This has been a crazy year, weather-wise. Hurricanes Katrina, Rita, and Wilma brought widespread devastation. Closer to home, we had January’s blizzard, and October’s torrential rains and flooding.

Down in Mexico, Isla Mujeres, my family’s winter retreat, was walloped by Hurricane Wilma. We’ve been glued to the island’s message board, getting news about our friends and favorite places there, and finding out how we can help.

Has the weather always been this tumultuous? Did we just not notice before? Is this kind of weather going to continue? Are we just having a bad year?

Trying to make sense of this year’s natural disasters (including last December’s tsunami, major floods across Asia, and Pakistan’s recent earthquake), a friend of mine compared our planet to a dirty, wet, shaggy dog. She said the dog is so fed up with its burdens that it has to shake out its fur to lighten its load. War, famine, torture, water and air pollution, government corruption, reliance on fossil fuels, rampant selfishness . . . the planet, she says, is saying “Enough!”

Perhaps she’s right. Could we humans be contributing to changes in climate and weather? To find out, I did some research on Global Warming.

Much of the information available about Global Warming pitches radically in one political direction or another. There are lunatics on both sides of the argument. Either it’s the end of the world as we know it, or it’s a myth created by environmentalists to bring down Big Oil and capitalism. To compound the confusion, Global Warming is not a very simple or straightforward phenomenon, so explanations are often weighted so heavily with scientific jargon that the average reader just gets lost or gives up. I’ve tried to make some sense of it – for myself, and for those who read this column and perhaps share some of my questions.

The concept of global warming refers primarily to changes in climate on our planet. While weather is a temporary state, relating to a specific area, climate is a much more long-term, planet-spanning concern. Climate is calculated by measuring the average weather of the entire globe over a period of centuries.

Speaking in terms of geologic time, the Earth’s climate has changed dramatically. Paleoclimatologists posit that the average temperature has at times been 10 degrees cooler and 20 degrees warmer than it is currently. There are a number of natural factors that affect the earth’s climate, such as variations in our planet’s orbit around the sun, the shifting positions of the continents on earth (as tectonic plates move), the relative power of the sun, volcanic eruptions, and more. But do humans also exert an effect on the climate?

Comprehensive records of the earth’s climate go back only about 100 years. However by studying coral reefs, tree rings, ice cores and lake sediments, climatologists can estimate the earth’s climate as far back as 1000 years. In those ten centuries, the past 100 or so years indicate a major shift in the rate of climate change on earth. Since 1900 the average global temperature has increased about 1 degree F. Most of that warming has occurred in the last 20 years. While this might not seem like a big deal to us, but the experts see it as a relatively rapid increase, especially compared to the earth’s other natural changes.

According to US Environmental Protection Agency (EPA), this one-degree change in climate has produced the following results. “The snow cover in the Northern Hemisphere and floating ice in the Arctic Ocean have decreased. Globally, sea level has risen 4-8 inches over the past century. Worldwide precipitation over land has increased by about one percent. The frequency of extreme rainfall events has increased throughout much of the United States.”

The big problem, experts agree, is the Greenhouse Effect. There are naturally occurring gases in our atmosphere, such as carbon dioxide, methane, nitrous oxide and water vapor. These gases help keep the earth’s temperature comfortable by trapping the sun’s infrared radiation that would otherwise escape into space. The gases retain heat in our atmosphere the way glass panels work in a greenhouse. If not for their presence in the atmosphere, the earth’s temperature would average out to zero degrees F instead of where it is now, about sixty. However if the amounts of these gases get out of hand, dramatic changes can occur. The planet Venus, for example, has an atmosphere comprised almost entirely of carbon dioxide – the CO2 traps so much of the sun’s radiation that that planet is unbearably hot.

Carbon dioxide is the primary concern. A major by-product of the burning of fossil fuels such as oil, coal and gas, carbon dioxide levels in our atmosphere have increased dramatically since the Industrial Revolution. The more carbon dioxide in the atmosphere, the more heat is trapped there. And more heat trapped in the atmosphere results in an increase in global temperatures. It doesn’t matter where the carbon dioxide is produced – it only takes 18 months for it to spread throughout the atmosphere.

While carbon dioxide certainly occurs naturally (humans exhale it with each breath), these days most of it is produced by cars, factories and electrical and other energy plants. Before we started using so much fossil fuel, the amount of carbon dioxide produced by humans was kept in check by the amount absorbed by plants. But that’s no longer the case.

The EPA says, “Increasing concentrations of greenhouse gases are likely to accelerate the rate of climate change. Evaporation will increase as the climate warms, which will increase average global precipitation. Soil moisture is likely to decline in many regions, and intense rainstorms are likely to become more frequent. Sea level is likely to rise two feet along most of the U.S. coast.”

So here’s the answer to my question. Can humans change the weather? Yes. Our actions, especially the by-products of the fossil fuels we burn, directly affect the climate. And as the climate changes, so does the weather.

Is this a problem? Also yes. Unless you enjoy hurricanes and the devastation they bring.

So what can we do? As a global culture, we need to decrease our reliance on fossil fuels. This will not happen overnight. Across the globe, much of economy is based on the use of oil and gas. What would cities be like without these cheap, reliable sources of energy? But over the next hundred years, such change is certainly possible. Let’s support efforts to find alternative sources of energy.

“Strange Days on Planet Earth” DVD series from National Geographic

By Kezia Bacon-Bernstein, Correspondent
October 2005

Kezia Bacon-Bernstein’s articles appear courtesy of the North and South Rivers Watershed Association, a local non-profit organization devoted to the preservation, restoration, maintenance and conservation of the North and South Rivers and their watershed. For membership information and a copy of their latest newsletter, contact NSRWA at (781) 659-8168.