists were able to determine that pre-industrial levels of CO2 were near 280 parts per million (ppm). Currently the gas is at a concentration of 380 ppm.

In 1998, scientist Michael Mann published his chart of temperature records that came to be known as the “hockey stick” graph. Using tree ring data from around the globe, Mann’s chart showed the cyclic nature of Earth’s past temperature changes, and the alarming upward trend shown by the past forty years of actual temperature measurements.

The chief scientific body reporting on climate change, the IPCC (whose estimates are generally held to be conservative), has warned that a doubling of the pre-industrial level of CO2 will lead to an increase of average global temperature of 2.5 to 10.4 degrees Fahrenheit. This sounds negligible, but the effects of such an increase could be immense. For perspective, the change in temperature from the coldest point of an ice age to the warmest point of an interglacial period is only 10 degrees.

A daunting task, but not unsurmountable. Richard Socolow, from (UNIV.), has outlined a set of plans that could be implemented right now, with no further technological innovations necessary, to arrive in 2050 at a stable atmospheric concentration of CO2. Each wedge of Socolow’s plan would save one gigaton of the gas over 50 years, and he has developed fifteen or more possible wedges. Implementing only seven of Socolow’s wedges would stabilize greenhouse CO2 levels below a dangerous amount.

The consequences of climate change induced by greenhouse warming include sea-level rise, increased intensity of tropical storms, detrimental shifts in precipitation patterns (causing an increase of floods in wet regions and droughts in dry or marginal regions), and the increased likelihood of such fantastic-seeming scenarios as the shutdown of the gulf stream due to an influx of fresh meltwater, which could plunge northern Europe into a far colder climate.

Concerned scientists and environmentalists around the world have been working together steadily since the early 1990s to craft a global policy solution to the problem of global greenhouse warming. Their efforts have been stymied by the refusal of the largest carbon emitter, the United States, to cooperate. Our country is holding back from the reductions mandated by the Kyoto protocol in protest of the fact that China and India are not held similarly accountable, even though they will soon be producing more of the industrial gases than the US.

Realizing that galvanizing the political will of the citizens of the US to act on reducing greenhouse emissions is the fastest and perhaps the only way to solve the problem, Al Gore has recently embarked on a massive campaign to educate the public. His efforts are probably responsible for most of the attention currently being paid to the issue by American mass-media.

The Good News

This past August the state of California signed legislation that rivals the reductions asked for by the Kyoto protocol. California has a population of 36 million, (which is more than all of Canada, or about five times that of Switzerland), and current greenhouse emissions of around 465 million tons of CO2 equivalents per year (about the same as the emissions of Spain and Denmark combined). The state vows to emit 25% less of the greenhouse gases by 2020, and get to 80% below 1990 levels by 2050, partly by utilizing renewable sources for 20% of their energy portfolio by 2010. Still in court is legislation that would require automobiles sold in California to emit 30% less CO2 by 2016. Ten other states including New York, New Jersey, Massachusetts, Connecticut and Pennsylvania, have said they will follow suit if the law is eventually passed. According to a study from University of California at Berkeley, cutting California's greenhouse emissions to 1990 levels by 2020 could boost the state's economy by $74 billion and create 88,000 new jobs. DuPont has cut its greenhouse gas emissions by nearly 70 percent since 1990, saving about $2 billion. Similarly, IBM has saved nearly $800 million, thanks to its 65 percent cut in its emissions in the same period.

Unfortunately, as nice as this all sounds, it doesn't even scratch the surface when compared with the massive growth in emissions every year in the developing world as automobiles become more affordable and new coal-fueled power plants go online. There are many reasons for hope, but they'll turn into pipe dreams unless we all act, now, to reduce our society's carbon output. Read on to learn how.