The Greenhouse Effect and Global Warming
(in Simple English)

(c) 2010 by Barton Paul Levenson

Maybe you want to understand the whole global warming thing, but you hate math. Or you just want a simple, clear explanation without a lot of confusing science jargon thrown in. If so, maybe this page will help.

The Greenhouse Effect, and Global Warming, in Simple English

In 1824, Jean-Baptiste Fourier realized the sun does not give us enough heat to keep Earth as warm as it is. It could only heat us to 254 K. Water freezes at 273 K. If we depended on sunlight alone, Earth would be frozen over. But Earth's surface temperature averages 288 K. Fourier thought the atmosphere must act as a blanket to retain Earth's heat, but he didn't understand how. He thought it might involve infrared radiation--IR--which he called "chaleur obscure" ("dark heat").

In 1858, John Tyndall found that certain "greenhouse gases" in the air let sunlight through, but absorb IR from the ground. They heat up, and radiate IR of their own. Some of that goes back down to Earth--so Earth has both sunshine and "atmospheric back radiation" heating it. That solved Fourier's problem. Tyndall identified water vapor and carbon dioxide as the two most important greenhouse gases.

In 1896, Svante Arrhenius studied what would happen with different levels of greenhouse gases in the air. He wanted to understand what had caused the ice ages. He found doubling Earth's CO₂ would raise the surface temperature 5.5 K. Since civilization back then got its power mainly from burning coal, doubling was inevitable sooner or later. He guessed that might take about 3,000 years.

In 1901, Knut Angstrom and his assistant, J. Koch, thought they had disproved Arrhenius's theory. They shone IR through a tube of compressed CO₂ equal to a column of Earth's whole atmosphere. Then they tried it with 1/3 more CO₂. There was no noticeable difference in absorption. The absorption lines of CO₂ were "saturated," they said, so adding more couldn't warm the Earth.

For decades scientists accepted this. But high-altitude observations made during World War II showed CO₂ was NOT saturated at higher atmospheric levels, where pressure and temperature were lower. And IR absorption from all levels matters, not just from the ground. Angstrom was wrong.

In 1956, Gilbert Plass published the first quantitative estimate of global warming using a computer. He found doubling CO₂ would increase temperatures 3.6 K.

In 1958, Charles Keeling and Roger Revelle established the observatory at Mauna Loa, Hawaii. One of the first things they found from flask sampling was that the level of CO₂ in the air rose every year. It would not take 3,000 years to double.

In 1964, Manabe Syukuro and Robert Strickler wrote the first "radiative-convective model" of Earth's atmosphere. Climatologists and astronomers all over the world now use these models. Manabe and Strickler predicted a 2.4 K rise from doubled CO₂.

More predictions followed, usually finding figures from 2-4 K for CO₂ doubling. People paid little attention, since there was slight cooling in the 1940s, and even temperatures through the '60s. Steven Schneider even suggested a new ice age might come prematurely.

But in 1975 temperatures started rising. In 1988, James Hansen testified to Congress that "the greenhouse effect is here." Industry immediately kicked its propaganda machine into high gear. It was too early to tell, they said. Not all scientists agreed about global warming. We didn't need more regulation. Exxon-Mobil, Koch Oil, Consolidated Coal, and other companies gave millions to right-wing think tanks and pseudoscience crackpots who claimed global warming was not happening and would not be a problem if it were.

But by 1990, the majority of climate scientists--97% in the latest survey--were convinced. Weather stations, sea surface samples, balloon radiosondes, boreholes, and satellites all showed temperatures rising. Greenland and Antarctica lost ice mass. Arctic sea ice shrank. The eggs of insects, fish, frogs, and birds hatched earlier and earlier. Tree lines moved toward the poles and up mountains. Glaciers receded. Flowers bloomed earlier each year.

Was this a problem? Who wouldn't want warmer temperatures? Shovel less snow out of the driveway each year? Sign me up!

But the probable consequences were horrifying. As ice melted and water expanded, the seas would rise, eventually drowning coastal cities, destroying trillions of dollars' worth of infrastructure, and making hundreds of millions of refugees. The countries of Bangladesh and Tuvalu would be under water. So would half of Florida.

But that might take centuries. Other dangers were closer. Global warming moves the rain. Continental interiors dry out, while storms soak the coasts. Both effects hurt crops.

I studied this effect, and found out how global warming affected drought. If CO₂ rose without restraint--"business as usual"--the severe-drought fraction would hit 70% by 2056. No country in the world would have a good harvest. Human civilization would collapse.

World food stores are a nice, Biblical number--about forty days. A year after the harvests fail, most people will be dead. It may be a thousand years before there's civilization on Earth again.

And we've already used all the easily available metal, fossil fuels, and plant-derived drugs. The mass extinction now underway can only get worse. Can we build a civilization without horses? Or cattle? Or with dead oceans? Ocean acidification from rising CO₂ has already killed 25% of the world's corals. Ninety percent of the big game fish--tuna, swordfish, Atlantic cod--are gone. Worse, 40% of the phytoplankton have disappeared since 1950.

Phytoplankton are the base of the ocean food chain. A billion people need fish as a staple. No phytoplankton, no fish.

Another billion get fresh water from glaciers. Nuclear-armed India and Pakistan have already exchanged shots and had troops killed over which side owns a glacier. China wants the Siachen glacier region, too. They also have nukes.

Will humanity wise up in time? Switch away from fossil fuels ASAP? Go to all solar, wind, geothermal, and biomass?

What do you think?