Earth Science: CLIMATE CHANGE
Myriad natural factors help explain the current warming trend in the Earth’s climate, in particular a natural climate cycle that occurs over thousands of years.
However, the speed at which the recent change is occurring is curious and disconcerting. Scientists are exploring the possibility of human activity as one of the influences.
Earth – Atmosphere – Climate Change
Scientists are tackling questions surrounding the causes of recent record high temperatures and a global increase in natural disasters. One possible cause of unusual climate change may be modern-day human activity.
The alternation between cold and warm phases on Earth constitutes a natural cycle. On average, a phase lasts 100,000 years. Within a natural cycle, less significant climate changes occur in cycles of approximately 20,000 and 40,000 years. In 1920, Milutin Milankovitch, a Serbian astronomer and mathematician, realized that astronomical forces have a cyclical influence on the intensity of solar radiation reaching the Earth.
The Earth rotates like a spinning top as it revolves in an elliptical path around the sun. At intervals of 20,000, 40,000, and 100,000 years, this planetary motion determines the distance between the Earth and the sun, and thus the angle at which sunlight strikes the Earth. This may serve as a climate change trigger. Milankovitch cycles are confirmed by data collected from sediments on the ocean floor and from core samples obtained by drilling into polar ice.
At this time Earth is in the midst of a warm phase within an ice age. However, this does not by itself account entirely for recent climate changes. Although it can be assumed that humans are not the sole cause of global warming, the worldwide scientific consensus asserts that human activity since the industrial revolution has certainly influenced the warming process.
Statistically speaking, clusters of storms appear regularly and influence Earth’s natural climate cycles. Researchers predict that such clusters and other extreme weather phenomena, such as the destructive Hurricane Katrina, which hit the U.S. Gulf Coast in 2005, may become more common, partly because of increasing global temperatures.
INFLUENCE OF NATURAL CATASTROPHES
Volcanic eruptions affect global climate by releasing sulfur dioxide (which can form sulfuric acid) and ash into the air. As aerosols (floating particles) these reflect some sunlight back into space; cooling Earth. In 1991, the Pinatubo eruption lowered average temperatures by 32.9°F (0.5°C) for two years.
An asteroid strike works similarly: the impact raises clouds of dust that act as atmospheric aerosols. About 65 million years ago, a huge asteroid or comet struck Mexico, causing climatic cooling, which led to mass extinction. Of course, supervol-cano eruptions and asteroid collisions are extremely rare and are not behind the recent warming trend.