![]() That’s 11 degrees colder than the 20th century’s average global temperature. During the Last Glacial Maximum, the planet’s average temperature was around 46 ☏.ĭuring the Last Glacial Maximum, on average, the planet’s temperature hovered around 46☏. Because of all the water locked in frozen ice sheets at the time, the sea level was 400 feet lower than it currently is. Steppes, which are flat, unforested grasslands, expanded across the planet and sub-Saharan Africa became more arid. Other parts of Northern Europe were basically transformed into a tundra, wiping out the warm-weather plants that had previously thrived there. ![]() Ice sheets up to a mile thick covered North America-including a whopping 97 percent of Canada-as well as large parts of Northern Europe, Asia, and Patagonia. Back then, 8 percent of the Earth’s surface, and a quarter of the planet’s total land area, was buried beneath ice. The ice age reached its height, a period called the Last Glacial Maximum, around 20,000 years ago. Ittiz, Wikimedia Commons // CC by SA 3.0 The first of Earth’s five major ice ages was the Huronian glaciation.Īn artist’s interpretation of Earth during the Last Glacial Maximum. This ebb and flow of ice and heat is a long process that plays out over a span of tens of thousands of years, so you can probably cross off an instant planetary freeze, à la 2004’s The Day After Tomorrow, from your list of climate concerns. During an interglacial period, glaciers recede toward the poles but don’t completely disappear. Ice ages go through periods of freezing and thawing.Įach of the major ice ages themselves went through cycles of freezing and thawing, called glacial and interglacial periods. As layers of snow condense into glaciers and ice sheets, they reflect more sunlight-and therefore heat-causing global temperatures to drop. When the angle of Earth’s tilt decreases, summers cool down, allowing snow to accumulate. These changes happen regularly over the course of hundreds of thousands of years, affecting the amount of sunlight that different latitudes on Earth receive, and by extension, the planet’s temperature. The planet’s orbit and the tilt of its axis aren’t as constant as you might think, and variations in them can contribute to ice ages. Changes in the planet’s orbit and tilt can contribute to ice ages.Įarth From Apollo 16. More ambitiously, some believe that human beings could eventually harness certain rocks’ carbon sequestering powers to help combat climate change. At minimum, the slow carbon cycle could give us insights into how the planet regulates its temperature. This is an area of intense interest for geologists and other climate scientists. Anything that exposes new rocky material would therefore lead to increased carbon sequestration. Newer research complicates this picture-it may be that mountain formation doesn’t lead to an increase in weathering overall, but instead exposes rocky material that’s more reactive, and therefore more efficient at weathering rocks and sequestering carbon. Some believe that the formation of these mountains causes increased weathering, which could then allow more carbon from the air to get stored in rocks. ![]() ![]() The formation of large mountain ranges, like the Himalayas, is often at the center of these investigations. That volcano example is a somewhat speedier version of what’s sometimes called the slow carbon cycle, in which carbon moves between rocks, soil, the ocean, and the atmosphere over hundreds of millions of years.īecause rocks can sequester carbon-remove it from the atmosphere and store it in a form that doesn’t contribute to the greenhouse effect-scientists are interested in what factors might slow down or accelerate the weathering processes that break down rocks and lead to this sequestration. It’s believed that all that carbon created acid rain. As geochemist Lee Kump explained to the Earth science publication EOS, when acid rain “‘attacks silicate rocks like granites and basalts,’ a chemical reaction incorporates the CO2 into limestone, which removes the molecule from the atmosphere.” More carbon in rocks and ocean floor sediment and less in the atmosphere might have contributed to the Earth’s cooling. You probably know that increased carbon dioxide levels in the atmosphere can warm the planet, but they might also have the opposite effect, given the right set of conditions.Īround 460 million years ago, the volcanic eruptions that helped create parts of the northern Appalachian Mountains dumped record-breaking amounts of CO2 into the atmosphere. There are a number of factors that might help plunge the planet into an ice age, and some explanations aren’t particularly intuitive. Volcanic eruptions may have led to acid rain, which could have contributed to planetary cooling. ![]()
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