Slow vs. Abrupt Climate Change
Studying the Little Ice Age for Clues on Rapid Climate Transition
Climate changes occur as part of the Earth's normal climate cycle, in a slow transitional method. Abrupt climate change has happened in the past due to various effects.
Discover how scientists study climate change, using ice cores to determine the length of periods of warming and cooling. Learn how the Little Ice Age occurred, what the Great Ocean Conveyor does and what it means for future climate change.
Earth’s Climate Cycle
Studies on climate have established that the Earth’s climate is a repeatable cycle of warm and cool periods. These climate changes are more of a slow transition than an abrupt change. The Earth goes through periods of interglacial, warm and then colder, glacial periods. Currently, we are experiencing an interglacial share of the climate cycle.
Scientists have found that the Earth’s climate cycle is related to its tilt, as the Earth orbits the sun on a rotational axis. This concept is known as the Milankovitch Theory, developed by Milutin Milankovitch in 1938.
Does Abrupt Climate Change Occur?
Evidence of abrupt climate change has been revealed. Ice cores reveal these divergent changes, representing rapid transitions between warm and cold environments. The Woods Hole Oceanographic Institution describes one of the most evident examples of these events, known as the Younger Dryas event.
The Younger Dryas occurred about 12,000 years ago. Evidence shows that the event began with a transition to cooler temperatures and ended within a decade. However, cooler temperatures resulted for 1,000 years after the event. According to the institution, the “North Atlantic region was about 5 degree Celsius colder” for that thousand year period.
It is still debated as to whether the Younger Dryas event was a result of orbital force or other causes. Another explanation theorized has been ocean dynamics, which deals with the “Great Ocean Conveyor” that transports heat around the world through ocean currents. This system determines climate stability and transition. Slight changes in salinity or temperature can result in a slowdown of the ocean conveyor, causing rapid climate changes.
Examining the Little Ice Age
The Little Ice Age occurred from the early 1400s until the late 1800s, affecting many areas of the Northern Hemisphere. Regions of North America and Europe experienced the lowest temperature values of the last millennium, according to the climatology records. Winter temperatures dipped by 2 to 3 degrees Fahrenheit, or 1-1.5 Celsius. The most popular theory posed to explain why the Little Ice Age occurred deals with a period of low solar activity.
Astronomers during this period recorded the sun’s activity, counting the number of sunspots for a 30 year period. Normal sun activity recorded 40-50,000 sunspots in a 30 year period. During the coldest portion of the Little Ice Age, from 1645 to 1715, astronomers observed about 50 sunspots for a 30 year period, which points to a definite decline in solar activity. This period is known as the Maunder Minimum.
Low solar activity affected the climate system, yet took some time for its full effects to be felt. Scientists estimate a 10-30 year lag time from the Maunder Minimum.
Could it Happen Again?
Although variations in the sun’s output seem to have resulted in the Little Ice Age, it is the human affect on climate that poses the most harm to the planet. Scientists now study models explaining how global warming could cause a colder climate, due to elevated ocean temperatures and increased saltiness of some tropical regions. These small changes can result in abrupt climate transitions, as the Great Ocean Conveyor slows.
Sources
Woods Hole Oceanographic Institution
NASA Goddard Space Flight Center
