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Global Warming

Global Warming

Rising Temperatures

Global warming—a component of climate change—is the rapid increase in recorded temperatures of the ocean, land, and air caused by rising levels of carbon dioxide and other greenhouse gases in the atmosphere.

Discovering the Link

In 1895, a Swedish chemist discovered that by introducing carbon dioxide into the Earth’s environment, humans could make the planet warmer. Over the last century, humanity has tested that hypothesis. As our fossil fuel consumption has accelerated, we’ve released billions of tons of greenhouse gases into the environment—and as predicted by that long-ago chemist, average temperatures have climbed in response. Seven of the top 10 warmest years in U.S. history have occurred since 1998, and the first decade of the 21st century has been the warmest on record since thermometer-based observations began.

How It Happens

In the atmosphere, carbon dioxide (CO2) and other greenhouse gases behave like a giant blanket, trapping and holding the sun’s heat close to the Earth’s surface.

Although carbon dioxide and other greenhouse gases are naturally occurring (produced by bacteria and plants in the soil and oceans), human activities, like the burning of fossil fuels, release an additional 30 billion tons of carbon dioxide into the environment every year.

We’re not just creating more carbon dioxide; we’re also eroding our natural filters for CO2. Trees, for example, “breathe” in carbon dioxide from the air and “exhale” oxygen. When entire forests are destroyed—a process known as deforestation—the carbon dioxide those trees would have processed remains in the atmosphere, compounding the problem. Agricultural practices also affect carbon dioxide levels. For example, weed-management techniques used in industrial agriculture release carbon dioxide that had been locked in the soil.

A Few Degrees Make a Difference

A single degree might not seem like a big deal—who notices when the temperature goes from, say, 64 to 65 on any given afternoon? But when the average global temperature rises by even one degree, it has profound implications for the natural world. Global humidity levels shift, the dates of first and last frosts migrate, the timing of plant flowering and pollinator activity changes. And as temperatures rise, prevailing wind and precipitation patterns shift, transforming weather patterns around the world to produce both drought and flooding. It’s all happening faster than plants and animals can adapt. As the ecological balance forged over millennia goes haywire, it transforms everything from global patterns of human disease spread by insects to the survival of plants and animals.

In Context

Over millennia, average temperatures have risen and fallen—slowly. During the last century, however, the rate of change has accelerated exponentially. Scientists currently project that average global temperatures will continue to increase, perhaps by 2 degrees to 11.5 degrees Fahrenheit before the year 2100. Even if greenhouse gas emissions slow, we can still expect more frequent and more intense heat waves. Throughout the southern United States, that could translate to a doubling of days per year with a temperature above 90 degrees Fahrenheit—from 60 days each year to as many as 150.

Cool Solutions

Internationally, China is the single largest contributor of global greenhouse gas emissions. Winning the silver medal: the United States. In the United States, the single largest contributor to greenhouse gas emissions is electricity production, through the burning of fossil fuels such as coal.

To reduce emissions, U.S. policy has promoted enhanced efficiency of energy plants, the adoption of renewable energy sources, and the purchase of more efficient household appliances, light bulbs, and the like by consumers. Emissions from the transportation industry almost match those of electricity production, so transportation policy—the promotion of walkable communities, bike lanes, efficient mass transit, and increases to fuel efficiency of gasoline-powered vehicles—has the potential to substantially reduce greenhouse gas emissions.

Conventionally raised livestock—beef cattle, especially—contribute substantially to greenhouse gas emissions. The Meatless Monday campaign promotes both personal health and the health of the planet through a once-a-week embrace of a vegetarian diet.

One of the most powerful actions an individual can take to combat global warming is voting for representatives who pursue policies to limit greenhouse gas emissions. Day-to-day choices also add up: Reduce consumption by switching off the lights when you leave a room and insulating your water heater. Choose energy-efficient appliances (look for the Environmental Protection Agency’s ENERGY STAR label), turn down the thermostat or air conditioning at night to reduce energy use, and walk, bike, or take mass transportation whenever possible.



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