C A U S E S A N D E F F E C T S O F C L I M A T E C H A N G E
sea levels are rising, cloud forests are dying, and wildlife isscrambling to keep pace. It has become clear that humans havecaused most of the past century’s warming by releasing heat-trappinggases as we power our modern lives. Called greenhouse gases, theirlevels are higher now than at any time in the last 800,000 years. We often call the result global warming, but it is causing a set ofchanges to the Earth’s climate, or long-term weather patterns, thatvaries from place to place.
While many people think of globalwarming and climate change assynonyms,scientists use “climatechange” when describing the complex shifts now affecting ourplanet’s weather and climate systems—in part because someareas actually get cooler in the short term. Climate change encompasses not only rising average temperaturesbut also extreme weather events, shifting wildlife populations andhabitats, rising seas, and a range of other impacts. All of thosechanges are emerging as humans continue to add heat-trappinggreenhouse gases to the atmosphere, changing the rhythms ofclimate that all living things have come to rely on. What will we do—what can we do—to slow this human-caused warming? How will we cope with the changes we’ve already set intomotion? While we struggle to figure it all out, the fate of the Earth aswe know it—coasts, forests, farms, and snow-cappedmountains—hangs in the balance. Understanding the greenhouse effectThe “greenhouse effect” is the warming that happens when certaingases in Earth’s atmosphere trap heat. These gases let in light butkeep heat from escaping, like the glass walls of a greenhouse, hencethe name. Sunlight shines onto the Earth’s surface, where the energy isabsorbed and then radiate back into the atmosphere as heat. In theatmosphere, greenhouse gas molecules trap some of the heat, and therest escapes into space. The more greenhouse gases concentrate inthe atmosphere, the more heat gets locked up in the molecules
Why does this matter?
The rapid rise in greenhouse gases is a problem because it’s changingthe climate faster than some living things can adapt to. Also, a newand more unpredictable climate poses unique challenges to all life. Historically, Earth’s climate has regularly shifted betweentemperatures like those we see today and temperatures cold enoughto cover much of North America and Europe with ice. The differencebetween average global temperatures today and during those ice agesis only about 9 degrees Fahrenheit (5 degrees Celsius), and theswings have tended to happen slowly, over hundreds of thousands ofyears. But with concentrations of greenhouse gases rising, Earth’sremaining ice sheets such as Greenland and Antarctica are starting tomelt too. That extra water could raise sea levels significantly, andquickly. By 2050, sea levels are predicted to rise between one and 2.3feet as glaciers melt. As the mercury rises, the climate can change in unexpected ways. Inaddition to sea levels rising, weather can become more extreme. Thismeans more intense major storms, more rain followed by longer anddrier droughts—a challenge for growing crops—changes in the rangesin which plants and animals can live, and loss of water supplies that have historically come from glaciers.
Priya bala
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